[FFmpeg-devel] [PATCH v2 2/3] pngdec: expose gAMA and cHRM chunks as side data

[James Almer]

On 9/25/2017 4:28 PM, Rostislav Pehlivanov wrote:
> Signed-off-by: Rostislav Pehlivanov <atomnuker at gmail.com>
> ---
>  libavcodec/pngdec.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
> 
> diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
> index 0d6612ccca..2d005f90fc 100644
> --- a/libavcodec/pngdec.c
> +++ b/libavcodec/pngdec.c
> @@ -25,6 +25,7 @@
>  #include "libavutil/bprint.h"
>  #include "libavutil/imgutils.h"
>  #include "libavutil/stereo3d.h"
> +#include "libavutil/mastering_display_metadata.h"
>  
>  #include "avcodec.h"
>  #include "bytestream.h"
> @@ -1287,6 +1288,53 @@ static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s,
>                  goto fail;
>              break;
>          }
> +        case MKTAG('c', 'H', 'R', 'M'): {
> +            AVMasteringDisplayMetadata *mdm = av_mastering_display_metadata_create_side_data(p);
> +            if (!mdm) {
> +                ret = AVERROR(ENOMEM);
> +                goto fail;
> +            }
> +
> +            mdm->white_point[0].num = bytestream2_get_be32(&s->gb);
> +            mdm->white_point[0].den = 100000;
> +            mdm->white_point[1].num = bytestream2_get_be32(&s->gb);
> +            mdm->white_point[1].den = 100000;
> +
> +            /* Red primaries */
> +            mdm->display_primaries[0][0].num = bytestream2_get_be32(&s->gb);
> +            mdm->display_primaries[0][0].den = 100000;
> +            mdm->display_primaries[0][1].num = bytestream2_get_be32(&s->gb);
> +            mdm->display_primaries[0][1].den = 100000;
> +
> +            /* Green primaries */
> +            mdm->display_primaries[1][0].num = bytestream2_get_be32(&s->gb);
> +            mdm->display_primaries[1][0].den = 100000;
> +            mdm->display_primaries[1][1].num = bytestream2_get_be32(&s->gb);
> +            mdm->display_primaries[1][1].den = 100000;
> +
> +            /* Blue primaries */
> +            mdm->display_primaries[2][0].num = bytestream2_get_be32(&s->gb);
> +            mdm->display_primaries[2][0].den = 100000;
> +            mdm->display_primaries[2][1].num = bytestream2_get_be32(&s->gb);
> +            mdm->display_primaries[2][1].den = 100000;

Consider using av_make_q(). It should make this shorter and cleaner.

> +
> +            mdm->has_primaries = 1;
> +            bytestream2_skip(&s->gb, 4); /* crc */

Unrelated to this patch, but not doing CRC checks on demand (that is,
when err_detect enables it) seems like bad practice, especially for
lossless codecs.

> +            break;
> +        }
> +        case MKTAG('g', 'A', 'M', 'A'): {
> +            AVFrameSideData *sd = av_frame_new_side_data(p, AV_FRAME_DATA_GAMMA, sizeof(AVRational));
> +            AVRational *gamma = (AVRational *)sd->data;

sd may be NULL. The check below should be first.

> +            if (!sd) {
> +                ret = AVERROR(ENOMEM);
> +                goto fail;
> +            }
> +
> +            gamma->num = bytestream2_get_be32(&s->gb);
> +            gamma->den = 100000;
> +            bytestream2_skip(&s->gb, 4); /* crc */
> +            break;
> +        }
>          case MKTAG('I', 'E', 'N', 'D'):
>              if (!(s->pic_state & PNG_ALLIMAGE))
>                  av_log(avctx, AV_LOG_ERROR, "IEND without all image\n");
>