Bug#789254: This sample seems not to be processable by FFmpeg

[Petter Reinholdtsen]

[Peter Belkner]
> I was testing with Winamp and the FFmpeg based "in_ffsox" input plugin. 
> It was not "stuttering" at all. I discovered "stuttering" only when 
> testing with VLC player.

Aha.

> Meanwhile I've learned that we have two issues:
>
>  1. "20030213-cvs.mpeg" had not processed at all (i.e. just loudness
>     analysis was aborting with an error and hence it could not have
>     "stuttered")
>  2. "DavidGallo_2007.dv" stutters.

Aha.  That is strange, as I am quite sure I tested it before reporting
the bug.  Anyway, I trust your observations and must remember
incorrectly.

> The (previous) patch solves the first issue. The idea is to throw away
> packages FFmpeg cannot deal with.

Given that it only happen once, I guess the package is at the start or
at the end.  Perhaps the message should be extended to mention how far
into the stream the package is dropped.

Am I right in believing that many such dropped packages in the middle of
the stream will cause audio and video to get out of sync?

> The following patch solves "stuttering" (but really is some kind of a 
> "sledgehammer")
>
>     diff -rc ./bs1770gain-0.4.4-beta2/libffsox-2/ffsox_frame_writer.c ./bs1770gain-0.4.4-beta3/libffsox-2/ffsox_frame_writer.c
>     *** ./bs1770gain-0.4.4-beta2/libffsox-2/ffsox_frame_writer.c	2015-06-14 18:11:19.000000000 +0200
>     --- ./bs1770gain-0.4.4-beta3/libffsox-2/ffsox_frame_writer.c	2015-06-22 09:12:36.000000000 +0200
>     ***************
>     *** 145,150 ****
>     --- 145,154 ----
>        
>          if (0!=*got_packet) {
>            av_packet_rescale_ts(pkt,cc->time_base,st->time_base);
>     +     // where do the "magic" factor 0.5 come from?
>     +     pkt->dts>>=1;
>     +     pkt->pts>>=1;
>     +     pkt->duration>>=1;
>        
>            if (ffsox_stream_interleaved_write(so,pkt)<0) {
>              DMESSAGE("writing packet");
>
> Maybe Carl Eugen can provide some insight into how to align the time 
> scales between streams.

I tested and this solve the stuttering for me too, but I have no idea
about the mathematics involved here.

-- 
Happy hacking
Petter Reinholdtsen