[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
> 
> Jérôme
> 

[...]
> diff --git a/libavcodec/ffv1enc_template.c b/libavcodec/ffv1enc_template.c
> index b7eea0dd70..2763082540 100644
> --- a/libavcodec/ffv1enc_template.c
> +++ b/libavcodec/ffv1enc_template.c
> @@ -122,8 +122,8 @@ static av_always_inline int RENAME(encode_line)(FFV1Context *s, int w,
>      return 0;
>  }
>  
> -static int RENAME(encode_rgb_frame)(FFV1Context *s, const uint8_t *src[3],
> -                                    int w, int h, const int stride[3])
> +static int RENAME(encode_rgb_frame)(FFV1Context *s, const uint8_t *src[4],
> +                                    int w, int h, const int stride[4])
>  {
>      int x, y, p, i;
>      const int ring_size = s->context_model ? 3 : 2;
> @@ -152,14 +152,18 @@ static int RENAME(encode_rgb_frame)(FFV1Context *s, const uint8_t *src[3],
>                  r = (v >> 16) & 0xFF;
>                  a =  v >> 24;
>              } else if (packed) {
> -                const uint16_t *p = ((const uint16_t*)(src[0] + x*6 + stride[0]*y));
> +                const uint16_t *p = ((const uint16_t*)(src[0] + x*(3 + s->transparency)*2 + stride[0]*y));
>                  r = p[0];
>                  g = p[1];
>                  b = p[2];

> +                if (s->transparency)

transparency should possibly be moved into a local variable


> +                  a = p[3];
>              } else if (sizeof(TYPE) == 4) {
>                  g = *((const uint16_t *)(src[0] + x*2 + stride[0]*y));
>                  b = *((const uint16_t *)(src[1] + x*2 + stride[1]*y));
>                  r = *((const uint16_t *)(src[2] + x*2 + stride[2]*y));
> +                if (s->transparency)
> +                    a = *((const uint16_t *)(src[3] + x*2 + stride[2]*y));
                                                               ^^^^^^^^^
this looks wrong


also what speed effect do thes changes to the inner loop have ?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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