--- 1/draft-ietf-cellar-ffv1-06.txt 2019-02-06 07:13:30.250402940 -0800 +++ 2/draft-ietf-cellar-ffv1-07.txt 2019-02-06 07:13:30.346405228 -0800 @@ -1,20 +1,20 @@ cellar M. Niedermayer Internet-Draft Intended status: Informational D. Rice -Expires: April 21, 2019 +Expires: August 10, 2019 J. Martinez - October 18, 2018 + February 6, 2019 FFV1 Video Coding Format Version 0, 1, and 3 - draft-ietf-cellar-ffv1-06 + draft-ietf-cellar-ffv1-07 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 @@ -25,144 +25,143 @@ 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 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 April 21, 2019. + This Internet-Draft will expire on August 10, 2019. Copyright Notice - Copyright (c) 2018 IETF Trust and the persons identified as the + Copyright (c) 2019 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 (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 . . . . . . . . . . . . . . . . . . . . . . . 5 - 2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5 + 2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 6 2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 6 2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 6 2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 6 2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 7 2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 7 2.2.6. Order of Operation Precedence . . . . . . . . . . . . 8 2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 8 2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 8 3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 10 3.4. Context . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.5. Quantization Table Sets . . . . . . . . . . . . . . . . . 11 3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 12 3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 12 3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 12 3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.8. Coding of the Sample Difference . . . . . . . . . . . . . 14 - 3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 14 - 3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 18 - 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 20 - 4.1. Parameters . . . . . . . . . . . . . . . . . . . . . . . 21 - 4.1.1. version . . . . . . . . . . . . . . . . . . . . . . . 22 - 4.1.2. micro_version . . . . . . . . . . . . . . . . . . . . 23 - 4.1.3. coder_type . . . . . . . . . . . . . . . . . . . . . 23 - 4.1.4. state_transition_delta . . . . . . . . . . . . . . . 24 - 4.1.5. colorspace_type . . . . . . . . . . . . . . . . . . . 24 - 4.1.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 24 - 4.1.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 24 - 4.1.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 25 - 4.1.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 25 - 4.1.10. alpha_plane . . . . . . . . . . . . . . . . . . . . . 25 - 4.1.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 25 - 4.1.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 25 - 4.1.13. quant_table_set_count . . . . . . . . . . . . . . . . 26 - 4.1.14. states_coded . . . . . . . . . . . . . . . . . . . . 26 - 4.1.15. initial_state_delta . . . . . . . . . . . . . . . . . 26 - 4.1.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 26 - 4.1.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 26 - 4.2. Configuration Record . . . . . . . . . . . . . . . . . . 27 - 4.2.1. reserved_for_future_use . . . . . . . . . . . . . . . 27 - 4.2.2. configuration_record_crc_parity . . . . . . . . . . . 27 - 4.2.3. Mapping FFV1 into Containers . . . . . . . . . . . . 28 - 4.3. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 29 - 4.4. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 29 - 4.5. Slice Header . . . . . . . . . . . . . . . . . . . . . . 30 - 4.5.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 31 - 4.5.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 31 - 4.5.3. slice_width . . . . . . . . . . . . . . . . . . . . . 31 - 4.5.4. slice_height . . . . . . . . . . . . . . . . . . . . 31 - 4.5.5. quant_table_set_index_count . . . . . . . . . . . . . 31 - 4.5.6. quant_table_set_index . . . . . . . . . . . . . . . . 31 - 4.5.7. picture_structure . . . . . . . . . . . . . . . . . . 32 - 4.5.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 32 - 4.5.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 32 - 4.6. Slice Content . . . . . . . . . . . . . . . . . . . . . . 