--- 1/draft-ietf-cellar-ffv1-00.txt 2018-01-26 16:13:14.245330091 -0800 +++ 2/draft-ietf-cellar-ffv1-01.txt 2018-01-26 16:13:14.325332003 -0800 @@ -1,153 +1,154 @@ cellar M. Niedermayer Internet-Draft Intended status: Standards Track D. Rice -Expires: January 3, 2018 +Expires: July 30, 2018 J. Martinez - July 2, 2017 + January 26, 2018 FF Video Codec 1 - draft-ietf-cellar-ffv1-00 + draft-ietf-cellar-ffv1-01 Abstract This document defines FFV1, a lossless intra-frame video encoding format. FFV1 is designed to efficiently compress video data in a variety of pixel formats. Compared to uncompressed video, FFV1 offers storage compression, frame fixity, and self-description, which makes FFV1 useful as a preservation or intermediate video format. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- - Drafts is at http://datatracker.ietf.org/drafts/current/. + Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on January 3, 2018. + This Internet-Draft will expire on July 30, 2018. Copyright Notice - Copyright (c) 2017 IETF Trust and the persons identified as the + Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents - (http://trustee.ietf.org/license-info) in effect on the date of + (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Notation and Conventions . . . . . . . . . . . . . . . . . . 4 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5 2.2.1. Arithmetic operators . . . . . . . . . . . . . . . . 5 2.2.2. Assignment operators . . . . . . . . . . . . . . . . 6 2.2.3. Comparison operators . . . . . . . . . . . . . . . . 6 - 2.2.4. Mathematical functions . . . . . . . . . . . . . . . 6 + 2.2.4. Mathematical functions . . . . . . . . . . . . . . . 7 2.2.5. Order of operation precedence . . . . . . . . . . . . 7 - 2.2.6. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 7 - 2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 7 + 2.2.6. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 8 + 2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 8 2.2.9. Bitstream functions . . . . . . . . . . . . . . . . . 8 3. General Description . . . . . . . . . . . . . . . . . . . . . 8 - 3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 8 + 3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 3.3. Median predictor . . . . . . . . . . . . . . . . . . . . 9 + 3.3. Median predictor . . . . . . . . . . . . . . . . . . . . 10 3.4. Context . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 3.5. Quantization Table Sets . . . . . . . . . . . . . . . . . 10 + 3.5. Quantization Table Sets . . . . . . . . . . . . . . . . . 11 3.6. Quantization Table Set indexes . . . . . . . . . . . . . 11 - 3.7. Color space . . . . . . . . . . . . . . . . . . . . . . . 11 - 3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 11 - 3.7.2. JPEG2000-RCT . . . . . . . . . . . . . . . . . . . . 12 - 3.8. Coding of the Sample Difference . . . . . . . . . . . . . 13 - 3.8.1. Range coding mode . . . . . . . . . . . . . . . . . . 13 - 3.8.2. Huffman coding mode . . . . . . . . . . . . . . . . . 17 + 3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 12 + 3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 12 + 3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 3.8. Coding of the Sample Difference . . . . . . . . . . . . . 14 + 3.8.1. Range coding mode . . . . . . . . . . . . . . . . . . 14 + 3.8.2. Golomb Rice mode . . . . . . . . . . . . . . . . . . 17 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.1. Configuration Record . . . . . . . . . . . . . . . . . . 20 4.1.1. reserved_for_future_use . . . . . . . . . . . . . . . 21 4.1.2. configuration_record_crc_parity . . . . . . . . . . . 21 4.1.3. Mapping FFV1 into Containers . . . . . . . . . . . . 21 4.2. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.3. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.4. Slice Header . . . . . . . . . . . . . . . . . . . . . . 23 4.4.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 23 4.4.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 23 - 4.4.3. slice_width . . . . . . . . . . . . . . . . . . . . . 23 - 4.4.4. slice_height . . . . . . . . . . . . . . . . . . . . 23 - 4.4.5. quant_table_set_index_count . . . . . . . . . . . . . 23 + 4.4.3. slice_width . . . . . . . . . . . . . . . . . . . . . 24 + 4.4.4. slice_height . . . . . . . . . . . . . . . . . . . . 24 + 4.4.5. quant_table_set_index_count . . . . . . . . . . . . . 24 4.4.6. quant_table_set_index . . . . . . . . . . . . . . . . 24 4.4.7. picture_structure . . . . . . . . . . . . . . . . . . 24 4.4.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 24 - 4.4.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 24 - 4.4.10. reset_contexts . . . . . . . . . . . . . . . . . . . 24 - 4.4.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 24 + 4.4.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 25 + 4.4.10. reset_contexts . . . . . . . . . . . . . . . . . . . 25 + 4.4.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 25 4.5. Slice Content . . . . . . . . . . . . . . . . . . . . . . 25 4.5.1. primary_color_count . . . . . . . . . . . . . . . . . 25 - 4.5.2. plane_pixel_height . . . . . . . . . . . . . . . . . 25 - 4.5.3. slice_pixel_height . . . . . . . . . . . . . . . . . 25 - 4.5.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 25 - 4.6. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 25 + 4.5.2. plane_pixel_height . . . . . . . . . . . . . . . . . 26 + 4.5.3. slice_pixel_height . . . . . . . . . . . . . . . . . 26 + 4.5.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 26 + 4.6. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.6.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 26 - 4.6.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 26 - 4.6.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 26 - 4.7. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 26 + 4.6.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 27 + 4.6.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 27 + 4.6.4. sample_difference . . . . . . . . . . . . . . . . . . 27 + 4.7. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 27 4.7.1. slice_size . . . . . . . . . . . . . . . . . . . . . 27 4.7.2. error_status . . . . . . . . . . . . . . . . . . . . 27 - 4.7.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 27 - 4.8. Parameters . . . . . . . . . . . . . . . . . . . . . . . 27 - 4.8.1. version . . . . . . . . . . . . . . . . . . . . . . . 28 - 4.8.2. micro_version . . . . . . . . . . . . . . . . . . . . 29 - 4.8.3. coder_type . . . . . . . . . . . . . . . . . . . . . 30 - 4.8.4. state_transition_delta . . . . . . . . . . . . . . . 30 - 4.8.5. colorspace_type . . . . . . . . . . . . . . . . . . . 30 - 4.8.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 30 - 4.8.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 31 - 4.8.8. h_chroma_subsample . . . . . . . . . . . . . . . . . 31 - 4.8.9. v_chroma_subsample . . . . . . . . . . . . . . . . . 31 - 4.8.10. alpha_plane . . . . . . . . . . . . . . . . . . . . . 31 - 4.8.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 31 - 4.8.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 32 - 4.8.13. quant_table_set_count . . . . . . . . . . . . . . . . 32 - 4.8.14. states_coded . . . . . . . . . . . . . . . . . . . . 32 - 4.8.15. initial_state_delta . . . . . . . . . . . . . . . . . 