[FFmpeg-devel] [PATCH] Make decoding alpha option for some codecs.

[Michael Niedermayer]

On Tue, Sep 17, 2013 at 09:31:07PM +0200, Reimar Döffinger wrote:
> For codecs where decoding of a whole plane can simply
> be skipped, we should offer applications to not decode
> alpha for better performance.
> It also means applications do not need to implement support
> (even if it is rather simple) for YUVA formats in order to be
> able to play these files.
> Unfortunately a good way to test this via FFmpeg only is missing,
> suggestions welcome.
> 
> Signed-off-by: Reimar Döffinger <Reimar.Doeffinger at gmx.de>
> ---
>  libavcodec/ffv1dec.c        | 15 ++++++++++++---
>  libavcodec/proresdec2.c     |  8 +++++++-
>  libavcodec/proresdec_lgpl.c | 14 +++++++++++++-
>  libavcodec/vp56.c           | 12 ++++++++----
>  4 files changed, 40 insertions(+), 9 deletions(-)
> 

> diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c
> index 5455660..75e26bc 100644
> --- a/libavcodec/ffv1dec.c
> +++ b/libavcodec/ffv1dec.c
> @@ -659,14 +659,23 @@ static int read_header(FFV1Context *f)
>                  return AVERROR(ENOSYS);
>              }
>          } else if (f->avctx->bits_per_raw_sample <= 8 && f->transparency) {
> +            static const enum AVPixelFormat alpha_fmts[][3] = {
> +                {AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUV444P, AV_PIX_FMT_NONE},
> +                {AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_NONE},
> +                {AV_PIX_FMT_YUVA420P, AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE}
> +            };
>              switch(16*f->chroma_h_shift + f->chroma_v_shift) {
> -            case 0x00: f->avctx->pix_fmt = AV_PIX_FMT_YUVA444P; break;
> -            case 0x10: f->avctx->pix_fmt = AV_PIX_FMT_YUVA422P; break;
> -            case 0x11: f->avctx->pix_fmt = AV_PIX_FMT_YUVA420P; break;
> +            case 0x00: f->avctx->pix_fmt = f->avctx->get_format(f->avctx, alpha_fmts[0]); break;
> +            case 0x10: f->avctx->pix_fmt = f->avctx->get_format(f->avctx, alpha_fmts[1]); break;
> +            case 0x11: f->avctx->pix_fmt = f->avctx->get_format(f->avctx, alpha_fmts[2]); break;
>              default:
>                  av_log(f->avctx, AV_LOG_ERROR, "format not supported\n");
>                  return AVERROR(ENOSYS);
>              }
> +            if (f->avctx->pix_fmt != AV_PIX_FMT_YUVA444P &&
> +                f->avctx->pix_fmt != AV_PIX_FMT_YUVA422P &&
> +                f->avctx->pix_fmt != AV_PIX_FMT_YUVA420P)
> +                f->transparency = 0;
>          } else if (f->avctx->bits_per_raw_sample == 9) {
>              f->packed_at_lsb = 1;
>              switch(16 * f->chroma_h_shift + f->chroma_v_shift) {

LGTM if tested

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

If a bugfix only changes things apparently unrelated to the bug with no
further explanation, that is a good sign that the bugfix is wrong.
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