ffmpeg SCR moves backwards in output muxed mpeg file

[johnnyquid]

I am not sure where to properly post bug reports so bear with me that I also posted in the ffmpeg-users as well. The issue was reported in Oct 2010 and fixed but the fix does not always seem to work. See ​http://ffmpeg-users.933282.n4.nabble.com/FFMPEG-encoded-MPEG-2-video-causes-error-in-DVDAuthor-td2995983.html for details. The issue is summarized below:

The following command is used to encode videos in MPEG-2 (vob) format
for DVD authoring:

ffmpeg -i invideo.avi -target pal-dvd -f dvd outvideo.vob

('-target' can also be 'ntsc-dvd' or 'film-dvd')

Video streams encoded in this manner using the latest SVN will cause the
following error in DVDAuthor:

'ERR: SCR moves backwards, remultiplex input.'

DVD authoring then stops. Demuxing the streams and using them
individually, or remuxing them again, will make the error message
disappear, but the resulting MPEG-2 files (m2v or vob) or DVD are
problematic (choppy playback, no or wrong total playing time).

This issue appeared with SVN-r25383, when the following two lines were
added in libavformat/mpegenc.c:

1163 if(!s->last_scr)
1164 s->last_scr= dts;

The current source code has changed to:

The new code in mpegenc.c starting at line 1163 is now (but the issue still exists):

pts= pkt->pts;
dts= pkt->dts;

if(pts != AV_NOPTS_VALUE) pts += 2*preload;
if(dts != AV_NOPTS_VALUE){

if(!s->last_scr)

s->last_scr= dts + preload;

dts += 2*preload;

}

The error is shown in the below output from ffmpeg and dvdauthor:

See the ffmpeg and dvdauthor output below:

E:\Temp\bugfiles>ffmpeg -v 9 -loglevel 99 -i ranft.m2v -itsoffset -00:00:00.775
-i ranft.ac3 -vcodec copy -acodec copy -target ntsc-dvd -y ranft.mpg
ffmpeg version N-31653-gfaa3381, Copyright (c) 2000-2011 the FFmpeg developers

built on Jul 28 2011 01:57:12 with gcc 4.6.1
configuration: --enable-gpl --enable-version3 --enable-memalign-hack --enable-

runtime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libo
pencore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --
enable-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger

--enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx --enabl

e-libx264 --enable-libxavs --enable-libxvid --enable-zlib

libavutil 51. 11. 0 / 51. 11. 0
libavcodec 53. 9. 0 / 53. 9. 0
libavformat 53. 6. 0 / 53. 6. 0
libavdevice 53. 2. 0 / 53. 2. 0
libavfilter 2. 27. 3 / 2. 27. 3
libswscale 2. 0. 0 / 2. 0. 0
libpostproc 51. 2. 0 / 51. 2. 0

[mpegvideo @ 01F2B5C0] Format mpegvideo probed with size=32768 and score=51
[mpeg1video @ 02000260] Unsupported bit depth: 0
[mpegvideo @ 01F2B5C0] max_analyze_duration 5000000 reached at 5005000
[mpegvideo @ 01F2B5C0] Estimating duration from bitrate, this may be inaccurate
Input #0, mpegvideo, from 'ranft.m2v':

Duration: 00:00:08.88, bitrate: 8999 kb/s

Stream #0.0, 152, 1/1200000: Video: mpeg2video (Main), yuv420p, 720x480 [PAR

32:27 DAR 16:9], 1001/60000, 9000 kb/s, 29.97 fps, 29.97 tbr, 1200k tbn, 59.94

tbc
[ac3 @ 01F2F720] Format ac3 probed with size=8192 and score=51
[ac3 @ 01F297A0] Unsupported bit depth: 0
[ac3 @ 01F2F720] max_analyze_duration 5000000 reached at 5024000
[ac3 @ 01F2F720] Estimating duration from bitrate, this may be inaccurate
Input #1, ac3, from 'ranft.ac3':

Duration: 00:00:20.83, start: 0.000000, bitrate: 384 kb/s

Stream #1.0, 159, 1/90000: Audio: ac3, 48000 Hz, 5.1, s16, 384 kb/s

Output #0, dvd, to 'ranft.mpg':

Metadata:

encoder : Lavf53.6.0
Stream #0.0, 0, 1/90000: Video: mpeg2video, yuv420p, 720x480 [PAR 32:27 DAR

16:9], 1001/30000, q=2-31, 9000 kb/s, 90k tbn, 29.97 tbc

Stream #0.1, 0, 1/90000: Audio: ac3, 48000 Hz, 5.1, 384 kb/s

Stream mapping:

Stream #0.0 -> #0.0
Stream #1.0 -> #0.1

Press [q] to stop, ? for help
frame= 573 fps= 0 q=-1.0 Lsize= 10882kB time=00:00:19.11 bitrate=4662.6kbits
/s
video:9766kB audio:977kB global headers:0kB muxing overhead 1.301527%

E:\Temp\bugfiles>E:\Temp\bugfiles>dvdauthor.exe -o dvdtest -x dvd.xml
DVDAuthor::dvdauthor, version 0.6.18.
Build options: gnugetopt iconv freetype fribidi
Send bugs to <​dvdauthor-users@lists.sourceforge.net>

INFO: dvdauthor creating VTS
STAT: Picking VTS 01

STAT: Processing e:\temp\bugfiles\ranft.mpg...
ERR: SCR moves backwards, remultiplex input: 23131 < 8589910134

E:\Temp\bugfiles>

[johnnyquid]

zip file with input files and batch file to recreate the bug

[wg]

The issue is actually not with backward-moving scr but with negative or "wrapping" scr. Of course ffmpeg should not generate negative timestamps in mpeg output. But there is an easy workaround: Use "-muxpreload 0.775" to compensate for your negative -itsoffset. You will lose some packets due to buffer underflow but that is simply due to them being too much out of sync video vs. audio.

[johnnyquid]

I tried adding -muxpreload 0.775 to the ffmpeg command line but the error message from dvdauthor remains the same.