32 - 4.8.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 32 - 4.8.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 32 - 4.9. Quantization Table Set . . . . . . . . . . . . . . . . . 33 - 4.9.1. quant_tables . . . . . . . . . . . . . . . . . . . . 34 - 4.9.2. context_count . . . . . . . . . . . . . . . . . . . . 34 - 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 34 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 35 - 7. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . 35 - 7.1. Decoder implementation suggestions . . . . . . . . . . . 36 - 7.1.1. Multi-threading support and independence of slices . 36 - 8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 36 - 9. ToDo . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 37 - 10.1. Normative References . . . . . . . . . . . . . . . . . . 37 - 10.2. Informative References . . . . . . . . . . . . . . . . . 37 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39 + 4.7.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 28 + 4.8. Parameters . . . . . . . . . . . . . . . . . . . . . . . 28 + 4.8.1. version . . . . . . . . . . . . . . . . . . . . . . . 29 + 4.8.2. micro_version . . . . . . . . . . . . . . . . . . . . 30 + 4.8.3. coder_type . . . . . . . . . . . . . . . . . . . . . 31 + 4.8.4. state_transition_delta . . . . . . . . . . . . . . . 31 + 4.8.5. colorspace_type . . . . . . . . . . . . . . . . . . . 31 + 4.8.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 32 + 4.8.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 32 + 4.8.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 32 + 4.8.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 32 + 4.8.10. alpha_plane . . . . . . . . . . . . . . . . . . . . . 32 + 4.8.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 33 + 4.8.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 33 + 4.8.13. quant_table_set_count . . . . . . . . . . . . . . . . 33 + 4.8.14. states_coded . . . . . . . . . . . . . . . . . . . . 33 + 4.8.15. initial_state_delta . . . . . . . . . . . . . . . . . 33 + 4.8.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 33 + 4.8.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 34 + 4.9. Quantization Table Set . . . . . . . . . . . . . . . . . 34 + 4.9.1. quant_tables . . . . . . . . . . . . . . . . . . . . 35 + 4.9.2. context_count . . . . . . . . . . . . . . . . . . . . 35 + 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 35 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 36 + 7. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . 36 + 7.1. Decoder implementation suggestions . . . . . . . . . . . 37 + 7.1.1. Multi-threading support and independence of slices . 37 + 8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 37 + 9. ToDo . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 + 10.1. Normative References . . . . . . . . . . . . . . . . . . 38 + 10.2. Informative References . . . . . . . . . . . . . . . . . 38 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 1. Introduction This document describes FFV1, a lossless video encoding format. The design of FFV1 considers the storage of image characteristics, data fixity, and the optimized use of encoding time and storage requirements. FFV1 is designed to support a wide range of lossless video applications such as long-term audiovisual preservation, scientific imaging, screen recording, and other video encoding scenarios that seek to avoid the generational loss of lossy video @@ -180,39 +181,49 @@ [YCbCr]. 2. Notation and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2.1. Definitions + "Sample": The smallest addressable representation of a color + component or a luma component in a frame. Examples of sample are + Luma, Blue Chrominance, Red Chrominance, Alpha, Red, Green, Blue. + + "Pixel": The smallest addressable representation of a color in a + frame. It is composed of 1 or more samples. + "ESC": An ESCape symbol to indicate that the symbol to be stored is too large for normal storage and that an alternate storage method. "MSB": Most Significant Bit, the bit that can cause the largest change in magnitude of the symbol. "RCT": Reversible Color Transform, a near linear, exactly reversible integer transform that converts between RGB and YCbCr representations - of a sample. + of a Pixel. "VLC": Variable Length Code, a code which maps source symbols to a variable number of bits. - "RGB": A reference to the method of storing the value of a sample by + "RGB": A reference to the method of storing the value of a Pixel by using three numeric values that represent Red, Green, and Blue. - "YCbCr": A reference to the method of storing the value of a sample - by using three numeric values that represent the luminance of the - sample (Y) and the chrominance of the sample (Cb and Cr). + "YCbCr": A reference to the method of storing the value of a Pixel by + using three numeric values that represent the luma of the Pixel (Y) + and the chrominance of the Pixel (Cb and Cr). YCbCr word is used for + historical reasons and currently references any color space relying + on 1 luma and 2 chrominances e.g. YCbCr, YCgCo or ICtCp. Exact + meaning of the three numeric values is unspecified. "TBA": To Be Announced. Used in reference to the development of future iterations of the FFV1 specification. 2.2. Conventions Note: the operators and the order of precedence are the same as used in the C programming language [ISO.9899.1990]. 2.2.1. Arithmetic operators @@ -327,54 +339,62 @@ programming language [ISO.9899.1990] as uses its "if/else", "while" and "for" functions as well as functions defined within this document. 2.2.7. Range "a...b" means any value starting from a to b, inclusive. 2.2.8. NumBytes - NumBytes is a non-negative integer that expresses the size in 8-bit - octets of particular FFV1 components such as the Configuration Record - and Frame. FFV1 relies on its container to store the NumBytes - values, see Section 4.1.3. + "NumBytes" is a non-negative integer that expresses the size in 8-bit + octets of particular FFV1 components such as the "Configuration + Record" and "Frame". FFV1 relies on its container to store the + "NumBytes" values, see Section 4.1.3. 2.2.9. Bitstream functions 2.2.9.1. remaining_bits_in_bitstream "remaining_bits_in_bitstream( )" means the count of remaining bits - after the current position in that bitstream component. It is - computed from the NumBytes value multiplied by 8 minus the count of - bits of that component already read by the bitstream parser. + after the pointer in that bitstream component. It is computed from + the "NumBytes" value multiplied by 8 minus the count of bits of that + component already read by the bitstream parser. 2.2.9.2. byte_aligned "byte_aligned( )" is true if "remaining_bits_in_bitstream( NumBytes )" is a multiple of 8, otherwise false. +2.2.9.3. get_bits + + "get_bits( i )" is the action to read the next "i" bits in the + bitstream, from most significant bit to least significant bit, and to + return the corresponding value. The pointer is increased by "i". + 3. General Description Samples within a plane are coded in raster scan order (left->right, top->bottom). Each sample is predicted by the median predictor from samples in the same plane and the difference is stored see Section 3.8. 