[FFmpeg-devel] [PATCH] Save FFmpeg colorspace info in openh264 video files.

[James Almer]

On 12/1/2016 6:26 PM, Gregory J. Wolfe wrote:
> As of version 1.6, libopenh264 saves (in the output video file)
> information about the color primaries, transfer characteristics,
> and color matrix used when the video pixel data was created.
> This patch sets the required libopenh264 data structures using
> the FFmpeg colorspace information so that video players will
> know how to properly decode video files created using FFmpeg
> and libopenh264.
> 
> Signed-off-by: Gregory J. Wolfe <gregory.wolfe at kodakalaris.com>
> ---
>  libavcodec/libopenh264enc.c | 49 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 
> diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
> index e84de27..3b019b8 100644
> --- a/libavcodec/libopenh264enc.c
> +++ b/libavcodec/libopenh264enc.c
> @@ -205,6 +205,55 @@ FF_ENABLE_DEPRECATION_WARNINGS
>          }
>      }
>  
> +#if OPENH264_VER_AT_LEAST(1, 6)
> +    // set video signal type information
> +    param.sSpatialLayers[0].bVideoSignalTypePresent = true;
> +    param.sSpatialLayers[0].uiVideoFormat = VF_UNDEF; // default; choices are VF_: COMPONENT, PAL, NTSC, SECAM, MAC, UNDEF
> +    param.sSpatialLayers[0].bFullRange = avctx->color_range == AVCOL_RANGE_JPEG;
> +    param.sSpatialLayers[0].bColorDescriptionPresent = true;
> +    switch (avctx->color_primaries) {
> +    case AVCOL_PRI_BT709:        param.sSpatialLayers[0].uiColorPrimaries          = CP_BT709;         break;
> +    case AVCOL_PRI_UNSPECIFIED:  param.sSpatialLayers[0].uiColorPrimaries          = CP_UNDEF;         break;
> +    case AVCOL_PRI_BT470M:       param.sSpatialLayers[0].uiColorPrimaries          = CP_BT470M;        break;
> +    case AVCOL_PRI_BT470BG:      param.sSpatialLayers[0].uiColorPrimaries          = CP_BT470BG;       break;
> +    case AVCOL_PRI_SMPTE170M:    param.sSpatialLayers[0].uiColorPrimaries          = CP_SMPTE170M;     break;
> +    case AVCOL_PRI_SMPTE240M:    param.sSpatialLayers[0].uiColorPrimaries          = CP_SMPTE240M;     break;
> +    case AVCOL_PRI_FILM:         param.sSpatialLayers[0].uiColorPrimaries          = CP_FILM;          break;
> +    case AVCOL_PRI_BT2020:       param.sSpatialLayers[0].uiColorPrimaries          = CP_BT2020;        break;
> +    default:                     param.sSpatialLayers[0].uiColorPrimaries          = CP_UNDEF;         break;
> +    }
> +    switch (avctx->color_trc) {
> +    case AVCOL_TRC_BT709:        param.sSpatialLayers[0].uiTransferCharacteristics = TRC_BT709;        break;
> +    case AVCOL_TRC_UNSPECIFIED:  param.sSpatialLayers[0].uiTransferCharacteristics = TRC_UNDEF;        break;
> +    case AVCOL_TRC_GAMMA22:      param.sSpatialLayers[0].uiTransferCharacteristics = TRC_BT470M;       break;
> +    case AVCOL_TRC_GAMMA28:      param.sSpatialLayers[0].uiTransferCharacteristics = TRC_BT470BG;      break;
> +    case AVCOL_TRC_SMPTE170M:    param.sSpatialLayers[0].uiTransferCharacteristics = TRC_SMPTE170M;    break;
> +    case AVCOL_TRC_SMPTE240M:    param.sSpatialLayers[0].uiTransferCharacteristics = TRC_SMPTE240M;    break;
> +    case AVCOL_TRC_LINEAR:       param.sSpatialLayers[0].uiTransferCharacteristics = TRC_LINEAR;       break;
> +    case AVCOL_TRC_LOG:          param.sSpatialLayers[0].uiTransferCharacteristics = TRC_LOG100;       break;
> +    case AVCOL_TRC_LOG_SQRT:     param.sSpatialLayers[0].uiTransferCharacteristics = TRC_LOG316;       break;
> +    case AVCOL_TRC_IEC61966_2_4: param.sSpatialLayers[0].uiTransferCharacteristics = TRC_IEC61966_2_4; break;
> +    case AVCOL_TRC_BT1361_ECG:   param.sSpatialLayers[0].uiTransferCharacteristics = TRC_BT1361E;      break;
> +    case AVCOL_TRC_IEC61966_2_1: param.sSpatialLayers[0].uiTransferCharacteristics = TRC_IEC61966_2_1; break;
> +    case AVCOL_TRC_BT2020_10:    param.sSpatialLayers[0].uiTransferCharacteristics = TRC_BT2020_10;    break;
> +    case AVCOL_TRC_BT2020_12:    param.sSpatialLayers[0].uiTransferCharacteristics = TRC_BT2020_12;    break;
> +    default:                     param.sSpatialLayers[0].uiTransferCharacteristics = TRC_UNDEF;        break;
> +    }
> +    switch (avctx->colorspace) {
> +    case AVCOL_SPC_RGB:          param.sSpatialLayers[0].uiColorMatrix             = CM_GBR;           break;
> +    case AVCOL_SPC_BT709:        param.sSpatialLayers[0].uiColorMatrix             = CM_BT709;         break;
> +    case AVCOL_SPC_UNSPECIFIED:  param.sSpatialLayers[0].uiColorMatrix             = CM_UNDEF;         break;
> +    case AVCOL_SPC_FCC:          param.sSpatialLayers[0].uiColorMatrix             = CM_FCC;           break;
> +    case AVCOL_SPC_BT470BG:      param.sSpatialLayers[0].uiColorMatrix             = CM_BT470BG;       break;
> +    case AVCOL_SPC_SMPTE170M:    param.sSpatialLayers[0].uiColorMatrix             = CM_SMPTE170M;     break;
> +    case AVCOL_SPC_SMPTE240M:    param.sSpatialLayers[0].uiColorMatrix             = CM_SMPTE240M;     break;
> +    case AVCOL_SPC_YCOCG:        param.sSpatialLayers[0].uiColorMatrix             = CM_YCGCO;         break;
> +    case AVCOL_SPC_BT2020_NCL:   param.sSpatialLayers[0].uiColorMatrix             = CM_BT2020NC;      break;
> +    case AVCOL_SPC_BT2020_CL:    param.sSpatialLayers[0].uiColorMatrix             = CM_BT2020C;       break;
> +    default:                     param.sSpatialLayers[0].uiColorMatrix             = CM_UNDEF;         break;
> +    }

Are you 100% sure these CP_ enums aren't the same as our AVCOL_ ones?
You should be able to simplify this to

param.sSpatialLayers[0].uiColorPrimaries =avctx->color_primaries;
param.sSpatialLayers[0].uiTransferCharacteristics = avctx->color_trc;
param.sSpatialLayers[0].uiColorMatrix = avctx->colorspace;

if libopen264 choose to follow the spec values. Which I'd find odd if they
didn't.

And assuming you're filtering values not supported by libopen264, shouldn't
the library simply refuse them and abort encoding at init? That'd be IMO
better than letting the user set for example SMPTE2084 trc and the encoder
silently turning that into undefined.

Note how the colorspace filter refuses values it doesn't support.