32 - 4.6.1. primary_color_count . . . . . . . . . . . . . . . . . 33 - 4.6.2. plane_pixel_height . . . . . . . . . . . . . . . . . 33 - 4.6.3. slice_pixel_height . . . . . . . . . . . . . . . . . 33 - 4.6.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 33 - 4.7. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 33 - 4.7.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 34 - 4.7.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 34 - 4.7.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 34 - 4.7.4. sample_difference . . . . . . . . . . . . . . . . . . 34 - 4.8. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 34 - 4.8.1. slice_size . . . . . . . . . . . . . . . . . . . . . 35 - 4.8.2. error_status . . . . . . . . . . . . . . . . . . . . 35 - 4.8.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 35 - 4.9. Quantization Table Set . . . . . . . . . . . . . . . . . 35 - 4.9.1. quant_tables . . . . . . . . . . . . . . . . . . . . 36 - 4.9.2. context_count . . . . . . . . . . . . . . . . . . . . 37 - 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 37 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 37 - 7. Media Type Definition . . . . . . . . . . . . . . . . . . . . 38 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40 - 9. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . 40 - 9.1. Decoder implementation suggestions . . . . . . . . . . . 40 - 9.1.1. Multi-threading Support and Independence of Slices . 40 - 10. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 40 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 40 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 40 - 11.2. Informative References . . . . . . . . . . . . . . . . . 41 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43 + 3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 15 + 3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 19 + 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 24 + 4.1. Parameters . . . . . . . . . . . . . . . . . . . . . . . 24 + 4.1.1. version . . . . . . . . . . . . . . . . . . . . . . . 25 + 4.1.2. micro_version . . . . . . . . . . . . . . . . . . . . 26 + 4.1.3. coder_type . . . . . . . . . . . . . . . . . . . . . 26 + 4.1.4. state_transition_delta . . . . . . . . . . . . . . . 27 + 4.1.5. colorspace_type . . . . . . . . . . . . . . . . . . . 27 + 4.1.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 27 + 4.1.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 28 + 4.1.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 28 + 4.1.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 28 + 4.1.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 28 + 4.1.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 28 + 4.1.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 29 + 4.1.13. quant_table_set_count . . . . . . . . . . . . . . . . 29 + 4.1.14. states_coded . . . . . . . . . . . . . . . . . . . . 29 + 4.1.15. initial_state_delta . . . . . . . . . . . . . . . . . 29 + 4.1.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 29 + 4.1.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 30 + 4.2. Configuration Record . . . . . . . . . . . . . . . . . . 30 + 4.2.1. reserved_for_future_use . . . . . . . . . . . . . . . 30 + 4.2.2. configuration_record_crc_parity . . . . . . . . . . . 30 + 4.2.3. Mapping FFV1 into Containers . . . . . . . . . . . . 31 + 4.3. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 32 + 4.4. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 32 + 4.5. Slice Header . . . . . . . . . . . . . . . . . . . . . . 33 + 4.5.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 34 + 4.5.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 34 + 4.5.3. slice_width . . . . . . . . . . . . . . . . . . . . . 34 + 4.5.4. slice_height . . . . . . . . . . . . . . . . . . . . 34 + 4.5.5. quant_table_set_index_count . . . . . . . . . . . . . 34 + 4.5.6. quant_table_set_index . . . . . . . . . . . . . . . . 34 + 4.5.7. picture_structure . . . . . . . . . . . . . . . . . . 35 + 4.5.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 35 + 4.5.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 35 + 4.6. Slice Content . . . . . . . . . . . . . . . . . . . . . . 35 + 4.6.1. primary_color_count . . . . . . . . . . . . . . . . . 36 + 4.6.2. plane_pixel_height . . . . . . . . . . . . . . . . . 