3.1. Border A border is assumed for each coded slice for the purpose of the predictor and context according to the following rules: o one column of samples to the left of the coded slice is assumed as identical to the samples of the leftmost column of the coded slice - shifted down by one row + shifted down by one row. The value of the topmost sample of the + column of samples to the left of the coded slice is assumed to be + "0" o one column of samples to the right of the coded slice is assumed as identical to the samples of the rightmost column of the coded slice o an additional column of samples to the left of the coded slice and two rows of samples above the coded slice are assumed to be "0" The following table depicts a slice of samples "a,b,c,d,e,f,g,h,i" along with its assumed border. @@ -398,88 +418,87 @@ Positions used for context and median predictor are: +---+---+---+---+ | | | T | | +---+---+---+---+ | |tl | t |tr | +---+---+---+---+ | L | l | X | | +---+---+---+---+ - "X" is the current processed Sample. - The identifers are made of the first letters of the words Top, Left - and Right. + "X" is the current processed Sample. The identifiers are made of the + first letters of the words Top, Left and Right. 3.3. Median predictor The prediction for any sample value at position "X" may be computed based upon the relative neighboring values of "l", "t", and "tl" via this equation: "median(l, t, l + t - tl)". Note, this prediction template is also used in [ISO.14495-1.1999] and [HuffYUV]. - Exception for the media predictor: if colorspace_type == 0 && - bits_per_raw_sample == 16 && ( coder_type == 1 || coder_type == 2 ), + Exception for the media predictor: if "colorspace_type == 0 && + bits_per_raw_sample == 16 && ( coder_type == 1 || coder_type == 2 )", the following media predictor MUST be used: "median(left16s, top16s, left16s + top16s - diag16s)" where: left16s = l >= 32768 ? ( l - 65536 ) : l top16s = t >= 32768 ? ( t - 65536 ) : t diag16s = tl >= 32768 ? ( tl - 65536 ) : tl Background: a two's complement signed 16-bit signed integer was used - for storing pixel values in all known implementations of FFV1 + for storing sample values in all known implementations of FFV1 bitstream. So in some circumstances, the most significant bit was wrongly interpreted (used as a sign bit instead of the 16th bit of an unsigned integer). Note that when the issue is discovered, the only configuration of all known implementations being impacted is 16-bit - YCbCr color space with Range Coder coder, as other potentially - impacted configurations (e.g. 15/16-bit JPEG2000-RCT color space with - Range Coder coder, or 16-bit any color space with Golomb Rice coder) - were implemented nowhere. In the meanwhile, 16-bit JPEG2000-RCT - color space with Range Coder coder was implemented without this issue - in one implementation and validated by one conformance checker. It - is expected (to be confirmed) to remove this exception for the media - predictor in the next version of the bitstream. + YCbCr with no Pixel transformation with Range Coder coder, as other + potentially impacted configurations (e.g. 15/16-bit JPEG2000-RCT with + Range Coder coder, or 16-bit content with Golomb Rice coder) were + implemented nowhere. In the meanwhile, 16-bit JPEG2000-RCT with + Range Coder coder was implemented without this issue in one + implementation and validated by one conformance checker. It is + expected (to be confirmed) to remove this exception for the media + predictor in the next version of the FFV1 bitstream. 3.4. Context Relative to any sample "X", the Quantized Sample Differences "L-l", "l-tl", "tl-t", "T-t", and "t-tr" are used as context: context = Q_{0}[l - tl] + Q_{1}[tl - t] + Q_{2}[t - tr] + Q_{3}[L - l] + Q_{4}[T - t] If "context >= 0" then "context" is used and the difference between the sample and its predicted value is encoded as is, else "-context" is used and the difference between the sample and its predicted value is encoded with a flipped sign. 3.5. Quantization Table Sets - The bitstream contains 1 or more Quantization Table Sets. - Each Quantization Table Set contains exactly 5 Quantization Tables, - each Quantization Table corresponding to 1 of the 5 Quantized Sample - Differences. - For each Quantization Table, both the number of quantization steps - and their distribution are stored in the bitstream; each Quantization - Table has exactly 256 entries, and the 8 least significant bits of - the Quantized Sample Difference are used as index: + The FFV1 bitstream contains 1 or more Quantization Table Sets. Each + Quantization Table Set contains exactly 5 Quantization Tables, each + Quantization Table corresponding to 1 of the 5 Quantized Sample + Differences. For each Quantization Table, both the number of + quantization steps and their distribution are stored in the FFV1 + bitstream; each Quantization Table has exactly 256 entries, and the 8 + least significant bits of the Quantized Sample Difference are used as + index: Q_{j}[k] = quant_tables[i][j][k&255] In this formula, "i" is the Quantization Table Set index, "j" is the Quantized Table index, "k" the Quantized Sample Difference. 3.6. Quantization Table Set indexes For each plane of each slice, a Quantization Table Set is selected from an index: @@ -487,121 +506,113 @@ o For Y plane, "quant_table_set_index [ 0 ]" index is used o For Cb and Cr planes, "quant_table_set_index [ 1 ]" index is used o For Alpha plane, "quant_table_set_index [ (version <= 3 || chroma_planes) ? 2 : 1 ]" index is used Background: in first implementations of FFV1 bitstream, the index for Cb and Cr planes was stored even if it is not used (chroma_planes set to 0), this index is kept for version <= 3 in order to keep - compatibility with bitstreams in the wild. + compatibility with FFV1 bitstreams in the wild. -3.7. Color space +3.7. Color spaces - FFV1 supports two color spaces: YCbCr and JPEG2000-RCT. Both color - spaces allow an optional Alpha plane that can be used to code - transparency data. + FFV1 supports two color spaces: YCbCr and RGB. Both color spaces + allow an optional Alpha plane that can be used to code transparency + data. 3.7.1. YCbCr In YCbCr color space, the Cb and Cr planes are optional, but if used then MUST be used together. Omitting the Cb and Cr planes codes the - frames in grayscale without color data. An FFV1 frame using YCbCr + frames in grayscale without color data. An FFV1 "Frame" using YCbCr MUST use one of the following arrangements: o Y o Y, Alpha o Y, Cb, Cr o Y, Cb, Cr, Alpha - When FFV1 uses the YCbCr color space, the Y plane MUST be coded - first. If the Cb and Cr planes are used then they MUST be coded - after the Y plane. If an Alpha (transparency) plane is used, then it - MUST be coded last. + The Y plane MUST be coded first. If the Cb and Cr planes are used + then they MUST be coded after the Y plane. If an Alpha + (transparency) plane is used, then it MUST be coded last. -3.7.2. JPEG2000-RCT +3.7.2. RGB JPEG2000-RCT is a Reversible Color Transform that codes RGB (red, green, blue) planes losslessly in a modified YCbCr color space. - Reversible conversions between YCbCr and RGB use the following - formulae. + Reversible Pixel transformations between YCbCr and RGB use the + following formulae. Cb=b-g Cr=r-g Y=g+(Cb+Cr)>>2 g=Y-(Cb+Cr)>>2 r=Cr+g b=Cb+g - Exception for the reversible conversions between YCbCr