[FFmpeg-devel] [PATCH] avformat/mov: Only read the primary item for AVIF

[Vignesh Venkatasubramanian]

On Sun, Apr 24, 2022 at 11:35 AM Vignesh Venkatasubramanian
<vigneshv at google.com> wrote:
>
> Update the still AVIF parser to only read the primary item. With this
> patch, AVIF still images with exif/icc/alpha channel will no longer
> fail to parse.
>
> For example, this patch enables parsing of files in:
> https://github.com/AOMediaCodec/av1-avif/tree/master/testFiles/Microsoft
>
> Partially fixes trac ticket #7621
>
> Signed-off-by: Vignesh Venkatasubramanian <vigneshv at google.com>
> ---
>  libavformat/isom.h |  1 +
>  libavformat/mov.c  | 41 +++++++++++++++++++++--------------------
>  2 files changed, 22 insertions(+), 20 deletions(-)
>
> diff --git a/libavformat/isom.h b/libavformat/isom.h
> index cf36f04d5b..f05c2d9c28 100644
> --- a/libavformat/isom.h
> +++ b/libavformat/isom.h
> @@ -317,6 +317,7 @@ typedef struct MOVContext {
>      uint32_t mfra_size;
>      uint32_t max_stts_delta;
>      int is_still_picture_avif;
> +    int primary_item_id;
>  } MOVContext;
>
>  int ff_mp4_read_descr_len(AVIOContext *pb);
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 3e83e54a77..6be0f317ca 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -7449,6 +7449,13 @@ static int rb_size(AVIOContext *pb, uint64_t* value, int size)
>      return size;
>  }
>
> +static int mov_read_pitm(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> +{
> +    avio_rb32(pb);  // version & flags.
> +    c->primary_item_id = avio_rb16(pb);
> +    return atom.size;
> +}
> +
>  static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>  {
>      int version, offset_size, length_size, base_offset_size, index_size;
> @@ -7505,34 +7512,25 @@ static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>          return AVERROR_PATCHWELCOME;
>      }
>      item_count = (version < 2) ? avio_rb16(pb) : avio_rb32(pb);
> -    if (item_count > 1) {
> -        // For still AVIF images, we only support one item. Second item will
> -        // generally be found for AVIF images with alpha channel. We don't
> -        // support them as of now.
> -        av_log(c->fc, AV_LOG_ERROR, "iloc: item_count > 1 not supported.\n");
> -        return AVERROR_PATCHWELCOME;
> -    }
>
>      // Populate the necessary fields used by mov_build_index.
> -    sc->stsc_count = item_count;
> -    sc->stsc_data = av_malloc_array(item_count, sizeof(*sc->stsc_data));
> +    sc->stsc_count = 1;
> +    sc->stsc_data = av_malloc_array(1, sizeof(*sc->stsc_data));
>      if (!sc->stsc_data)
>          return AVERROR(ENOMEM);
>      sc->stsc_data[0].first = 1;
>      sc->stsc_data[0].count = 1;
>      sc->stsc_data[0].id = 1;
> -    sc->chunk_count = item_count;
> -    sc->chunk_offsets =
> -        av_malloc_array(item_count, sizeof(*sc->chunk_offsets));
> +    sc->chunk_count = 1;
> +    sc->chunk_offsets = av_malloc_array(1, sizeof(*sc->chunk_offsets));
>      if (!sc->chunk_offsets)
>          return AVERROR(ENOMEM);
> -    sc->sample_count = item_count;
> -    sc->sample_sizes =
> -        av_malloc_array(item_count, sizeof(*sc->sample_sizes));
> +    sc->sample_count = 1;
> +    sc->sample_sizes = av_malloc_array(1, sizeof(*sc->sample_sizes));
>      if (!sc->sample_sizes)
>          return AVERROR(ENOMEM);
> -    sc->stts_count = item_count;
> -    sc->stts_data = av_malloc_array(item_count, sizeof(*sc->stts_data));
> +    sc->stts_count = 1;
> +    sc->stts_data = av_malloc_array(1, sizeof(*sc->stts_data));
>      if (!sc->stts_data)
>          return AVERROR(ENOMEM);
>      sc->stts_data[0].count = 1;
> @@ -7540,7 +7538,7 @@ static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>      sc->stts_data[0].duration = 0;
>
>      for (int i = 0; i < item_count; i++) {
> -        (version < 2) ? avio_rb16(pb) : avio_rb32(pb);  // item_id;
> +        int item_id = (version < 2) ? avio_rb16(pb) : avio_rb32(pb);
>          if (version > 0)
>              avio_rb16(pb);  // construction_method.
>          avio_rb16(pb);  // data_reference_index.
> @@ -7556,8 +7554,10 @@ static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>              if (rb_size(pb, &extent_offset, offset_size) < 0 ||
>                  rb_size(pb, &extent_length, length_size) < 0)
>                  return AVERROR_INVALIDDATA;
> -            sc->sample_sizes[0] = extent_length;
> -            sc->chunk_offsets[0] = base_offset + extent_offset;
> +            if (item_id == c->primary_item_id) {
> +                sc->sample_sizes[0] = extent_length;
> +                sc->chunk_offsets[0] = base_offset + extent_offset;
> +            }
>          }
>      }
>
> @@ -7674,6 +7674,7 @@ static const MOVParseTableEntry mov_default_parse_table[] = {
>  { MKTAG('S','A','3','D'), mov_read_SA3D }, /* ambisonic audio box */
>  { MKTAG('S','A','N','D'), mov_read_SAND }, /* non diegetic audio box */
>  { MKTAG('i','l','o','c'), mov_read_iloc },
> +{ MKTAG('p','i','t','m'), mov_read_pitm },
>  { 0, NULL }
>  };
>
> --
> 2.36.0.rc2.479.g8af0fa9b8e-goog
>

Any comments on this one? If not, can this be merged please? :)

-- 
Vignesh