Problem Splitting MPEG and rejoining with mplex

[jon111]

Having problems creating MPEGs for use with dvdauthor. Any help greatfully received....

Have tried two mechanisms for splitting MPEGs taken from DVD recordings into m2v & ac3 (Dobly Digital 2.0 256). (Both avoid re-rendering, just split the data out, though am happy to try others.)

MPEG_StreamClip gives a perfect m2v file, but the ac3 file for most is either a small section, or noise (twice the length of a working file).

DGIndex gives perfect m2v & ac3 files, but mplex (windows version 1.9.0 (2.2.7)) fails with

**ERROR: [mplex.exe] Can't find next AC3 frame: @ 24576 we have 4814 - broken bit-stream?

command line is:

mplex.exe -v 1 -f 8 -o 10-Nov-01_The Giant Whirlpool.mpg 10-Nov-01_The Giant Whirlpool.m2v 10-Nov-01_The Giant Whirlpool.ac3

and AC3 info is:

INFO: [mplex.exe] AC3 frame size = 1024
INFO: [mplex.exe] AC3 AUDIO STREAM:
INFO: [mplex.exe] Bit rate : 32768 bytes/sec (256 kbit/sec)
INFO: [mplex.exe] Frequency : 48000 Hz
INFO: [mplex.exe] SYSTEMS/PROGRAM stream:
INFO: [mplex.exe] rough-guess multiplexed stream data rate : 1864800
INFO: [mplex.exe] target data-rate specified : 10080000
INFO: [mplex.exe] Setting specified specified data rate: 10080000
INFO: [mplex.exe] Run-in delay = 10800 Video delay = 10800 Audio delay = 2160
INFO: [mplex.exe] New sequence commences...
INFO: [mplex.exe] Video e0: buf= 0 frame=000000 sector=00000000
INFO: [mplex.exe] Audio bd: buf= 0 frame=000000 sector=00000000

Any ideas where to start debugging? Thanks for any help!

[Baldrick]

Try "fix" the ac3 with ac3fix. Or try demux the dvd with pgcdemux.

[AlanHK]

Also fix AC3 using BeSliced included in http://dspguru.notrace.dk/BeSplitv0.9b8.zip

[jon111]

Thanks for the help. Using the ac3 file from DGIndex:

ac3fix creates a file which works with mplex, but is out of sync with the video.

[output:
Frame length is 1024
Checking frame 25: Wrong frame length, expected 23552, got 1024
Writing frame
Current wrongness is 200 bytes
Checking frame 20635: OK
Finished. Found bad frames. Final wrongness is 200 bytes]

beSplit (though I only used a simplistic -input/-output/-type/-fix) produces a file 10% of the size, which is just noise.

pgcdemux sadly can't help, as I'm starting from MPEGs ripped from a DVD-VR.

[if it helps, the aim is to take the existing MPGs and hand them to dvdauthor - the only way I've seen so far is to split video & audio, then recombine with mplex leaving space for dvdauthor information. Worked for those taken from DVD-VRs from a Sony, not not these from a Toshiba]

Any more ideas gratefully appreciated.

[AlanHK]

Thanks for the help. Using the ac3 file from DGIndex:

ac3fix creates a file which works with mplex, but is out of sync with the video.

A constant offset?
Use Delaycut.
Actually, just saving an AC3 via Delaycut with no delay applied should clean up the format.

[jon111]

Thanks! I tried Delaycut, and it found the same break in the stream:

====== PROCESSING LOG ======================
Time 00:00:00.736; Frame#= 24. Crc2 error FIXED: read = C1B4; calculated=94BD
Time 00:00:00.768; Frame#= 25. Unsynchronized frame...REWINDED 200 bytes. Found new synch word

but when recombined, the audio was again behind the video.

So, I think that the delay may not be due to the broken ac3 stream, and may be just something I need to add into mplex. The DGIndex ac3 filename shows "DELAY -352ms" - so I tried adding "-O 352ms" into mplex, and that seems much better (I can't prove its totally accurate).

I'm interested in the technical info behind this delay (why it occurs, and how to recognise it in an mpeg file if I didn't use DGIndex for splitting). Any further info greatfully appreciated.

[AlanHK]

Another program you can try for demuxing is Rejig. It has an option to "correct AC3 delay" while doing so.

Of course, Delaycut can also add the delay into an AC3 file if you know what it is, that's its raison d'etre.