On Thu, Jan 03, 2019 at 04:21:37PM +0000, Derek Buitenhuis wrote:
> On 03/01/2019 01:33, Michael Niedermayer wrote:
> > The file looks like 2 files concatenated, even with FLV main header between
> > them.
>
> Yes, they all seem to be. I was under the impression FLV didn't have a header
> to
> check against like this. Seems I was wrong.
>
> > the patch below should make this work with sequential demuxing assuming the
> > 2 files dont change streams somehow with the normal demuxer.
> >
> > not sure this is the best way to do it ...
>
> [...]
>
> > also trying a random other flv related tool, FLVTool2 1.0.6 does not seem to
> > demux the 2nd file of the 2 correctly. Which makes me suspect more that the
> > file is invalid. Not that this would fundamentally change anything
>
> Some do, some don't. Classic multimedia.
>
> I would also be OK with a patch that simply stops demuxing like many programs
> seem to do, instead of outputting the packets. Up to you which you prefer; I
> have
> no strong opinion between the two.
>
> > diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
> > index 4b9f46902b..c9423da31c 100644
> > --- a/libavformat/flvdec.c
> > +++ b/libavformat/flvdec.c
>
> [...]
>
> > static int probe(AVProbeData *p, int live)
> > @@ -917,6 +919,17 @@ static int resync(AVFormatContext *s)
> > flv->resync_buffer[j ] =
> > flv->resync_buffer[j1] = avio_r8(s->pb);
> >
> > + if (i >= 8) {
> > + uint8_t *d = flv->resync_buffer + j1 - 8;
> > + if (d[0] == 'F' &&
> > + d[1] == 'L' &&
> > + d[2] == 'V' &&
> > + d[3] < 5 && d[5] == 0) {
> > + av_log(s, AV_LOG_WARNING, "Concatenated FLV detected,
> > might fail to demux, decode and seek %Ld\n", flv->last_ts);
> > + flv->time_offset = flv->last_ts + 1;
> > + }
> > + }
>
> How does this affect seeking? That is, is it safe? If it beaks seeking,
> it may be better to not output the concatenated packets at all.
Heres a better patch which may work with seeking as long as there are only
2 files concatenated
i think completely discarding the parts after the concatenation would cause
user complaints and they would have a point, if the data is in there we
should be able to recover it for muxing it in a better file at least
commit 41db08743da8a624c35d138130379aa1a46d3a53 (HEAD -> master)
Author: Michael Niedermayer <mich...@niedermayer.cc>
Date: Thu Jan 3 01:08:31 2019 +0100
avformat/flvdec: Try to support some concatenated flv files
Fixes: discont.flv
Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
index 4b9f46902b..80bbc5cfeb 100644
--- a/libavformat/flvdec.c
+++ b/libavformat/flvdec.c
@@ -72,6 +72,9 @@ typedef struct FLVContext {
int64_t *keyframe_filepositions;
int missing_streams;
AVRational framerate;
+ int64_t last_ts;
+ int64_t time_offset;
+ int64_t time_pos;
} FLVContext;
static int probe(AVProbeData *p, int live)
@@ -917,6 +920,18 @@ static int resync(AVFormatContext *s)
flv->resync_buffer[j ] =
flv->resync_buffer[j1] = avio_r8(s->pb);
+ if (i >= 8 && pos) {
+ uint8_t *d = flv->resync_buffer + j1 - 8;
+ if (d[0] == 'F' &&
+ d[1] == 'L' &&
+ d[2] == 'V' &&
+ d[3] < 5 && d[5] == 0) {
+ av_log(s, AV_LOG_WARNING, "Concatenated FLV detected, might
fail to demux, decode and seek %Ld\n", flv->last_ts);
+ flv->time_offset = flv->last_ts + 1;
+ flv->time_pos = avio_tell(s->pb);
+ }
+ }
+
if (i > 22) {
unsigned lsize2 = AV_RB32(flv->resync_buffer + j1 - 4);
if (lsize2 >= 11 && lsize2 + 8LL < FFMIN(i, RESYNC_BUFFER_SIZE)) {
@@ -1072,6 +1087,10 @@ skip:
}
av_log(s, AV_LOG_TRACE, "%d %X %d \n", stream_type, flags,
st->discard);
+ if (flv->time_pos <= pos) {
+ dts += flv->time_offset;
+ }
+
if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
((flags & FLV_VIDEO_FRAMETYPE_MASK) == FLV_FRAME_KEY ||
stream_type == FLV_STREAM_TYPE_AUDIO))
@@ -1282,6 +1301,10 @@ leave:
}
}
}
+
+ if (ret >= 0)
+ flv->last_ts = pkt->dts;
+
return ret;
}
[...]
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