[FFmpeg-devel] [PATCH] avcodec/ffv1: Support for RGBA64 and GBRAP16

[Michael Niedermayer]

On Thu, Feb 01, 2018 at 01:43:00PM +0100, Jerome Martinez wrote:
> Add support for 16-bit/component RGB with Alpha encoding and decoding in
> FFV1, both RGBA64 and GBRAP16 for encoding, GBRAP16 for decoding.
> 
> Resulting bitstream was tested about lossless encoding/decoding by the
> compression from DPX to FFV1 then decompression from FFV1 to DPX, see
> commands below (resulting framemd5 hashes are all same).
> Resulting bitstream is decodable by another decoder (with same resulting
> framemd5 hash).
> Resulting bitstream passed through a conformance checker compared to current
> FFV1 specification IETF draft.
> 
> About the patch:
> - some modified lines are not used (the ones not used when f->use32bit is
> 1), but it makes the code more coherent (especially because decode_rgb_frame
> signature is same for both 16-bit and 32-bit version) and prepares the
> support of RGBA with 10/12/14 bits/component.
> - GBRAP16 was chosen for decoding because GBRP16 is already used when no
> alpha, and the code is more prepared for planar pix_fmt when bit depth is
> >8.
> - "s->transparency = desc->nb_components == 4 || desc->nb_components == 2;"
> is a copy of a line a bit above about the detection of transparency, I
> preferred to reuse it as is even if "YA" 16-bit/component is not (yet)
> supported.
> 
> FFmpeg commands used for tests:
> ./ffmpeg -i in.dpx -c:v ffv1 out.mkv
> ./ffmpeg -i in.dpx -pix_fmt gbrap16 -strict -2 -c:v ffv1 out2.mkv
> ./ffmpeg -i out.mkv out.dpx
> 
> ./ffmpeg -i in.dpx -f framemd5 in.dpx.framemd5
> ./ffmpeg -i out.mkv -pix_fmt rgba64be -f framemd5 out.mkv.framemd5
> ./ffmpeg -i out2.mkv -pix_fmt rgba64be -f framemd5 out2.mkv.framemd5
> ./ffmpeg -i out.dpx -f framemd5 out.dpx.framemd5
> 
> Test file used (renamed to in.dpx):
> https://mediaarea.net/temp/uncropped_DPX_4K_16bit_Overscan15pros.dpx

I would prefer if the algorithm would be tuned to 16bit data before
adding more formats to the encoder which require all decoders to support
them.

Dont you agree that this would be the better strategy ?

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

What does censorship reveal? It reveals fear. -- Julian Assange
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