and RGB: if - bits_per_raw_sample is between 9 and 15 inclusive, the following - formulae for reversible conversions between YCbCr and RGB MUST be - used instead of the ones above: + Exception for the JPEG2000-RCT conversion: if bits_per_raw_sample is + between 9 and 15 inclusive, the following formulae for reversible + conversions between YCbCr and RGB MUST be used instead of the ones + above: Cb=g-b Cr=r-b Y=b+(Cb+Cr)>>2 b=Y-(Cb+Cr)>>2 r=Cr+b g=Cb+b Background: At the time of this writing, in all known implementations of FFV1 bitstream, when bits_per_raw_sample was between 9 and 15 inclusive, GBR planes were used as BGR planes during both encoding - and decoding. In the meanwhile, 16-bit JPEG2000-RCT color space was - implemented without this issue in one implementation and validated by - one conformance checker. Methods to address this exception for the - transform are under consideration for the next version of the + and decoding. In the meanwhile, 16-bit JPEG2000-RCT was implemented + without this issue in one implementation and validated by one + conformance checker. Methods to address this exception for the + transform are under consideration for the next version of the FFV1 bitstream. [ISO.15444-1.2016] - An FFV1 frame using JPEG2000-RCT MUST use one of the following - arrangements: - o Y, Cb, Cr - - o Y, Cb, Cr, Alpha - - When FFV1 uses the JPEG2000-RCT color space, the horizontal lines are - interleaved to improve caching efficiency since it is most likely - that the RCT will immediately be converted to RGB during decoding. - The interleaved coding order is also Y, then Cb, then Cr, and then if + When FFV1 uses the JPEG2000-RCT, the horizontal lines are interleaved + to improve caching efficiency since it is most likely that the RCT + will immediately be converted to RGB during decoding. The + interleaved coding order is also Y, then Cb, then Cr, and then if used Alpha. - As an example, a frame that is two pixels wide and two pixels high, + As an example, a "Frame" that is two pixels wide and two pixels high, could be comprised of the following structure: +------------------------+------------------------+ | Pixel[1,1] | Pixel[2,1] | | Y[1,1] Cb[1,1] Cr[1,1] | Y[2,1] Cb[2,1] Cr[2,1] | +------------------------+------------------------+ | Pixel[1,2] | Pixel[2,2] | | Y[1,2] Cb[1,2] Cr[1,2] | Y[2,2] Cb[2,2] Cr[2,2] | +------------------------+------------------------+ - In JPEG2000-RCT color space, the coding order would be left to right - and then top to bottom, with values interleaved by lines and stored - in this order: + In JPEG2000-RCT, the coding order would be left to right and then top + to bottom, with values interleaved by lines and stored in this order: Y[1,1] Y[2,1] Cb[1,1] Cb[2,1] Cr[1,1] Cr[2,1] Y[1,2] Y[2,2] Cb[1,2] Cb[2,2] Cr[1,2] Cr[2,2] 3.8. Coding of the Sample Difference Instead of coding the n+1 bits of the Sample Difference with Huffman or Range coding (or n+2 bits, in the case of RCT), only the n (or n+1) least significant bits are used, since this is sufficient to recover the original sample. In the equation below, the term "bits" @@ -774,29 +785,30 @@ 175,189,179,181,186,183,192,185,200,187,191,188,190,197,193,196, 197,194,195,196,198,202,199,201,210,203,207,204,205,206,208,214, 209,211,221,212,213,215,224,216,217,218,219,220,222,228,223,225, 226,224,227,229,240,230,231,232,233,234,235,236,238,239,237,242, 241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255, -3.8.2. Huffman coding mode +3.8.2. Golomb Rice mode - This coding mode uses Golomb Rice codes. The VLC code is split into - 2 parts, the prefix stores the most significant bits, the suffix - stores the k least significant bits or stores the whole number in the - ESC case. The end of the bitstream (of the frame) is filled with - 0-bits until that the bitstream contains a multiple of 8 bits. + This coding mode uses Golomb Rice codes. The VLC is split into 2 + parts, the prefix stores the most significant bits, the suffix stores + the k least significant bits or stores the whole number in the ESC + case. The end of the bitstream of the "Frame" is filled with 0-bits + until that the bitstream contains a multiple of 8 bits. 3.8.2.1. Prefix + +----------------+-------+ | bits | value | +----------------+-------+ | 1 | 0 | | 01 | 1 | | ... | ... | | 0000 0000 0001 | 11 | | 0000 0000 0000 | ESC | +----------------+-------+ @@ -842,21 +854,21 @@ log2_run[41]={ | 0, 0, 0, 0, 1, 1, 1, 1, | 2, 2, 2, 2, 3, 3, 3, 3, | 4, 4, 5, 5, 6, 6, 7, 7, | 8, 9,10,11,12,13,14,15, | 16,17,18,19,20,21,22,23, | 24, | }; | | if (run_count == 0 && run_mode == 1) { | - if (get_bits1()) { | + if (get_bits(1)) { | run_count = 1 << log2_run[run_index]; | if (x + run_count <= w) | run_index++; | } else { | if (log2_run[run_index]) | run_count = get_bits(log2_run[run_index]); | else | run_count = 0; | if (run_index) | run_index--; | @@ -893,112 +905,117 @@ | sr | Range coded signed scalar symbol coded with the method | | | described in Section 3.8.1.2 | +--------+----------------------------------------------------------+ The same context which is initialized to 128 is used for all fields in the header. The following MUST be provided by external means during initialization of the decoder: - "frame_pixel_width" is defined as frame width in pixels. + "frame_pixel_width" is defined as "Frame" width in pixels. - "frame_pixel_height" is defined as frame height in pixels. + "frame_pixel_height" is defined as "Frame" height in pixels. Default values at the decoder initialization phase: "ConfigurationRecordIsPresent" is set to 0. 4.1. Configuration Record - In the case of a bitstream with "version >= 3", a Configuration - Record is stored in the underlying container, at the track header - level. It contains the parameters used for all frames. The size of - the Configuration Record, NumBytes, is supplied by the underlying - container. + In the case of a FFV1 bitstream with "version >= 3", a "Configuration + Record" is stored in the underlying container, at the track header + level. It contains the parameters used for all instances of "Frame". + The size of the "Configuration Record", "NumBytes", is supplied by + the underlying container. pseudo-code | type --------------------------------------------------------------|----- ConfigurationRecord( NumBytes ) { | ConfigurationRecordIsPresent = 1 | Parameters( ) | while( remaining_bits_in_bitstream( NumBytes ) > 32 ) | reserved_for_future_use | u(1) configuration_record_crc_parity | u(32) } | 4.1.1. reserved_for_future_use "reserved_for_future_use" has semantics that are reserved for future - use. Encoders conforming to this version of this specification - SHALL NOT write this value. Decoders conforming to this version of - this specification SHALL ignore its value. + use. + Encoders conforming to this version of this specification SHALL NOT + write this value. + Decoders conforming to this version of this specification SHALL + ignore its value. 4.1.2. configuration_record_crc_parity "configuration_record_crc_parity" 32 bits that are chosen so that the - Configuration Record as a whole has a crc remainder of 0. This is - equivalent to storing the crc remainder in the 32-bit parity. The - CRC generator polynomial used is the standard IEEE CRC polynomial + "Configuration Record" as a whole has a crc remainder of 0. + This is equivalent to storing the crc remainder in the 32-bit parity. + The CRC generator polynomial used is the standard IEEE CRC polynomial (0x104C11DB7) with initial value 0. 