Re: [FFmpeg-devel] [PATCH] avformat/mov: Add support for still image AVIF parsing

[Vignesh Venkatasubramanian <vigneshv-at-google.com@ffmpeg.org>]

On Tue, Apr 19, 2022 at 1:18 PM Paul B Mahol <onemda@gmail.com> wrote:
>
>
>
> On Mon, Mar 28, 2022 at 9:12 PM Vignesh Venkatasubramanian <vigneshv-at-google.com@ffmpeg.org> wrote:
>>
>> Add support for parsing AVIF still images. This patches supports
>> AVIF still images that have exactly 1 item (i.e.) no alpha channel.
>> Essentially, we will have to parse the "iloc" box and populate
>> the mov index.
>>
>> With this patch, we can decode still AVIF images like so:
>> ffmpeg -i image.avif image.png
>>
>> Partially fixes trac ticket #7621
>>
>> Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
>> ---
>>  libavformat/isom.h |   1 +
>>  libavformat/mov.c  | 148 +++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 149 insertions(+)
>>
>> diff --git a/libavformat/isom.h b/libavformat/isom.h
>> index 5caf42b15d..02d681e3ae 100644
>> --- a/libavformat/isom.h
>> +++ b/libavformat/isom.h
>> @@ -315,6 +315,7 @@ typedef struct MOVContext {
>>      int have_read_mfra_size;
>>      uint32_t mfra_size;
>>      uint32_t max_stts_delta;
>> +    int is_still_picture_avif;
>>  } MOVContext;
>>
>>  int ff_mp4_read_descr_len(AVIOContext *pb);
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index 6c847de164..fb6d071b95 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -1136,6 +1136,7 @@ static int mov_read_ftyp(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>          c->isom = 1;
>>      av_log(c->fc, AV_LOG_DEBUG, "ISO: File Type Major Brand: %.4s\n",(char *)&type);
>>      av_dict_set(&c->fc->metadata, "major_brand", type, 0);
>> +    c->is_still_picture_avif = !strncmp(type, "avif", 4);
>>      minor_ver = avio_rb32(pb); /* minor version */
>>      av_dict_set_int(&c->fc->metadata, "minor_version", minor_ver, 0);
>>
>> @@ -7430,6 +7431,152 @@ static int mov_read_SAND(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>      return 0;
>>  }
>>
>> +static int rb_size(AVIOContext *pb, uint64_t* value, int size)
>> +{
>> +    if (size == 0) {
>> +        *value = 0;
>> +    } else if (size == 1) {
>> +        *value = avio_r8(pb);
>> +    } else if (size == 2) {
>> +        *value = avio_rb16(pb);
>> +    } else if (size == 4) {
>> +        *value = avio_rb32(pb);
>> +    } else if (size == 8) {
>> +        *value = avio_rb64(pb);
>> +    } else {
>> +        return -1;
>> +    }
>> +    return size;
>> +}
>> +
>> +static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>> +{
>> +    int version, offset_size, length_size, base_offset_size, index_size;
>> +    int item_count, extent_count;
>> +    uint64_t base_offset, extent_offset, extent_length;
>> +    uint8_t value;
>> +    AVStream *st;
>> +    MOVStreamContext *sc;
>> +
>> +    if (!c->is_still_picture_avif) {
>> +        // * For non-avif, we simply ignore the iloc box.
>> +        // * For animated avif, we don't care about the iloc box as all the
>> +        //   necessary information can be found in the moov box.
>> +        return 0;
>> +    }
>> +
>> +    if (c->fc->nb_streams) {
>> +        av_log(c->fc, AV_LOG_INFO, "Duplicate iloc box found\n");
>> +        return 0;
>> +    }
>> +
>> +    st = avformat_new_stream(c->fc, NULL);
>> +    if (!st) {
>> +        return AVERROR(ENOMEM);
>> +    }
>
>
> Here  and everywhere else, remove excessive {/}, they are not needed for one liners.
>

Done.

>> +    st->id = c->fc->nb_streams;
>> +    sc = av_mallocz(sizeof(MOVStreamContext));
>> +    if (!sc) {
>> +        return AVERROR(ENOMEM);
>> +    }
>> +
>> +    st->priv_data = sc;
>> +    st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
>> +    st->codecpar->codec_id = AV_CODEC_ID_AV1;
>> +    sc->ffindex = st->index;
>> +    c->trak_index = st->index;
>> +    st->avg_frame_rate.num = st->avg_frame_rate.den = 1;
>> +    st->time_base.num = st->time_base.den = 1;
>> +    st->nb_frames = 1;
>> +    sc->time_scale = 1;
>> +    sc = st->priv_data;
>> +    sc->pb = c->fc->pb;
>> +    sc->pb_is_copied = 1;
>> +
>> +    version = avio_r8(pb);
>> +    avio_rb24(pb);  // flags.
>> +
>> +    value = avio_r8(pb);
>> +    offset_size = (value >> 4) & 0xF;
>> +    length_size = value & 0xF;
>> +    value = avio_r8(pb);
>> +    base_offset_size = (value >> 4) & 0xF;
>> +    index_size = !version ? 0 : (value & 0xF);
>> +    if (index_size) {
>> +        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.
>> +        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));
>> +    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));
>> +    if (!sc->chunk_offsets) {
>> +        return AVERROR(ENOMEM);
>> +    }
>> +    sc->sample_count = item_count;
>> +    sc->sample_sizes =
>> +        av_malloc_array(item_count, 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));
>> +    if (!sc->stts_data) {
>> +        return AVERROR(ENOMEM);
>> +    }
>> +    sc->stts_data[0].count = 1;
>> +    // Not used for still images. But needed by mov_build_index.
>> +    sc->stts_data[0].duration = 0;
>> +
>> +    for (int i = 0; i < item_count; i++) {
>> +        (version < 2) ? avio_rb16(pb) : avio_rb32(pb);  // item_id;
>> +        if (version > 0) {
>> +            avio_rb16(pb);  // construction_method.
>> +        }
>> +        avio_rb16(pb);  // data_reference_index.
>> +        if (rb_size(pb, &base_offset, base_offset_size) < 0) {
>> +            return AVERROR_INVALIDDATA;
>> +        }
>> +        extent_count = avio_rb16(pb);
>> +        if (extent_count > 1) {
>> +            // For still AVIF images, we only support one extent item.
>> +            return AVERROR_PATCHWELCOME;
>> +        }
>> +        for (int j = 0; j < extent_count; j++) {
>> +            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;
>> +        }
>> +    }
>> +
>> +    mov_build_index(c, st);
>> +
>> +    // For still AVIF images, the iloc box contains all the necessary
>> +    // information that would generally be provided by the moov box. So simply
>> +    // mark that we have found the moov box so that parsing can continue.
>> +    c->found_moov = 1;
>> +
>> +    return atom.size;
>> +}
>> +
>>  static const MOVParseTableEntry mov_default_parse_table[] = {
>>  { MKTAG('A','C','L','R'), mov_read_aclr },
>>  { MKTAG('A','P','R','G'), mov_read_avid },
>> @@ -7532,6 +7679,7 @@ static const MOVParseTableEntry mov_default_parse_table[] = {
>>  { MKTAG('k','i','n','d'), mov_read_kind },
>>  { 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 },
>>  { 0, NULL }
>>  };
>>
>> --
>> 2.35.1.1021.g381101b075-goog
>>
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-- 
Vignesh
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