36 + 4.6.3. slice_pixel_height . . . . . . . . . . . . . . . . . 36 + 4.6.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 36 + 4.7. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 36 + 4.7.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 37 + 4.7.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 37 + 4.7.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 37 + 4.7.4. sample_difference . . . . . . . . . . . . . . . . . . 37 + 4.8. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 37 + 4.8.1. slice_size . . . . . . . . . . . . . . . . . . . . . 38 + 4.8.2. error_status . . . . . . . . . . . . . . . . . . . . 38 + 4.8.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 38 + 4.9. Quantization Table Set . . . . . . . . . . . . . . . . . 38 + 4.9.1. quant_tables . . . . . . . . . . . . . . . . . . . . 39 + 4.9.2. context_count . . . . . . . . . . . . . . . . . . . . 40 + 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 40 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 40 + 7. Media Type Definition . . . . . . . . . . . . . . . . . . . . 41 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 43 + 9. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . 43 + 9.1. Decoder implementation suggestions . . . . . . . . . . . 43 + 9.1.1. Multi-threading Support and Independence of Slices . 43 + 10. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 43 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 43 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 43 + 11.2. Informative References . . . . . . . . . . . . . . . . . 44 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46 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 encodings. - This document defines a version 0, 1, and 3 of FFV1. The - distinctions of the versions are provided throughout the document, - but in summary: + This document defines version 0, 1 and 3 of FFV1. The distinctions + of the versions are provided throughout the document, but in summary: o Version 0 of FFV1 was the original implementation of FFV1 and has been in non-experimental use since April 14, 2006 [FFV1_V0]. o Version 1 of FFV1 adds support of more video bit depths and has been in use since April 24, 2009 [FFV1_V1]. o Version 2 of FFV1 only existed in experimental form and is not described by this document, but is available as a LyX file at > b" means arithmetic right shift of two's complement integer representation of a by b binary digits. "a << b" means arithmetic left shift of two's complement integer representation of a by b binary digits. @@ -328,59 +331,65 @@ 2.2.6. Order of Operation Precedence When order of precedence is not indicated explicitly by use of parentheses, operations are evaluated in the following order (from top to bottom, operations of same precedence being evaluated from left to right). This order of operations is based on the order of operations used in Standard C. a++, a-- !a, -a + a ^ b a * b, a / b, a % b a + b, a - b a << b, a >> b a < b, a <= b, a > b, a >= b a == b, a != b a & b a | b a && b a || b a ? b : c a = b, a += b, a -= b, a *= b 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 "Configuration Record" or "Frame". FFV1 + octets of a particular FFV1 "Configuration Record" or "Frame". FFV1 relies on its "Container" to store the "NumBytes" values, see Section 4.2.3. 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 pointer in that "Configuration Record" or "Frame". It is computed from the "NumBytes" value multiplied by 8 minus the count of bits of that "Configuration Record" or "Frame" already read by the bitstream parser. -2.2.9.2. byte_aligned +2.2.9.2. remaining_symbols_in_syntax + + "remaining_symbols_in_syntax( )" is true as long as the RangeCoder + has not consumed all the given input bytes. + +2.2.9.3. 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 +2.2.9.4. 