4.1.3. Mapping FFV1 into Containers - This Configuration Record can be placed in any file format supporting - Configuration Records, fitting as much as possible with how the file - format uses to store Configuration Records. The Configuration Record - storage place and NumBytes are currently defined and supported by - this version of this specification for the following container - formats: + This "Configuration Record" can be placed in any file format + supporting "Configuration Records", fitting as much as possible with + how the file format uses to store "Configuration Records". The + "Configuration Record" storage place and "NumBytes" are currently + defined and supported by this version of this specification for the + following container formats: -4.1.3.1. In AVI File Format +4.1.3.1. AVI File Format - The Configuration Record extends the stream format chunk ("AVI ", - "hdlr", "strl", "strf") with the ConfigurationRecord bitstream. See - [AVI] for more information about chunks. + The "Configuration Record" extends the stream format chunk ("AVI ", + "hdlr", "strl", "strf") with the ConfigurationRecord bitstream. + See [AVI] for more information about chunks. "NumBytes" is defined as the size, in bytes, of the strf chunk indicated in the chunk header minus the size of the stream format structure. -4.1.3.2. In ISO/IEC 14496-12 (MP4 File Format) +4.1.3.2. ISO Base Media File Format - The Configuration Record extends the sample description box ("moov", - "trak", "mdia", "minf", "stbl", "stsd") with a "glbl" box which - contains the ConfigurationRecord bitstream. See [ISO.14496-12.2015] - for more information about boxes. + The "Configuration Record" extends the sample description box + ("moov", "trak", "mdia", "minf", "stbl", "stsd") with a "glbl" box + which contains the ConfigurationRecord bitstream. See + [ISO.14496-12.2015] for more information about boxes. "NumBytes" is defined as the size, in bytes, of the "glbl" box indicated in the box header minus the size of the box header. -4.1.3.3. In NUT File Format +4.1.3.3. NUT File Format The codec_specific_data element (in "stream_header" packet) contains the ConfigurationRecord bitstream. See [NUT] for more information about elements. "NumBytes" is defined as the size, in bytes, of the codec_specific_data element as indicated in the "length" field of codec_specific_data -4.1.3.4. In Matroska File Format +4.1.3.4. Matroska File Format FFV1 SHOULD use "V_FFV1" as the Matroska "Codec ID". For FFV1 versions 2 or less, the Matroska "CodecPrivate" Element SHOULD NOT be used. For FFV1 versions 3 or greater, the Matroska "CodecPrivate" - Element MUST contain the FFV1 Configuration Record structure and no + Element MUST contain the FFV1 "Configuration Record" structure and no other data. See [Matroska] for more information about elements. + "NumBytes" is defined as the "Element Data Size" of the + "CodecPrivate" Element. + 4.2. Frame - A frame consists of the keyframe field, parameters (if version <=1), - and a sequence of independent slices. + A "Frame" consists of the keyframe field, parameters (if version + <=1), and a sequence of independent slices. pseudo-code | type --------------------------------------------------------------|----- Frame( NumBytes ) { | keyframe | br if (keyframe && !ConfigurationRecordIsPresent | Parameters( ) | while ( remaining_bits_in_bitstream( NumBytes ) ) | Slice( ) | } | @@ -1036,224 +1053,241 @@ sar_den | ur if (version >= 4) { | reset_contexts | br slice_coding_mode | ur } | } | 4.4.1. slice_x "slice_x" indicates the x position on the slice raster formed by - num_h_slices. Inferred to be 0 if not present. + num_h_slices. + Inferred to be 0 if not present. 4.4.2. slice_y "slice_y" indicates the y position on the slice raster formed by - num_v_slices. Inferred to be 0 if not present. + num_v_slices. + Inferred to be 0 if not present. 4.4.3. slice_width "slice_width" indicates the width on the slice raster formed by - num_h_slices. Inferred to be 1 if not present. + num_h_slices. + Inferred to be 1 if not present. 4.4.4. slice_height "slice_height" indicates the height on the slice raster formed by - num_v_slices. Inferred to be 1 if not present. + num_v_slices. + Inferred to be 1 if not present. 4.4.5. quant_table_set_index_count - "quant_table_set_index_count" is defined as 1 + ( ( chroma_planes || - version <= 3 ) ? 1 : 0 ) + ( alpha_plane ? 1 : 0 ). + "quant_table_set_index_count" is defined as "1 + ( ( chroma_planes || + version \<= 3 ) ? 1 : 0 ) + ( alpha_plane ? 1 : 0 )". 4.4.6. quant_table_set_index "quant_table_set_index" indicates the Quantization Table Set index to select the Quantization Table Set and the initial states for the - slice. Inferred to be 0 if not present. + slice. + Inferred to be 0 if not present. 4.4.7. picture_structure - "picture_structure" specifies the picture structure. Inferred to be - 0 if not present. + "picture_structure" specifies the temporal and spatial relationship + of each line of the "Frame". + Inferred to be 0 if not present. +-------+-------------------------+ | value | picture structure used | +-------+-------------------------+ | 0 | unknown | | 1 | top field first | | 2 | bottom field first | | 3 | progressive | | Other | reserved for future use | +-------+-------------------------+ 4.4.8. sar_num - "sar_num" specifies the sample aspect ratio numerator. Inferred to - be 0 if not present. MUST be 0 if sample aspect ratio is unknown. + "sar_num" specifies the sample aspect ratio numerator. + Inferred to be 0 if not present. + MUST be 0 if sample aspect ratio is unknown. 4.4.9. sar_den - "sar_den" specifies the sample aspect ratio numerator. Inferred to - be 0 if not present. MUST be 0 if sample aspect ratio is unknown. + "sar_den" specifies the sample aspect ratio numerator. + Inferred to be 0 if not present. + MUST be 0 if sample aspect ratio is unknown. 4.4.10. reset_contexts - "reset_contexts" indicates if slice contexts must be reset. Inferred - to be 0 if not present. + "reset_contexts" indicates if slice contexts must be reset. + Inferred to be 0 if not present. 4.4.11. slice_coding_mode - "slice_coding_mode" indicates the slice coding mode. Inferred to be - 0 if not present. + "slice_coding_mode" indicates the slice coding mode. + Inferred to be 0 if not present. - +-------+----------------------------+ + +-------+-----------------------------+ | value | slice coding mode | - +-------+----------------------------+ - | 0 | normal Range Coding or VLC | + +-------+-----------------------------+ + | 0 | Range Coding or Golomb Rice | | 1 | raw PCM | | Other | reserved for future use | - +-------+----------------------------+ + +-------+-----------------------------+ 4.5. Slice Content pseudo-code | type --------------------------------------------------------------|----- SliceContent( ) { | if (colorspace_type == 0) { | - for( p = 0; p < primary_color_count; p++ ) { | + for( p = 0; p < primary_color_count; p++ ) | for( y = 0; y < plane_pixel_height[ p ]; y++ ) | Line( p, y ) | } else if (colorspace_type == 1) { | for( y = 0; y < slice_pixel_height; y++ ) | - for( p = 0; p < primary_color_count; p++ ) { | + for( p = 0; p < primary_color_count; p++ ) | Line( p, y ) | } | } | 4.5.1. primary_color_count "primary_color_count" is defined as 1 + ( chroma_planes ? 