Hi,
> Joined this and the transcode list about a week ago and have been lurking
> to see if I am in the right place....
You're in the right place for mplex!
>
> Sent a very similar message to the transcode list and they provided a few
> suggestions which did not work out. They told me this is where the mplex
> experts hang out, so here I am.
>
> Anyway, I can still build my vob's separate my audio and video, and shrink
> my video using tc. Problem comes when I try to rebuild the files to an mpeg
> with mplex using the command; "mplex -f 8 -o "movie%d.mpg" shrink.m2v
> movie.ac3" The command errors out with the following. Here are some lines
> from the first try:
> **ERROR: [mplex] Can't find next AC3 frame: @ 349129984 we have 04c3 -
> broken bit-stream?
> linux:/workspace #
AC3 audio frames have a header that starts with a 16-bit byte-aligned
'syncword' 0x0b77 and includes a encoded frame-length.
This error message is generated if, when mplex tries to read the next AC3
frame it does not find the sync word. The hex printed out after 'we have' is
what it found in place of the syncword.
There are really only two possible causes.
1. There is a bug in mplex' look-up table that gives the length of AC3 frames
from the encoded frame-length.
2. The AC3 stream is corrupt.
Mplex reckons it at byte 349129984 in the AC3 stream. Now 448 kbit/sec
corresponds to a mere 56000 bytes per second. So mplex reckons it is 103
minutes into the audio stream. If this is very near or at the end of the
video stream the probable cause is simple: something upstream truncated /
corrupted the last AC3 frame. Simply chopping of 1-2KB from the end of the
stream should solve your problem (mplex can recover from the last frame being
chopped off).
Other things to try:
- Try re-extracting the AC3.
- Use a hex-editor to patch the AC3 stream. The frames appear to be all 1792
bytes long. Copy the bytes from 349129984-1792 to 349129984-1 incluse to
349129984 to 349129984+1791 inclusive. You'll get a 'pop' in the audio but
mplex should be able to recover.
- Grab the source code and modify the AC3 reader loop so it simply ignores
some number of broken CRC's and just extrapolates from previous AC3 frames
instead of giving up immediately. Not rocket-science (see
mplex/ac3stream.cpp - its obvious whats going on).
cheers,
Andrew
>
> On my last attempt, I got this:
>
> INFO: [mplex] target data-rate specified : 10080000
> ++ WARN: [mplex] Target data rate lower than computed requirement!
> ++ WARN: [mplex] N.b. a 20% or so discrepancy in variable bit-rate
> ++ WARN: [mplex] streams is common and harmless provided no time-outs will
> occur
> INFO: [mplex] Run-in Sectors = 89 Video delay = 13019 Audio delay =
> 16022 INFO: [mplex] New sequence commences...
> INFO: [mplex] Video e0: buf= 0 frame=000000 sector=00000000
> INFO: [mplex] Audio bd: buf= 0 frame=000000 sector=00000000
> ++ WARN: [mplex] Stream e0: data will arrive too late sent(SCR)=102253
> required(DTS)=13019
> ++ WARN: [mplex] Video e0: buf= 32875 frame=000061 sector=00000037
> ++ WARN: [mplex] Audio bd: buf= 14781 frame=000038 sector=00000034
>
> From those warnings I am guessing that somehow the audio & video are out of
> sync. (bitrate?) but I just don't know, or if so, how to fix it. Nothing in
> man mplex jumps out at me.
>
> More info: I deleted everything and tried again. Same result. Then I tried
> a different DVD ( that I had copied successfully before) and got the same
> result.
>
> I have google-d, howto-ed man-ed and faq-ed for hours on end without
> finding the answer. The most helpful was LinuxQuestions but even there,
> although the problem was brought up, there were no answers.
>
> Really hope this is the right place and that somebody can help me. As I
> said before, I never had any problems in SuSE 9.2 with the older versions
> of this software.
>
> Bob S.
>
>
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