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. Sample Coding For each "Slice" (as described in Section 4.4) of a "Frame", the "Planes", "Lines", and "Samples" are coded in an order determined by the "Color Space" (see Section 3.7). Each "Sample" is predicted by @@ -517,109 +526,118 @@ 3.6. Quantization Table Set Indexes For each "Plane" of each slice, a Quantization Table Set is selected from an index: 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 || + o For extra "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 FFV1 bitstreams in the wild. 3.7. Color spaces - FFV1 supports two color spaces: YCbCr and RGB. Both color spaces - allow an optional Alpha "Plane" that can be used to code transparency - data. + FFV1 supports several color spaces. The count of allowed coded + planes and the meaning of the extra "Plane" are determined by the + selected color space. The FFV1 bitstream interleaves data in an order determined by the color space. In YCbCr for each "Plane", each "Line" is coded from top to bottom and for each "Line", each "Sample" is coded from left to right. In JPEG2000-RCT for each "Line" from top to bottom, each "Plane" is coded and for each "Plane", each "Sample" is encoded from left to right. 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 MUST use one of the following arrangements: + This color space allows 1 to 4 "Planes". + 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 optional transparency "Plane" can be used to code transparency + data. + + An FFV1 "Frame" using YCbCr MUST use one of the following + arrangements: o Y - o Y, Alpha + + o Y, Transparency o Y, Cb, Cr - o Y, Cb, Cr, Alpha + o Y, Cb, Cr, Transparency 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. + used then they MUST be coded after the Y "Plane". If a transparency + "Plane" is used, then it MUST be coded last. 3.7.2. RGB + This color space allows 3 or 4 "Planes". + An optional transparency "Plane" can be used to code transparency + data. + JPEG2000-RCT is a Reversible Color Transform that codes RGB (red, green, blue) "Planes" losslessly in a modified YCbCr color space [ISO.15444-1.2016]. 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 JPEG2000-RCT conversion: if bits_per_raw_sample is - between 9 and 15 inclusive and alpha_plane is 0, the following + between 9 and 15 inclusive and extra_plane is 0, 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 and alpha_plane is 0, GBR "Planes" were used as BGR + inclusive and extra_plane is 0, GBR "Planes" were used as BGR "Planes" during both encoding 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. When FFV1 uses the JPEG2000-RCT, the horizontal "Lines" are interleaved to improve caching efficiency since it is most likely that the JPEG2000-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. + and then if used transparency. 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] | @@ -650,22 +668,22 @@ from H.264 as defined in [ISO.14496-10.2014] but due to the uncertain patent/royalty situation, as well as its slightly worse performance, CABAC was replaced by a Range coder based on an algorithm defined by G. Nigel and N. Martin in 1979 [range-coding]. 3.8.1.1. Range Binary Values To encode binary digits efficiently a Range coder is used. "C_{i}" is the i-th Context. "B_{i}" is the i-th byte of the bytestream. "b_{i}" is the i-th Range coded binary value, "S_{0,i}" is the i-th - initial state, which is 128. The length of the bytestream encoding n - binary symbols is "j_{n}" bytes. + initial state. The length of the bytestream encoding n binary + symbols is "j_{n}" bytes. r_{i} = floor( ( R_{i} * S_{i,C_{i}} ) / 2^8 ) S_{i+1,C_{i}} = zero_state_{S_{i,C_{i}}} XOR l_i = L_i XOR t_i = R_i - r_i <== b_i = 0 <==> L_i < R_i - r_i S_{i+1,C_{i}} = one_state_{S_{i,C_{i}}} XOR @@ -682,34 +700,71 @@ t_{i} < 2^8 R_{i+1} = t_{i} XOR L_{i+1} = l_{i} XOR j_{i+1} = j_{i} <== t_{i} >= 2^8 R_{0} = 65280 L_{0} = 2^8 * B_{0} + B_{1} - j_{0} = 2 +3.8.1.1.1. Termination + + The range coder can be used in 3 modes. + + o In "Open mode" when decoding, every symbol the reader attempts to + read is available. In this mode arbitrary data can have been + appended without affecting the range coder output. This mode is + not used in FFV1. + + o In "Closed mode" the length in bytes of the bytestream is provided + to the range decoder. Bytes beyond the length are read as 0 by + the range decoder. This is generally 1 byte shorter than the open + mode. + + o In "Sentinel mode" the exact length in bytes is not known and thus + the range decoder MAY read into the data that follows the range + coded bytestream by one byte. In "Sentinel mode", the end of the + range coded bytestream is a binary symbol with state 129, which + value SHALL be discarded. After reading this symbol, the range + decoder will have read one byte beyond the end of the range coded + bytestream. This way the byte position of the end can be + determined. Bytestreams written in "Sentinel mode" can be read