2 : 0 ) + ( alpha_plane ? 1 : 0 ). 4.5.2. plane_pixel_height "plane_pixel_height[ p ]" is the height in pixels of plane p of the - slice. "plane_pixel_height[ 0 ]" and "plane_pixel_height[ 1 + ( - chroma_planes ? 2 : 0 ) ]" value is "slice_pixel_height". If - "chroma_planes" is set to 1, "plane_pixel_height[ 1 ]" and + slice. + "plane_pixel_height[ 0 ]" and "plane_pixel_height[ 1 + ( + chroma_planes ? 2 : 0 ) ]" value is "slice_pixel_height". + If "chroma_planes" is set to 1, "plane_pixel_height[ 1 ]" and "plane_pixel_height[ 2 ]" value is "ceil(slice_pixel_height / - v_chroma_subsample)". + log2_v_chroma_subsample)". 4.5.3. slice_pixel_height - "slice_pixel_height" is the height in pixels of the slice. Its value - is "floor(( slice_y + slice_height ) * slice_pixel_height / + "slice_pixel_height" is the height in pixels of the slice. + Its value is "floor(( slice_y + slice_height ) * slice_pixel_height / num_v_slices) - slice_pixel_y". 4.5.4. slice_pixel_y - "slice_pixel_y" is the slice vertical position in pixels. Its value - is "floor(slice_y * frame_pixel_height / num_v_slices)". + "slice_pixel_y" is the slice vertical position in pixels. + Its value is "floor(slice_y * frame_pixel_height / num_v_slices)". 4.6. Line + pseudo-code | type --------------------------------------------------------------|----- Line( p, y ) { | if (colorspace_type == 0) { | for( x = 0; x < plane_pixel_width[ p ]; x++ ) | - Pixel( p, y, x ) | + sample_difference[ p ][ y ][ x ] | } else if (colorspace_type == 1) { | for( x = 0; x < slice_pixel_width; x++ ) | - Pixel( p, y, x ) | + sample_difference[ p ][ y ][ x ] | } | } | 4.6.1. plane_pixel_width "plane_pixel_width[ p ]" is the width in pixels of plane p of the - slice. "plane_pixel_width[ 0 ]" and "plane_pixel_width[ 1 + ( - chroma_planes ? 2 : 0 ) ]" value is "slice_pixel_width". If - "chroma_planes" is set to 1, "plane_pixel_width[ 1 ]" and - "plane_pixel_width[ 2 ]" value is "ceil(slice_pixel_width / - v_chroma_subsample)". + slice. + "plane_pixel_width[ 0 ]" and "plane_pixel_width[ 1 + ( chroma_planes + ? 2 : 0 ) ]" value is "slice_pixel_width". + If "chroma_planes" is set to 1, "plane_pixel_width[ 1 ]" and + "plane_pixel_width[ 2 ]" value is "ceil(slice_pixel_width / (1 << + log2_h_chroma_subsample))". 4.6.2. slice_pixel_width - "slice_pixel_width" is the width in pixels of the slice. Its value - is "floor(( slice_x + slice_width ) * slice_pixel_width / + "slice_pixel_width" is the width in pixels of the slice. + Its value is "floor(( slice_x + slice_width ) * slice_pixel_width / num_h_slices) - slice_pixel_x". 4.6.3. slice_pixel_x - "slice_pixel_x" is the slice horizontal position in pixels. Its - value is "floor(slice_x * frame_pixel_width / num_h_slices)". + "slice_pixel_x" is the slice horizontal position in pixels. + Its value is "floor(slice_x * frame_pixel_width / num_h_slices)". + +4.6.4. sample_difference + + "sample_difference[ p ][ y ][ x ]" is the sample difference for + sample at plane "p", y position "y" and x position "x". Sample value + is computed based on prediction and context described in Section 3.2. 4.7. Slice Footer Note: slice footer is always byte aligned. pseudo-code | type --------------------------------------------------------------|----- SliceFooter( ) { | slice_size | u(24) if (ec) { | error_status | u(8) slice_crc_parity | u(32) } | } | 4.7.1. slice_size - "slice_size" indicates the size of the slice in bytes. Note: this - allows finding the start of slices before previous slices have been - fully decoded. And allows this way parallel decoding as well as - error resilience. + "slice_size" indicates the size of the slice in bytes. + Note: this allows finding the start of slices before previous slices + have been fully decoded. And allows this way parallel decoding as + well as error resilience. 4.7.2. error_status "error_status" specifies the error status. +-------+--------------------------------------+ | value | error status | +-------+--------------------------------------+ | 0 | no error | | 1 | slice contains a correctable error | | 2 | slice contains a uncorrectable error | | Other | reserved for future use | +-------+--------------------------------------+ 4.7.3. slice_crc_parity "slice_crc_parity" 32 bits that are chosen so that the slice as a - whole has a crc remainder of 0. This is equivalent to storing the - crc remainder in the 32-bit parity. The CRC generator polynomial - used is the standard IEEE CRC polynomial (0x104C11DB7) with initial - value 0. + whole has a crc remainder of 0. + This is equivalent to storing the crc remainder in the 32-bit parity. + The CRC generator polynomial used is the standard IEEE CRC polynomial + (0x104C11DB7) with initial value 0. 4.8. Parameters pseudo-code | type --------------------------------------------------------------|----- Parameters( ) { | version | ur if (version >= 3) | micro_version | ur coder_type | ur if (coder_type > 1) | for (i = 1; i < 256; i++) | state_transition_delta[ i ] | sr colorspace_type | ur if (version >= 1) | bits_per_raw_sample | ur chroma_planes | br - log2( h_chroma_subsample ) | ur - log2( v_chroma_subsample ) | ur + log2_h_chroma_subsample | ur + log2_v_chroma_subsample | ur alpha_plane | br if (version >= 3) { | num_h_slices - 1 | ur num_v_slices - 1 | ur quant_table_set_count | ur } | for( i = 0; i < quant_table_set_count; i++ ) | QuantizationTableSet( i ) | if (version >= 3) { | for( i = 0; i < quant_table_set_count; i++ ) { | @@ -1263,218 +1297,236 @@ for( k = 0; k < CONTEXT_SIZE; k++ ) | initial_state_delta[ i ][ j ][ k ] | sr } | ec | ur intra | ur } | } | 4.8.1. version - "version" specifies the version of the bitstream. Each version is - incompatible with others versions: decoders SHOULD reject a file due - to unknown version. Decoders SHOULD reject a file with version <= 1 - && ConfigurationRecordIsPresent == 1. Decoders SHOULD reject a file - with version >= 3 && ConfigurationRecordIsPresent == 0. + "version" specifies the version of the FFV1 bitstream. + Each version is incompatible with others versions: decoders SHOULD + reject a file due to unknown version. + Decoders SHOULD reject a file with version <= 1 && + ConfigurationRecordIsPresent == 1. + Decoders SHOULD reject a file with version >= 3 && + ConfigurationRecordIsPresent == 0. +-------+-------------------------+ | value | version | +-------+-------------------------+ | 0 | FFV1 version 0 | | 1 | FFV1 version 1 | | 2 | reserved* | | 3 | FFV1 version 3 | | Other | reserved for future use | +-------+-------------------------+ * Version 2 was never enabled in the encoder thus version 2 files SHOULD NOT exist, and this document does not describe them to keep the text simpler. 