On Sunday 22 January 2006 11:50, Andrew Stevens wrote: > Hi Bob, > > > > 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? > > Actually, I just heard from Steven that he may have encountered the issue > himself. Could be a bug in the AC3 reading code that (e.g.) does bad > things if bit-rate changes in mid-stream or something like that. > > > > 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? > > Unix/linux has a nice collection of general-purpose file-processing tools. > There's one called 'head' that allows you to copy the first so-and-so many > bytes of file. > > > head --bytes=<point I want to chop file off> at original_file > > chopped_version > > In your case: > > head --bytes=349129984 orginal.ac3 > chopped.ac3 > > There is of course a corresponding 'tail' that allows you to copy the bytes > after byte so-and-so or the last so-and-so bytes of a file. > > Combine with 'cat' (which outputs the result of chaining together various > files) and a little imagination and lots of useful things can be done. > > > > Other things to try: > > > > > > - Try re-extracting the AC3. > > > > Did that twice, with two different DVDs. same result > > Hmmm... that makes a systematic error either in the extraction or in mplex > parsing software 99.9% likely to be the problem.
That could be the answer/problem. Like I said in my early post. This worked flawlessly for me until I upgraded my packages. > Can you run a few quick > tests for me to see if we can isolate the problem? Yes, absolutely. Appreciate help and guidance. > > I need to know how long the original AC3 file was... movie.ac3 is 403106816b (384.4mb) > > What happens if you mplex with the a some AC3 taken off the front of the > sequence > > run > > tail --bytes=+179200 your_original.ac3 > shifted.ac3 tail? or head? Ran your tail command and it produced a shifted.ac3 file of 23568384b (24 mb? - pretty drastic) > > and then 'mplex' with 'shifted.ac3' instead of your original .ac3 file. OK did that and got this response: EasyStreet:/workspace # mplex -f 8 -o "movie.mpg" shrink.m2v shifted.ac3 INFO: [mplex] mplex version 1.8.0 (2.2.4 $Date: 2005/08/28 17:50:54 $) INFO: [mplex] File shrink.m2v looks like an MPEG Video stream. **ERROR: [mplex] File shifted.ac3 unrecogniseable! **ERROR: [mplex] Unrecogniseable file(s)... exiting. EasyStreet:/workspace # > > If you've got the disk-space spare pls. don't discard the .ac3 - if it > looks like an mplex problem it would be super-useful to be able to email me > the critical section where things go wrong to debug mplex. No, I have the space. Will keep it until this problem is solved, hopefully. Also have the space to reproduce the ac3 file from the other DVD that is failing if necessary. 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&kid=103432&bid=230486&dat=121642 _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
