On 5/16/2019 7:29 PM, Andreas Rheinhardt wrote:
> The earlier code relied on the length of clusters always being coded on
> eight bytes as was the behaviour of libavformat's Matroska muxer until
> recently. But given that our own Matroska muxer now (and mkvmerge from
> time immemorial) creates files that don't conform to this assumption,
> it is high time to get rid of this assumption.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@gmail.com>
> ---
> I originally planed for this patch to get merged before my Matroska muxer
> patches.
> libavformat/matroskadec.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> index 4dd933ef74..6fd5537f5a 100644
> --- a/libavformat/matroskadec.c
> +++ b/libavformat/matroskadec.c
> @@ -3711,15 +3711,17 @@ static int
> webm_clusters_start_with_keyframe(AVFormatContext *s)
> cluster_pos = s->streams[0]->index_entries[index].pos;
> before_pos = avio_tell(s->pb);
> while (1) {
> - int64_t cluster_id = 0, cluster_length = 0;
> + uint64_t cluster_id, cluster_length;
> + int read;
> AVPacket *pkt;
> avio_seek(s->pb, cluster_pos, SEEK_SET);
> // read cluster id and length
> - ebml_read_num(matroska, matroska->ctx->pb, 4, &cluster_id);
> - ebml_read_length(matroska, matroska->ctx->pb, &cluster_length);
> - if (cluster_id != 0xF43B675) { // done with all clusters
> + read = ebml_read_num(matroska, matroska->ctx->pb, 4, &cluster_id);
> + if (read < 0 || cluster_id != 0xF43B675) // done with all clusters
This could be changed to use the matroska.h define instead.
> + break;
> + read = ebml_read_length(matroska, matroska->ctx->pb,
> &cluster_length);
> + if (read < 0)
> break;
> - }
> avio_seek(s->pb, cluster_pos, SEEK_SET);
> matroska->current_id = 0;
> matroska_clear_queue(matroska);
> @@ -3728,7 +3730,8 @@ static int
> webm_clusters_start_with_keyframe(AVFormatContext *s)
> break;
> }
> pkt = &matroska->queue->pkt;
> - cluster_pos += cluster_length + 12; // 12 is the offset of the
> cluster id and length.
> + // 4 + read is the length of the cluster id and the cluster length
> field.
> + cluster_pos += 4 + read + cluster_length;
> if (!(pkt->flags & AV_PKT_FLAG_KEY)) {
> rv = 0;
> break;
Applied, thanks.
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