in + "Closed mode" if the length can be determined, in this case the + last (sentinel) symbol will be read non-corrupted and be of value + 0. + + Above describes the range decoding, encoding is defined as any + process which produces a decodable bytestream. + + There are 3 places where range coder termination is needed in FFV1. + First is in the "Configuration Record", in this case the size of the + range coded bytestream is known and handled as "Closed mode". Second + is the switch from the "Slice Header" which is range coded to Golomb + coded slices as "Sentinel mode". Third is the end of range coded + Slices which need to terminate before the CRC at their end. This can + be handled as "Sentinel mode" or as "Closed mode" if the CRC position + has been determined. + 3.8.1.2. Range Non Binary Values To encode scalar integers, it would be possible to encode each bit separately and use the past bits as context. However that would mean 255 contexts per 8-bit symbol that is not only a waste of memory but also requires more past data to reach a reasonably good estimate of the probabilities. Alternatively assuming a Laplacian distribution and only dealing with its variance and mean (as in Huffman coding) would also be possible, however, for maximum flexibility and simplicity, the chosen method uses a single symbol to encode if a - number is 0 and if not encodes the number using its exponent, + number is 0, and if not, encodes the number using its exponent, mantissa and sign. The exact contexts used are best described by the following code, followed by some comments. pseudo-code | type --------------------------------------------------------------|----- void put_symbol(RangeCoder *c, uint8_t *state, int v, int \ | is_signed) { | int i; | put_rac(c, state+0, !v); | if (v) { | @@ -810,66 +865,86 @@ 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. Golomb Rice Mode + 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. Signed Golomb Rice Codes + This coding mode uses Golomb Rice codes. The VLC is split into 2 parts, the prefix stores the most significant bits and 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. + ESC case. + + pseudo-code | type + --------------------------------------------------------------|----- + int get_ur_golomb(k) { | + for (prefix = 0; prefix < 12; prefix++) { | + if ( get_bits(1) ) | + return get_bits(k) + (prefix << k) | + } | + return get_bits(bits) + 11 | + } | + | + int get_sr_golomb(k) { | + v = get_ur_golomb(k); | + if (v & 1) return - (v >> 1) - 1; | + else return (v >> 1); | + } + +3.8.2.1.1. Prefix -3.8.2.1. Prefix +----------------+-------+ | bits | value | +----------------+-------+ | 1 | 0 | | 01 | 1 | | ... | ... | | 0000 0000 0001 | 11 | | 0000 0000 0000 | ESC | +----------------+-------+ -3.8.2.2. Suffix +3.8.2.1.2. Suffix +-------+-----------------------------------------------------------+ | non | the k least significant bits MSB first | | ESC | | | ESC | the value - 11, in MSB first order, ESC may only be used | | | if the value cannot be coded as non ESC | +-------+-----------------------------------------------------------+ -3.8.2.3. Examples - +3.8.2.1.3. Examples +-----+-------------------------+-------+ | k | bits | value | +-----+-------------------------+-------+ | 0 | "1" | 0 | | 0 | "001" | 2 | | 2 | "1 00" | 0 | | 2 | "1 10" | 2 | | 2 | "01 01" | 5 | | any | "000000000000 10000000" | 139 | +-----+-------------------------+-------+ -3.8.2.4. Run Mode +3.8.2.2. Run Mode Run mode is entered when the context is 0 and left as soon as a non-0 difference is found. The level is identical to the predicted one. The run and the first different level are coded. -3.8.2.5. Run Length Coding +3.8.2.2.1. Run Length Coding The run value is encoded in 2 parts, the prefix part stores the more significant part of the run as well as adjusting the run_index that determines the number of bits in the less significant part of the run. The 2nd part of the value stores the less significant part of the run as it is. The run_index is reset for each "Plane" and slice to 0. pseudo-code | type --------------------------------------------------------------|----- @@ -893,33 +968,87 @@ else | run_count = 0; | if (run_index) | run_index--; | run_mode = 2; | } | } | The log2_run function is also used within [ISO.14495-1.1999]. -3.8.2.6. Level Coding +3.8.2.2.2. Level Coding Level coding is identical to the normal