[FFmpeg-devel] [PATCH 1/2] avformat/mvdec: make audio stream conditional
John-Paul Stewart
jpstewart at personalprojects.net
Fri Dec 31 21:50:18 EET 2021
Only allocate an audio stream if there is one in the data. Silicon
Graphics movie format will contain default values (16 bit samples, 2
audio channels, 22050 Hz sample rate) even when no audio is present in
the file. This confuses FFmpeg into thinking such an audio stream is
present with 0 samples in it.
There is a flag value in the format to indicate whether or not audio is
present. This patch checks that and behaves accordingly.
Signed-off-by: John-Paul Stewart <jpstewart at personalprojects.net>
---
libavformat/mvdec.c | 33 ++++++++++++++++++++++++---------
1 file changed, 24 insertions(+), 9 deletions(-)
diff --git a/libavformat/mvdec.c b/libavformat/mvdec.c
index ea955d2b11..7493bcc762 100644
--- a/libavformat/mvdec.c
+++ b/libavformat/mvdec.c
@@ -45,6 +45,10 @@ typedef struct MvContext {
int aformat; ///< audio format
} MvContext;
+/* these magic numbers are defined in moviefile.h on Silicon Grahpics IRIX */
+#define MOVIE_SOUND 1
+#define MOVIE_SILENT 2
+
#define AUDIO_FORMAT_SIGNED 401
static int mv_probe(const AVProbeData *p)
@@ -305,20 +309,27 @@ static int mv_read_header(AVFormatContext *avctx)
avio_skip(pb, 10);
- /* allocate audio track first to prevent unnecessary seeking
- * (audio packet always precede video packet for a given frame) */
- ast = avformat_new_stream(avctx, NULL);
- if (!ast)
- return AVERROR(ENOMEM);
-
vst = avformat_new_stream(avctx, NULL);
if (!vst)
return AVERROR(ENOMEM);
fps = av_d2q(av_int2double(avio_rb64(pb)), INT_MAX);
avpriv_set_pts_info(vst, 64, fps.den, fps.num);
- avio_skip(pb, 4);
vst->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
vst->avg_frame_rate = fps;
+
+ v = avio_rb16(pb);
+ if (v == MOVIE_SOUND) {
+ /* movie has sound, so allocate an audio stream */
+ ast = avformat_new_stream(avctx, NULL);
+ if (!ast)
+ return AVERROR(ENOMEM);
+
+ ast->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
+ } else if (v != MOVIE_SILENT)
+ return AVERROR_INVALIDDATA;
+
+ avio_skip(pb, 2);
+
vst->duration = vst->nb_frames = avio_rb32(pb);
v = avio_rb32(pb);
switch (v) {
@@ -338,7 +349,7 @@ static int mv_read_header(AVFormatContext *avctx)
vst->codecpar->height = avio_rb32(pb);
avio_skip(pb, 12);
- ast->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
+ if (ast) {
ast->nb_frames = vst->nb_frames;
ast->codecpar->sample_rate = avio_rb32(pb);
if (ast->codecpar->sample_rate <= 0) {
@@ -373,6 +384,8 @@ static int mv_read_header(AVFormatContext *avctx)
return AVERROR_INVALIDDATA;
avio_skip(pb, 8);
+ } else
+ avio_skip(pb, 24); /* skip meaningless audio metadata */
var_read_metadata(avctx, "title", 0x80);
var_read_metadata(avctx, "comment", 0x100);
@@ -386,9 +399,11 @@ static int mv_read_header(AVFormatContext *avctx)
if (avio_feof(pb))
return AVERROR_INVALIDDATA;
avio_skip(pb, 8);
+ if (ast) {
av_add_index_entry(ast, pos, timestamp, asize, 0, AVINDEX_KEYFRAME);
- av_add_index_entry(vst, pos + asize, i, vsize, 0, AVINDEX_KEYFRAME);
timestamp += asize / (ast->codecpar->channels * (uint64_t)bytes_per_sample);
+ }
+ av_add_index_entry(vst, pos + asize, i, vsize, 0, AVINDEX_KEYFRAME);
}
} else if (!version && avio_rb16(pb) == 3) {
avio_skip(pb, 4);
--
2.34.1
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