How do i extract the audio from a Divx movie...

[scarface]

Hi my first post here! I got 2 questions. 1) I got a bad quality copy of a movie in divx. I got a dvd of the same movie but in only one foreign language. Is it possible to extract the audio from the divx and then mux it with a new conversion(divx)?? 2) Everyone is talking about the R9 codec. I did see a comparison guide of all the codecs in here somewhere(I cant seem to find it anymore. Where can I get this codec and how do I convert with it? I am willing to get the Helix Producer software to do if its the right software. Thanks in advance for any help ;)

[jggimi]

Welcome to the forum. I can answer the first question.Is it possible to extract the audio from the divx and then mux it with a new conversion... If the audio track matches up exactly -- they may not, as one may have been from PAL and the other from NTSC, and these often have different timing -- then yes, you can do this. I recommend you start by gaining proficiency with encoding tools. For DivX encodings, the most popular encoding suite among Doom9 users seems to be Gordian Knot. I recommend you start with Doom9's DivX guides, and follow them step by step several times before branching out into such a non-standard activity.

Here are the steps I would take to do this sort of thing.[list=1] Run Gspot against the .avi file, confirming the length, codec and format of the audio stream I want to extract from it.
Extract the audio stream from the existing DivX .avi using Nandub's Save WAV command, saving the file with the appropriate filetype (.ac3, .mp3, and the like).
Use that audio file as input to the Audio A section of the Bitrate tab on Gordian Knot
Select the audio file in the Audio 1 tab of the Add Job window on the Encoder tab
If the audio is in sync, I'm done (very doubtful).
Use Nandub, rebuilding the .avi with different delay values, until the starting audio appears to be in sync.
Check to make sure the audio is *still* in sync at the end of the content.[/list=1]Nandub is included with the Gordian Knot encoding suite, Gspot must be downloaded separately. You'll find guides to Gordian Knot in the DivX guides at www.doom9.org -- I wish you luck!

[scarface]

Thanks for the tips man! The dvd im ripping from is Pal and the Divx is NTSC:( Ill try it anyway using your tips with nandub to see if i can get it right. I really love this movie so if it dont work ill just go out and buy the original.

[jggimi]

It will probably not work. Both the PAL and NTSC discs may have been sourced from the same material, but the encodings are likely of different lengths, so the sound will not sync all the way through. There may be audio tools available to modify the audio track, but I'm not familiar with any.

Assume that both the PAL and NTSC versions came from the same source -- a 35mm film designed to run at 24 frames per second (fps).

For PAL, the usual transfer method is to speed the film up to 25fps. Audio gets "adjusted" to sound natural, even though everything is running 4% faster.

NTSC video gets Telecined -- this is a process whereby the film is first slowed down to 23.976 frames per second, then individual Frames are decoded into two Fields -- one with the odd lines and one with the even lines of resolution -- and then 6 additional frames are created each second by using fields from adjacent frames.

For NTSC DVDs, though, it varies...usually when the video stream is created from film sources, to save disc space, the Telecining is actually done by the DVD player, and flags in the video stream tell the player when to do it. When you read through Doom9's Gordian Knot guide, you will see a place where "Force FILM" is discussed. This is telling one of the tools in the suite to extract the full video frames from the video stream. You'll also see "inverse Telecine" or "IVTC" discussed. This is when a film source was Telecined (or partially Telecined) onto the DVD disc, and you must therefore decode the Telecined video stream to reassemble the proper 23.976 frames each second as part of the DivX encoding process.

Whew!

[scarface]

Wow Jggimi thats a hellova way to give me some bad news :D Thanks for the very thourough explaination! You da man!