difference coding with the exception that the 0 value is removed as it cannot occur: - if (diff>0) diff--; - encode(diff); + diff = get_vlc_symbol(context_state); + if (diff >= 0) + diff++; Note, this is different from JPEG-LS, which doesn't use prediction in run mode and uses a different encoding and context model for the last difference On a small set of test "Samples" the use of prediction slightly improved the compression rate. +3.8.2.3. Scalar Mode + + Each difference is coded with the per context mean prediction removed + and a per context value for k. + + get_vlc_symbol(state) { + i = state->count; + k = 0; + while (i < state->error_sum) { + k++; + i += i; + } + + v = get_sr_golomb(k); + + if (2 * state->drift < -state->count) + v = - 1 - v; + + ret = sign_extend(v + state->bias, bits); + + state->error_sum += abs(v); + state->drift += v; + + if (state->count == 128) { + state->count >>= 1; + state->drift >>= 1; + state->error_sum >>= 1; + } + state->count++; + if (state->drift <= -state->count) { + state->bias = max(state->bias - 1, -128); + + state->drift = max(state->drift + state->count, + -state->count + 1); + } else if (state->drift > 0) { + state->bias = min(state->bias + 1, 127); + + state->drift = min(state->drift - state->count, 0); + } + + return ret; + } + +3.8.2.4. Initial Values for the VLC context state + + At keyframes all coder state variables are set to their initial + state. + + drift = 0; + error_sum = 4; + bias = 0; + count = 1; + 4. Bitstream An FFV1 bitstream is composed of a series of 1 or more "Frames" and (when required) a "Configuration Record". Within the following sub-sections, pseudo-code is used to explain the structure of each FFV1 bitstream component, as described in Section 2.2.1. The following table lists symbols used to annotate that pseudo-code in order to define the storage of the data referenced in that line of pseudo-code. @@ -970,21 +1099,21 @@ 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 - alpha_plane | br + extra_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++ ) { | states_coded | br @@ -994,22 +1123,22 @@ initial_state_delta[ i ][ j ][ k ] | sr } | ec | ur intra | ur } | } | 4.1.1. version "version" specifies the version of the FFV1 bitstream. - Each version is incompatible with others versions: decoders SHOULD - reject a file due to unknown version. + Each version is incompatible with other versions: decoders SHOULD + reject a file due to an 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 | @@ -1060,35 +1189,38 @@ 4.1.4. state_transition_delta "state_transition_delta" specifies the Range coder custom state 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. 4.1.5. colorspace_type - "colorspace_type" specifies the color space losslessly encoded, the - Pixel transformation used by the encoder, as well as interleave - method. + "colorspace_type" specifies the color space encoded, the pixel + transformation used by the encoder, the extra plane content, as well + as interleave method. - +-------+---------------------+------------------+------------------+ - | value | color space | transformation | interleave | - | | losslessly encoded | | method | - +-------+---------------------+------------------+------------------+ - | 0 | YCbCr | No Pixel | "Plane" then | - | | | transformation | "Line" | - | 1 | RGB | JPEG2000-RCT | "Line" then | - | | | | "Plane" | - | Other | reserved for future | reserved for | reserved for | - | | use | future use | future use | - +-------+---------------------+------------------+------------------+ + +-------+-----------+----------------+---------------+--------------+ + | value | color | pixel | extra plane | interleave | + | | space | transformation | content | method | + | | encoded | | | | + +-------+-----------+----------------+---------------+--------------+ + | 0 | YCbCr | None | Transparency | "Plane" then | + | | | | | "Line" | + | 1 | RGB | JPEG2000-RCT | Transparency | "Line" then | + | | | | | "Plane" | + | Other | reserved | reserved for | reserved for | reserved for | + | | for | future use | future use | future use | + | | future | | | | + | | use | | | | + +-------+-----------+----------------+---------------+--------------+ Restrictions: If "colorspace_type" is 1, then "chroma_planes" MUST be 1, "log2_h_chroma_subsample" MUST be 0, and "log2_v_chroma_subsample" MUST be 0. 