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 <vigne...@google.com>
---
libavformat/isom.h | 1 +
libavformat/mov.c | 137 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 138 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..e925690584 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 +7431,141 @@ 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);
+ 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 +7668,7 @@ 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 }
};
--
2.36.0.rc0.470.gd361397f0d-goog
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