On 10 Apr 2025, at 11:03, Dimitry Andric <dimi...@unified-streaming.com> wrote:
>
> On 3 Apr 2025, at 22:02, Dimitry Andric <dimi...@unified-streaming.com> wrote:
>>
>> When decoding fragmented MP4 files that have an empty stsc box, and
>> instead contain sample description indexes in their tfhd boxes, the mov
>> demuxer does not notify the decoder whenever the current sample
>> description index changes. If the SPS or PPS changed sufficiently, this
>> can lead to unexpected decoding errors.
>>
>> To fix this, in mov_finalize_packet(), when stsc_data is not available,
>> use get_frag_stream_info_from_pkt() to get at the current fragment
>> stream info, and retrieve the current sample description index from
>> there. Then use that index in a similar manner as the stsc case.
>>
>> Signed-off-by: Dimitry Andric <dimi...@unified-streaming.com>
>> ---
>> libavformat/mov.c | 50 ++++++++++++++++++++++++++++-------------------
>> 1 file changed, 30 insertions(+), 20 deletions(-)
>>
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index 452690090c..ead89192f4 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -10756,25 +10756,29 @@ static int mov_switch_root(AVFormatContext *s,
>> int64_t target, int index)
>> return 1;
>> }
>>
>> -static int mov_change_extradata(AVStream *st, AVPacket *pkt)
>> +static int mov_change_extradata(AVStream *st, AVPacket *pkt, int stsd_id)
>> {
>> MOVStreamContext *sc = st->priv_data;
>> uint8_t *side, *extradata;
>> int extradata_size;
>>
>> - /* Save the current index. */
>> - sc->last_stsd_index = sc->stsc_data[sc->stsc_index].id - 1;
>> + if (stsd_id > 0 &&
>> + stsd_id - 1 < sc->stsd_count &&
>> + stsd_id - 1 != sc->last_stsd_index) {
>> + /* Save the current index. */
>> + sc->last_stsd_index = stsd_id - 1;
>>
>> - /* Notify the decoder that extradata changed. */
>> - extradata_size = sc->extradata_size[sc->last_stsd_index];
>> - extradata = sc->extradata[sc->last_stsd_index];
>> - if (st->discard != AVDISCARD_ALL && extradata_size > 0 && extradata) {
>> - side = av_packet_new_side_data(pkt,
>> - AV_PKT_DATA_NEW_EXTRADATA,
>> - extradata_size);
>> - if (!side)
>> - return AVERROR(ENOMEM);
>> - memcpy(side, extradata, extradata_size);
>> + /* Notify the decoder that extradata changed. */
>> + extradata_size = sc->extradata_size[sc->last_stsd_index];
>> + extradata = sc->extradata[sc->last_stsd_index];
>> + if (st->discard != AVDISCARD_ALL && extradata_size > 0 &&
>> extradata) {
>> + side = av_packet_new_side_data(pkt,
>> + AV_PKT_DATA_NEW_EXTRADATA,
>> + extradata_size);
>> + if (!side)
>> + return AVERROR(ENOMEM);
>> + memcpy(side, extradata, extradata_size);
>> + }
>> }
>>
>> return 0;
>> @@ -10893,13 +10897,10 @@ static int mov_finalize_packet(AVFormatContext *s,
>> AVStream *st, AVIndexEntry *s
>>
>> /* Multiple stsd handling. */
>> if (sc->stsc_data) {
>> - if (sc->stsc_data[sc->stsc_index].id > 0 &&
>> - sc->stsc_data[sc->stsc_index].id - 1 < sc->stsd_count &&
>> - sc->stsc_data[sc->stsc_index].id - 1 != sc->last_stsd_index) {
>> - int ret = mov_change_extradata(st, pkt);
>> - if (ret < 0)
>> - return ret;
>> - }
>> + int stsd_id = sc->stsc_data[sc->stsc_index].id;
>> + int ret = mov_change_extradata(st, pkt, stsd_id);
>> + if (ret < 0)
>> + return ret;
>>
>> /* Update the stsc index for the next sample */
>> sc->stsc_sample++;
>> @@ -10908,6 +10909,15 @@ static int mov_finalize_packet(AVFormatContext *s,
>> AVStream *st, AVIndexEntry *s
>> sc->stsc_index++;
>> sc->stsc_sample = 0;
>> }
>> + } else {
>> + MOVContext *mov = s->priv_data;
>> + MOVFragmentStreamInfo *frag_stream_info =
>> get_frag_stream_info_from_pkt(&mov->frag_index, pkt, sc->id);
>> + if (frag_stream_info) {
>> + int stsd_id = frag_stream_info->stsd_id;
>> + int ret = mov_change_extradata(st, pkt, stsd_id);
>> + if (ret < 0)
>> + return ret;
>> + }
>> }
>>
>> return 0;
>> --
>> 2.43.0
>>
>
> Any comments on this patch?
Ping :)
-Dimitry
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