4.1.6. chroma_planes "chroma_planes" indicates if chroma (color) "Planes" are present. @@ -1119,30 +1251,30 @@ "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"). 4.1.9. log2_v_chroma_subsample "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"). -4.1.10. alpha_plane +4.1.10. extra_plane - "alpha_plane" indicates if a transparency "Plane" is present. + "extra_plane" indicates if an extra "Plane" is present. - +-------+-------------------------------------+ + +-------+------------------------------+ | value | presence | - +-------+-------------------------------------+ - | 0 | transparency "Plane" is not present | - | 1 | transparency "Plane" is present | - +-------+-------------------------------------+ + +-------+------------------------------+ + | 0 | extra "Plane" is not present | + | 1 | extra "Plane" is present | + +-------+------------------------------+ 4.1.11. num_h_slices "num_h_slices" indicates the number of horizontal elements of the slice raster. Inferred to be 1 if not present. 4.1.12. num_v_slices "num_v_slices" indicates the number of vertical elements of the slice @@ -1212,22 +1344,22 @@ 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) + while( remaining_symbols_in_syntax( NumBytes - 4 ) ) | + reserved_for_future_use | br/ur/sr configuration_record_crc_parity | u(32) } | 4.2.1. 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 @@ -1415,21 +1547,21 @@ 4.5.4. slice_height "slice_height" indicates the height on the slice raster formed by num_v_slices. Inferred to be 1 if not present. 4.5.5. quant_table_set_index_count "quant_table_set_index_count" is defined as "1 + ( ( chroma_planes || - version \<= 3 ) ? 1 : 0 ) + ( alpha_plane ? 1 : 0 )". + version \<= 3 ) ? 1 : 0 ) + ( extra_plane ? 1 : 0 )". 4.5.6. 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. 4.5.7. picture_structure @@ -1483,21 +1615,21 @@ } else if (colorspace_type == 1) { | for( y = 0; y < slice_pixel_height; y++ ) | for( p = 0; p < primary_color_count; p++ ) | Line( p, y ) | } | } | 4.6.1. primary_color_count "primary_color_count" is defined as "1 + ( chroma_planes ? 2 : 0 ) + - ( alpha_plane ? 1 : 0 )". + ( extra_plane ? 1 : 0 )". 4.6.2. 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 "plane_pixel_height[ 2 ]" value is "ceil(slice_pixel_height / log2_v_chroma_subsample)". @@ -1696,21 +1828,23 @@ 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 computations, that is to allocate width * height without considering that the multiplication result may have overflowed the arithmetic - types range. + types range. The range coder could, if implemented naively, read one + byte over the end. The implementation must ensure that no read + outside allocated and initialized memory occurs. 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: o Sending the decoder valid packets generated by the reference encoder and verifying that the decoder's output matches the @@ -1759,21 +1893,21 @@ bits_per_raw_sample: The version of the FFV1 encoding as defined by Section 4.1.7. max-slices: The value of max-slices is an integer indicating the maximum count of slices with a frames of the FFV1 encoding. Encoding considerations: This media type is defined for encapsulation in several audiovisual container formats and contains binary data; see Section 4.2.3. This - media type is framed binary data Section 4.8 of [RFC4288]. + media type is framed binary data Section 4.8 of [RFC6838]. Security considerations: See Section 6 of this document. Interoperability considerations: None. Published specification: [I-D.ietf-cellar-ffv1] and RFC XXXX. @@ -1834,40 +1968,36 @@ See 11. References 11.1. Normative References [I-D.ietf-cellar-ffv1] Niedermayer, M., Rice, D., and J. Martinez, "FFV1 Video Coding Format Version 0, 1, and 3", draft-ietf-cellar- - ffv1-05 (work in progress), September 2018. + ffv1-06 (work in progress), October 2018. [ISO.15444-1.2016] International Organization for Standardization, "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, . - [RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and - Registration Procedures", RFC 4288, DOI 10.17487/RFC4288, - December 2005, . - [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet Denial-of-Service Considerations", RFC 4732, DOI 10.17487/RFC4732, December 2006, . [RFC4855] Casner, S., "Media Type Registration of RTP Payload Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007, . [RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the