[FFmpeg-devel] [PATCH]Only test the first frame for malformed bitstreams

[Reimar Döffinger]

On Mon, Mar 25, 2013 at 12:39:17AM +0100, Michael Niedermayer wrote:
> On Mon, Mar 25, 2013 at 12:03:25AM +0100, Carl Eugen Hoyos wrote:
> > Hi!
> > 
> > Currently, the mpegts, the flv and the mov muxer test every h264 / aac frame 
> > for a missing bitstream filter, making remuxing of broken streams impossible.
> > 
> > Testing only the first frame should be sufficient to inform the user of a 
> > missing bitstream filter.
> > 
> > Attached patches fix tickets #1758 and #2380, I tested the remuxed files 
> > successfully with WMP and QT.
> > 
> > Please review, Carl Eugen
> 
> >  mpegtsenc.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > bdc3c59730f4da7cb36f7709b42a418574f4afeb  patch264ts.diff
> > diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
> > index 7016774..617b9a7 100644
> > --- a/libavformat/mpegtsenc.c
> > +++ b/libavformat/mpegtsenc.c
> > @@ -1093,7 +1093,7 @@ static int mpegts_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
> >          const uint8_t *p = buf, *buf_end = p+size;
> >          uint32_t state = -1;
> >  
> > -        if (pkt->size < 5 || AV_RB32(pkt->data) != 0x0000001) {
> > +        if (!st->codec->frame_number && (pkt->size < 5 || AV_RB32(pkt->data) != 0x0000001)) {
> >              av_log(s, AV_LOG_ERROR, "H.264 bitstream malformed, "
> >                     "no startcode found, use the h264_mp4toannexb bitstream filter (-bsf h264_mp4toannexb)\n");
> >              return AVERROR(EINVAL);
> 
> at least a warning should still be printed also
> st->nb_frames seems more correct than st->codec->frame_number if
> it works

This doesn't make much sense, should checking this condition only
on the first frame break the test for most streams?
I believe e.g. a TS e.g. from a BluRay should always still start
with a startcode, even if not bitstream filter is used.
At the same time, unless the bitstream filter throws away data
(in which case I think it is buggy), adding it will not
fix a stream not starting with a startcode.
Or in other words, I have the feeling this whole code is just
nonsense anyway, and adding more hacks on top of it won't make
it better.