4.8.2. micro_version - "micro_version" specifies the micro-version of the bitstream. After - a version is considered stable (a micro-version value is assigned to - be the first stable variant of a specific version), each new micro- - version after this first stable variant is compatible with the - previous micro-version: decoders SHOULD NOT reject a file due to an - unknown micro-version equal or above the micro-version considered as - stable. + "micro_version" specifies the micro-version of the FFV1 bitstream. + After a version is considered stable (a micro-version value is + assigned to be the first stable variant of a specific version), each + new micro-version after this first stable variant is compatible with + the previous micro-version: decoders SHOULD NOT reject a file due to + an unknown micro-version equal or above the micro-version considered + as stable. Meaning of micro_version for version 3: +-------+-------------------------+ | value | micro_version | +-------+-------------------------+ | 0...3 | reserved* | | 4 | first stable variant | | Other | reserved for future use | +-------+-------------------------+ - * were development versions which may be incompatible with the stable + * development versions which may be incompatible with the stable variants. Meaning of micro_version for version 4 (note: at the time of writing of this specification, version 4 is not considered stable so the first stable version value is to be announced in the future): +---------+-------------------------+ | value | micro_version | +---------+-------------------------+ | 0...TBA | reserved* | | TBA | first stable variant | | Other | reserved for future use | +---------+-------------------------+ - * were development versions which may be incompatible with the stable + * development versions which may be incompatible with the stable variants. 4.8.3. coder_type - "coder_type" specifies the coder used + "coder_type" specifies the coder used. +-------+-------------------------------------------------+ | value | coder used | +-------+-------------------------------------------------+ | 0 | Golomb Rice | | 1 | Range Coder with default state transition table | | 2 | Range Coder with custom state transition table | | Other | reserved for future use | +-------+-------------------------------------------------+ 4.8.4. state_transition_delta "state_transition_delta" specifies the Range coder custom state - transition table. If state_transition_delta is not present in the - bitstream, all Range coder custom state transition table elements are - assumed to be 0. + transition table. + If state_transition_delta is not present in the FFV1 bitstream, all + Range coder custom state transition table elements are assumed to be + 0. 4.8.5. colorspace_type - "colorspace_type" specifies the color space. + "colorspace_type" specifies color space losslessly encoded, Pixel + transformation used by the encoder, as well as interleave method. - +-------+-------------------------+ - | value | color space used | - +-------+-------------------------+ - | 0 | YCbCr | - | 1 | JPEG2000-RCT | - | Other | reserved for future use | - +-------+-------------------------+ + +-------+---------------------+------------------+------------------+ + | value | color space | transformation | interleave | + | | losslessly encoded | | method | + +-------+---------------------+------------------+------------------+ + | 0 | YCbCr | No Pixel | plane then line | + | | | transformation | | + | 1 | RGB | JPEG2000-RCT | line then plane | + | Other | reserved for future | reserved for | reserved for | + | | use | future use | future use | + +-------+---------------------+------------------+------------------+ + + Restrictions: + If "colorspace_type" is 1, "chroma_planes" MUST be 1, + "h_chroma_subsample" MUST be 1, "v_chroma_subsample" MUST be 1. 4.8.6. chroma_planes "chroma_planes" indicates if chroma (color) planes are present. +-------+-------------------------------+ - | value | color space used | + | value | presence | +-------+-------------------------------+ | 0 | chroma planes are not present | | 1 | chroma planes are present | +-------+-------------------------------+ 4.8.7. bits_per_raw_sample - "bits_per_raw_sample" indicates the number of bits for each luma and - chroma sample. Inferred to be 8 if not present. + "bits_per_raw_sample" indicates the number of bits for each sample. + Inferred to be 8 if not present. - +-------+-------------------------------------------------+ - | value | bits for each luma and chroma sample | - +-------+-------------------------------------------------+ + +-------+---------------------------------+ + | value | bits for each sample | + +-------+---------------------------------+ | 0 | reserved* | - | Other | the actual bits for each luma and chroma sample | - +-------+-------------------------------------------------+ + | Other | the actual bits for each sample | + +-------+---------------------------------+ * Encoders MUST NOT store bits_per_raw_sample = 0 Decoders SHOULD accept and interpret bits_per_raw_sample = 0 as 8. -4.8.8. h_chroma_subsample +4.8.8. log2_h_chroma_subsample - "h_chroma_subsample" indicates the subsample factor between luma and - chroma width ("chroma_width = 2^(-log2_h_chroma_subsample) * - luma_width"). + "log2_h_chroma_subsample" indicates the subsample factor, stored in + powers to which the number 2 must be raised, between luma and chroma + width ("chroma_width = 2^(-log2_h_chroma_subsample) * luma_width"). -4.8.9. v_chroma_subsample +4.8.9. log2_v_chroma_subsample - "v_chroma_subsample" indicates the subsample factor between luma and - chroma height ("chroma_height=2^(-log2_v_chroma_subsample) * - luma_height"). + "log2_v_chroma_subsample" indicates the subsample factor, stored in + powers to which the number 2 must be raised, between luma and chroma + height ("chroma_height=2^(-log2_v_chroma_subsample) * luma_height"). 4.8.10. alpha_plane - alpha_plane - indicates if a transparency plane is present. + "alpha_plane" indicates if a transparency plane is present. +-------+-----------------------------------+ - | value | color space used | + | value | presence | +-------+-----------------------------------+ | 0 | transparency plane is not present | | 1 | transparency plane is present | +-------+-----------------------------------+ 4.8.11. num_h_slices "num_h_slices" indicates the number of horizontal elements of the - slice raster. Inferred to be 1 if not present. + slice raster. + Inferred to be 1 if not present. 4.8.12. num_v_slices "num_v_slices" indicates the number of vertical elements of the slice - raster. Inferred to be 1 if not present. + raster. + Inferred to be 1 if not present. 4.8.13. quant_table_set_count "quant_table_set_count" indicates the number of Quantization - Table Sets. Inferred to be 1 if not present. MUST NOT be 0. + Table Sets. + Inferred to be 1 if not present. + MUST NOT be 0. 