On Saturday 21 January 2006 05:41, Andrew Stevens wrote: > 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! > > > 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.
OK, I think. > > 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. OK. > > 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. Ummm...Not likely, right? > > 2. The AC3 stream is corrupt. Could be, I guess. More below. > > 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). Woooo... OK, I think I know what you are saying. But certainly don't know what to do about that. How does one "chop off" a couple of kb? > > Other things to try: > > - Try re-extracting the AC3. Did that twice, with two different DVDs. same result > - 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. I have no idea how I would do that. Have seen others talk about this but wouldn't even know where to start or what to put there once I did. > > - 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). Wow.. Modify source code........No, may not be rocket science, but isn't calculus/logic 101 either. Way over my head. I would have to understand what it is that I am looking at/doing, and that is beyond my mere mortal capabilities at this time. > How about this, I muddle along trying the various things that I understand/ are capable of doing, and report back hoping that benevolent gurus like yourself have the patience to guide me along the proper path. Mind you, I am not seeking a tutorial on this. Just some guidance on what to do next or where to find it, I am an old guy (70 yoa) There were no computers when I was a young man, except maybe that IBM behemoth with vacuum tubes. I started out with DOS and Win 3.11 many years ago (15+ ?). Have no formal training whatsoever. Started with Linux RH 5.something 5(?) years ago? I have little desire nor the time to explore the depths of DVD authoring/conversion. Just fascinated by it and trying to reproduce usable DVDs for my grandchildren. (Charlotte's Web etc. ?) Anyway, I really appreciate your reply which gives me better understanding but not necessarily solutions to these things. Thanks again, Bob S. ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://sel.as-us.falkag.net/sel?cmd=lnk&kid3432&bid#0486&dat1642 _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
