[FFmpeg-devel] [PATCH 3/3] avcodec/nvenc: Declare support for P016

[Timo Rothenpieler]

On 02.03.2018 05:26, Philip Langdale wrote:
> nvenc doesn't support P016, but we have two problems today:
> 
> 1) We declare support for YUV444P16 which nvenc also doesn't support.
>    We do this because it's the only pix_fmt we have that can
>    approximate nvenc's internal format that is YUV444P10 with data in
>    MSBs instead of LSBs. Because the declared format is a 16bit one,
>    it will be preferrentially chosen when encoding >10bit content,
>    but that content will normally be YUV420P12 or P016 which should
>    get mapped to P010 and not YUV444P10.
> 
> 2) Transcoding P016 content with nvenc should be possible in a pure
>    hardware pipeline, and that can't be done if nvenc doesn't say it
>    accepts P016. By mapping it to P010, we can use it, albeit with
>    truncation. I have established that swscale doesn't know how to
>    dither to 10bits so we'd get truncation anyway, even if we tried
>    to do this 'properly'.
> 
> Signed-off-by: Philip Langdale <philipl at overt.org>
> ---
>  libavcodec/nvenc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c
> index 161c56adc2..e00c1fb245 100644
> --- a/libavcodec/nvenc.c
> +++ b/libavcodec/nvenc.c
> @@ -41,7 +41,8 @@ const enum AVPixelFormat ff_nvenc_pix_fmts[] = {
>      AV_PIX_FMT_NV12,
>      AV_PIX_FMT_P010,
>      AV_PIX_FMT_YUV444P,
> -    AV_PIX_FMT_YUV444P16,
> +    AV_PIX_FMT_P016,      // Truncated to 10bits
> +    AV_PIX_FMT_YUV444P16, // Truncated to 10bits
>      AV_PIX_FMT_0RGB32,
>      AV_PIX_FMT_0BGR32,
>      AV_PIX_FMT_CUDA,
> @@ -52,6 +53,7 @@ const enum AVPixelFormat ff_nvenc_pix_fmts[] = {
>  };
>  
>  #define IS_10BIT(pix_fmt)  (pix_fmt == AV_PIX_FMT_P010    || \
> +                            pix_fmt == AV_PIX_FMT_P016    || \
>                              pix_fmt == AV_PIX_FMT_YUV444P16)
>  
>  #define IS_YUV444(pix_fmt) (pix_fmt == AV_PIX_FMT_YUV444P || \
> @@ -1222,6 +1224,7 @@ static NV_ENC_BUFFER_FORMAT nvenc_map_buffer_format(enum AVPixelFormat pix_fmt)
>      case AV_PIX_FMT_NV12:
>          return NV_ENC_BUFFER_FORMAT_NV12_PL;
>      case AV_PIX_FMT_P010:
> +    case AV_PIX_FMT_P016:
>          return NV_ENC_BUFFER_FORMAT_YUV420_10BIT;
>      case AV_PIX_FMT_YUV444P:
>          return NV_ENC_BUFFER_FORMAT_YUV444_PL;
> 

It's definitely better than the current situation, and I can't think of
a scenario where it breaks something that's not already broken.
So LGTM from me.

The other patches also look sensible to me, but I'm not the one to Ok them.

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