4.8.14. states_coded "states_coded" indicates if the respective Quantization Table Set has - the initial states coded. Inferred to be 0 if not present. + the initial states coded. + Inferred to be 0 if not present. +-------+-----------------------------------------------------------+ | value | initial states | +-------+-----------------------------------------------------------+ | 0 | initial states are not present and are assumed to be all | | | 128 | | 1 | initial states are present | +-------+-----------------------------------------------------------+ 4.8.15. initial_state_delta - "initial_state_delta" [ i ][ j ][ k ] indicates the initial Range - coder state, it is encoded using k as context index and pred = j ? - initial_states[ i ][j - 1][ k ] : 128 initial_state[ i ][ j ][ k ] = + "initial_state_delta[ i ][ j ][ k ]" indicates the initial Range + coder state, it is encoded using "k" as context index and + + pred = j ? initial_states[ i ][j - 1][ k ] : 128 + + initial_state[ i ][ j ][ k ] = ( pred + initial_state_delta[ i ][ j ][ k ] ) & 255 4.8.16. ec "ec" indicates the error detection/correction type. +-------+--------------------------------------------+ | value | error detection/correction type | +-------+--------------------------------------------+ | 0 | 32-bit CRC on the global header | | 1 | 32-bit CRC per slice and the global header | | Other | reserved for future use | +-------+--------------------------------------------+ 4.8.17. intra - "intra" indicates the relationship between frames. Inferred to be 0 - if not present. + "intra" indicates the relationship between the instances of "Frame". + Inferred to be 0 if not present. +-------+-----------------------------------------------------------+ | value | relationship | +-------+-----------------------------------------------------------+ - | 0 | frames are independent or dependent (keyframes and non | + | 0 | Frames are independent or dependent (keyframes and non | | | keyframes) | - | 1 | frames are independent (keyframes only) | + | 1 | Frames are independent (keyframes only) | | Other | reserved for future use | +-------+-----------------------------------------------------------+ 4.9. Quantization Table Set The Quantization Table Sets are stored by storing the number of equal entries -1 of the first half of the table (represented as "len - 1" in the pseudo-code below) using the method described in Section 3.8.1.2. The second half doesn't need to be stored as it is identical to the first with flipped sign. @@ -1532,45 +1584,45 @@ 5. Restrictions To ensure that fast multithreaded decoding is possible, starting version 3 and if frame_pixel_width * frame_pixel_height is more than 101376, slice_width * slice_height MUST be less or equal to num_h_slices * num_v_slices / 4. Note: 101376 is the frame size in pixels of a 352x288 frame also known as CIF ("Common Intermediate Format") frame size format. - For each frame, each position in the slice raster MUST be filled by - one and only one slice of the frame (no missing slice position, no + For each "Frame", each position in the slice raster MUST be filled by + one and only one slice of the "Frame" (no missing slice position, no slice overlapping). - For each Frame with keyframe value of 0, each slice MUST have the + For each "Frame" with keyframe value of 0, each slice MUST have the same value of slice_x, slice_y, slice_width, slice_height as a slice - in the previous frame, except if reset_contexts is 1. + in the previous "Frame", except if reset_contexts is 1. 6. Security Considerations Like any other codec, (such as [RFC6716]), FFV1 should not be used with insecure ciphers or cipher-modes that are vulnerable to known plaintext attacks. Some of the header bits as well as the padding are easily predictable. Implementations of the FFV1 codec need to take appropriate security considerations into account, as outlined in [RFC4732]. It is extremely important for the decoder to be robust against malicious payloads. Malicious payloads must not cause the decoder to overrun its allocated memory or to take an excessive amount of resources to decode. Although problems in encoders are typically rarer, the same applies to the encoder. Malicious video streams must not cause the encoder to misbehave because this would allow an attacker to attack transcoding gateways. A frequent security problem in image and video - codecs is also to not check for integer overflows in pixel count + codecs is also to not check for integer overflows in Pixel count computations, that is to allocate width * height without considering that the multiplication result may have overflowed the arithmetic types range. The reference implementation [REFIMPL] contains no known buffer overflow or cases where a specially crafted packet or video segment could cause a significant increase in CPU load. The reference implementation [REFIMPL] was validated in the following conditions: @@ -1588,37 +1640,37 @@ inside the [VALGRIND] memory debugger as well as clangs address sanitizer [Address-Sanitizer], which track reads and writes to invalid memory regions as well as the use of uninitialized memory. There were no errors reported on any of the tested conditions. 7. Appendixes 7.1. Decoder implementation suggestions 7.1.1. Multi-threading support and independence of slices - The bitstream is parsable in two ways: in sequential order as + The FFV1 bitstream is parsable in two ways: in sequential order as described in this document or with the pre-analysis of the footer of each slice. Each slice footer contains a slice_size field so the boundary of each slice is computable without having to parse the slice content. That allows multi-threading as well as independence of slice content (a bitstream error in a slice header or slice content has no impact on the decoding of the other slices). After having checked keyframe field, a decoder SHOULD parse slice_size fields, from slice_size of the last slice at the end of - the frame up to slice_size of the first slice at the beginning of the - frame, before parsing slices, in order to have slices boundaries. A - decoder MAY fallback on sequential order e.g. in case of corrupted - frame (frame size unknown, slice_size of slices not coherent...) or - if there is no possibility of seek into the stream. + the "Frame" up to slice_size of the first slice at the beginning of + the "Frame", before parsing slices, in order to have slices + boundaries. A decoder MAY fallback on sequential order e.g. in case + of a corrupted "Frame" (frame size unknown, slice_size of slices not + coherent...) or if there is no possibility of seek into the stream. - Architecture overview of slices in a frame: + Architecture overview of slices in a "Frame": +-----------------------------------------------------------------+ | first slice header | | first slice content | | first slice footer | | --------------------------------------------------------------- | | second slice header | | second slice content | | second slice footer | | --------------------------------------------------------------- | @@ -1646,21 +1698,21 @@ "Information technology -- JPEG 2000 image coding system: Core coding system", October 2016. [ISO.9899.1990] International Organization for Standardization, "Programming languages - C", ISO Standard 9899, 1990. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, - . + . 10.2. Informative References [Address-Sanitizer] The Clang Team, "ASAN AddressSanitizer website", undated, . [AVI] Microsoft, "AVI RIFF File Reference", undated, . @@ -1712,32 +1764,32 @@ Institution of Electronic and Radio Engineers International Conference on Video and Data Recording , July 1979. [REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the FFV1 codec in FFmpeg", undated, . [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet Denial-of-Service Considerations", RFC 4732, DOI 10.17487/RFC4732, December 2006, - . + . [RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716, - September 2012, . + September 2012, . [VALGRIND] Valgrind Developers, "Valgrind website", undated, . - [YCbCr] Wikipedia, "YCbCr", undated, . + [YCbCr] Wikipedia, "YCbCr", undated, + . Authors' Addresses Michael Niedermayer Email: michael@niedermayer.cc Dave Rice Email: dave@dericed.com