DIY DVD Commentary

August 18, 2006 7:43 PM

Help me create my own commentary track for a DVD movie.

So I've got a DVD movie (ie: VOBs and whatnot) on my hard drive. I have an mp3 audio track with commentary. I need to do this:

1) Extract the audio track from the movie.
2) Composite that track with the commentary track to produce an audio track that is the commentary over the movie audio.
3) Add this new track to the dvd.

I have Nero SoundTrax, and as far as I know that should help me accomplish #2. If anyone has an easier or better solution, please do let me know.

I'm sure this is pretty simple, but I have never authored a DVD before.

posted by crypticgeek to Computers & Internet (6 answers total)

Response by poster: I guess I should mention also that it's a 5.1 track. I suppose this means I need to rip out the AC3 audio without converting it, overlay the mp3 on to the center channel, and then write an AC3 back out? Guess SoundTrax is out, as I don't think it can write AC3. Is there another 5.1 format? It has 5.1 mixing, so I ssume there must be otherwise why have it if it can't write out a 5.1 file.
posted by crypticgeek at 7:54 PM on August 18, 2006

You could try something like Sharecrow.
posted by robbie01 at 8:01 PM on August 18, 2006

Response by poster: That looks like a cool app robbie01, but it has no way of burning it off. You can't even export the crow file for someone else to play in sharecrow on thier machine as they haven't finished that feature yet.
posted by crypticgeek at 8:10 PM on August 18, 2006

I think typically the commentary track is 2 channels, because that's the lowest common denominator. You shouldn't assume the person watching the movie even has a center channel speaker.
posted by knave at 9:29 PM on August 18, 2006

Response by poster: Shouldn't people who only have stero have their dvd player setup for such. Don't dvd players down mix to stereo if set that way?
posted by crypticgeek at 12:55 AM on August 19, 2006

Best answer: If they know what they're doing, yes. (Most people don't, but that's a whole 'nother discussion...). But if you check out commercial DVDs, you'll find almost all commentary tracks are 2-channel only. So, you might as well stick with stereo.

As for the original question : I'm doing exactly this at the moment with a couple of DVB-T sourced programs, and audio commentaries off the 'net (thank you, BBC ;-). Since the commentaries I get are lowish-bitrate mono MP3, I convert both the commentary & original to WAV @ 48k sample rate. Then I take the commentary, add a _little_ bit of stereo reverb to liven it up, then use trial-and-error to sync with the original audio.

At that stage, I reduce the level of the original audio track (so it sits in the background of the commentary), mixdown to a single stereo audio track, then save it as MP2 (I'm in PAL-land; in NTSC-land you'll probably want to convert to 2-ch AC3).

I do all this in Cool Edit Pro, and the hardest part is synching the commentary track to the action - I'm doing it partly by ear against the original audio, starting with an initial educated guess as to any offset. Mostly I view the waveforms in multitrack mode, looking for pauses in the commentary - usually, some important event is happening on-screen during those breaks, and the commentary makes note of it when it resumes.

As for the final step : well, how well do you understand the DVD structure? Easiest way it to just re-author it in whatever you use (DVDLab Pro for me, because I'm starting with plain DVB-T-sourced demuxed MPEG). Stand-alone VOB muxing tools (to add the new stream to the VOB) + IFOedit (to add the additional stream info to the IFO "header" files) could be used with a pre-existing DVD structure.
posted by Pinback at 3:57 AM on August 19, 2006