[FFmpeg-devel] [PATCH] libavformat/mov: Accept known codepoints in 'colr'

[Steven Robertson]

Hey folks,

We anticipate professional video software will start producing files with
the expanded codepoints Real Soon Now, and ProRes already supports Rec.
2020 and ST 2084 (see SMPTE RDD 36), so presumably MOV will get some of
that soon too. (QuickTime in OS X El Cap already recognizes Rec. 2020 color
in MOV, even though TN 2162 hasn't been updated yet.) Also it'd be nice to
land this for the bugfix in SD. Anything I can do to help with the review?

Thanks!
Steve

On Wed, Aug 17, 2016 at 12:25 AM, Steven Robertson <steven at strobe.cc> wrote:

> This change relaxes the whitelist on reading color metadata in MOV/BMFF
> containers. The whitelist on writing values is still in place.
>
> As a consequence it also fixes an apparent bug in reading 'nclc' values.
> The 'nclc' spec [1] is in harmony with ISO 23001-8 for the values it
> lists, but the code getting removed was remapping 5->6 and 6->7 for
> primaries, which is incorrect, and was remapping 6->5 for color matrix
> ("colorspace" in the code), which is equivalent but an unnecessary
> inconsistency. This logic error doesn't appear in movenc.
>
> Removing the whitelist allows proper conversion when the source codec
> relies on the container for proper signaling of newer codepoints, such
> as DNxHR and VP9. If converting to a codec or container that has updated
> its spec to include the new codepoints, the metadata will be preserved.
> If going back to MOV/BMFF, the output whitelist will still kick in, so
> this won't result in out-of-spec files being created.
>
> [1] https://developer.apple.com/library/mac/technotes/tn2162/_index.html
>
> Signed-off-by: Steven Robertson <steven at strobe.cc>
> ---
>  libavformat/mov.c | 40 +++++++++-------------------------------
>  1 file changed, 9 insertions(+), 31 deletions(-)
>
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 7c8f784..6450d52 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -1324,38 +1324,16 @@ static int mov_read_colr(MOVContext *c,
> AVIOContext *pb, MOVAtom atom)
>              st->codecpar->color_range = AVCOL_RANGE_JPEG;
>          else
>              st->codecpar->color_range = AVCOL_RANGE_MPEG;
> -        /* 14496-12 references JPEG XR specs (rather than the more
> complete
> -         * 23001-8) so some adjusting is required */
> -        if (color_primaries >= AVCOL_PRI_FILM)
> -            color_primaries = AVCOL_PRI_UNSPECIFIED;
> -        if ((color_trc >= AVCOL_TRC_LINEAR &&
> -             color_trc <= AVCOL_TRC_LOG_SQRT) ||
> -            color_trc >= AVCOL_TRC_BT2020_10)
> -            color_trc = AVCOL_TRC_UNSPECIFIED;
> -        if (color_matrix >= AVCOL_SPC_BT2020_NCL)
> -            color_matrix = AVCOL_SPC_UNSPECIFIED;
> -        st->codecpar->color_primaries = color_primaries;
> -        st->codecpar->color_trc       = color_trc;
> -        st->codecpar->color_space     = color_matrix;
> -    } else if (!strncmp(color_parameter_type, "nclc", 4)) {
> -        /* color primaries, Table 4-4 */
> -        switch (color_primaries) {
> -        case 1: st->codecpar->color_primaries = AVCOL_PRI_BT709; break;
> -        case 5: st->codecpar->color_primaries = AVCOL_PRI_SMPTE170M;
> break;
> -        case 6: st->codecpar->color_primaries = AVCOL_PRI_SMPTE240M;
> break;
> -        }
> -        /* color transfer, Table 4-5 */
> -        switch (color_trc) {
> -        case 1: st->codecpar->color_trc = AVCOL_TRC_BT709; break;
> -        case 7: st->codecpar->color_trc = AVCOL_TRC_SMPTE240M; break;
> -        }
> -        /* color matrix, Table 4-6 */
> -        switch (color_matrix) {
> -        case 1: st->codecpar->color_space = AVCOL_SPC_BT709; break;
> -        case 6: st->codecpar->color_space = AVCOL_SPC_BT470BG; break;
> -        case 7: st->codecpar->color_space = AVCOL_SPC_SMPTE240M; break;
> -        }
>      }
> +    if (color_primaries >= AVCOL_PRI_NB)
> +        color_primaries = AVCOL_PRI_UNSPECIFIED;
> +    if (color_trc >= AVCOL_TRC_NB)
> +        color_trc = AVCOL_TRC_UNSPECIFIED;
> +    if (color_matrix >= AVCOL_SPC_NB)
> +        color_matrix = AVCOL_SPC_UNSPECIFIED;
> +    st->codecpar->color_primaries = color_primaries;
> +    st->codecpar->color_trc       = color_trc;
> +    st->codecpar->color_space     = color_matrix;
>      av_log(c->fc, AV_LOG_TRACE, "\n");
>
>      return 0;
> --
> 2.8.0.rc2
>
>