Am I asking for sync problems?

[Karl Engel]

A friend's asked if I can clean up the audio of a DVD - audio production is what I do but getting it back onto the DVD in sync had me concerned. Checked all the Tools, not allowed to spend $ on TMPGEnc (and a previous trial means it isn't free), so was chuffed to find I could do it all for nix apparently: can extract the audio as .wav, denoise/eq/enhance & export as MP3 with my existing audio programs, extract the vision as m2v with VOBrator, then multiplex (is this the same as remux?) with ImagoMPEG Muxer. Did a short test, all seemed to work. But is this likely to be out of sync by the end of a 1,048,404 KB .vob file?

Also, as I don't have AAC tools, are there any guidelines for generally used MP3 bitrates on DVDs? I know it's all about tradeoffs and in sound production I regard 128 as the absolute acceptable minimum (and then begrudgingly!).

The source material is on VHS and if I get access to the original, which I'm told runs "probably more than an hour", I'll be doing the juggling act to keep it all on one (single layer) DVD and looking as good as possible with the encoding software I have (MyDVD 4.5. You can stop laughing now.) My understanding is this uses UNcompressed audio so by turning the audio into an MP3 I might be able to get it all into one DVD using the Best setting - 8mbs - which I've always been happy with)

Not allowed to spend a cent on this! If it's unlikely my approach will work I'll send her off to a professional.

[redwudz]

MP3? What for? Are you making a Divx? If it's a regular DVD, skip the MP3 part and convert the filtered WAV audio to AC3 with ffmpeggui. It's free. Then put that back in when you author.

mux=multiplex demux=demultiplex

As long as you don't alter the length of the audio or the video, they should stay in sync. But you can check it before your burn to DVD.

You could also use VOB2MPEG to take out the mpegs, then use the authoring program to assemble the audio and video and create the DVD format. No muxing required. DVDAuthorgui can do it for free if you don't need anything fancy. You will have a lot less problems with audio if you just use the authoring program to join the audio and video.

[Karl Engel]

Thanks for the suggestions. Didn't realise MP3 wasn't supported by the DVD specs, just discovered this in a search of this forum. A bit surprised then that MP3s will mux into a .vob and play fine on the computer.

Sorry I don't follow how I can avoid muxing. After working on the audio I will have new AC3 files the length of each VOB and the m2vs which I gather are just the video component of the original VOBs. If I use VOB2MPEG those MPEGS will contain the old audio, won't they? Are you suggesting I demux those MPEGS instead? I see VOBrator will demux an MPEG if it's renamed with a .vob extension. The DVDAuthorgui site links to BatchDemux 0.14 which might be a better tool. I don't have tools to extract .wavs from MPEGS though, only true VOBs, and the ones I see available all cost $...

I'll have a look at DVDAuthorgui tomorrow - sounds good if it lets you assemble the audio separately from the vision

[dphirschler]

You will need to get a grip on these key points:

1) rip the DVD

2) demux the audio and video.

3) edit the audio

4) convert audio to AC3

5) author the DVD.


If you are ripping from DVD, then you will not have to encode any video. However, if you get ahold of that VHS tape, then you will of course have the additional steps of capturing, minor video edit/restoration, and encoding.


Darryl

[greymalkin]

As long as you use the audio/video from the dvd and don't do any stretching/adding silence/etc. to the audio it will stay the exact same length and you won't have sync issues to worry about.

a few things I think you might still be confused about.

When you author the dvd you get to pick which video stream and which audio stream you want for each track. So you
1 - Rip the dvd. You now have the video&audio stream
2 - demux to give you the audio stream by itself.
3 - assuming it's ac3 audio stream..convert to .wav and edit.
4 - re-encode to ac3.
5 - when you author..you will just point to the video stream and then point to the NEW audio stream. The authoring program will mux them for you.


You also mentioned being able to get the original VHS. If you do this you would be best to re-capture the audio and video rather than just trying to get the audio from the VHS and the video from the dvd. The reason I say this is that you will have a very high probability of sync issues this way as the motor in your vcr or just any number of variables could cause the vhs tape to track slower or faster than the time it was captured to the DVD. This will cause a sloooow steady drift out of sync which will be a pain to fix. So either work with the audio already on dvd, or if you do vhs I would re-capture the whole thing. In other words, unless the audio is bad on the dvd i wouldn't even mess with the vhs.

[jman98]

Karl, forgive my bluntness as I not trying to offend you, but I'm a little troubled by your questions. Since you thought that MP3 audio was OK for DVD (and please note that MP3 is NOT the same as MPEG-1 layer 2 audio which can be valid for PAL DVD), I just get the feeling that you misunderstand this whole process at such a fundamental level that I'm not sure you should be doing this until you have learned a lot more about what you want to do.

Is it likely to be out of sync? Well, it shouldn't be if you know what you are doing. A better question for you is whether your friend is very cheap and just wants it done and will live with you doing it in a maybe less than ideal way or if your friend is going to be angry because you didn't do something right. If you think there is a good chance for the latter, I'd suggest you pass on this job until you're more sure about what you actually have to do.

Speaking of MPEG audio for DVD, you should realize that MPEG-1 layer II audio is valid only for PAL DVDs and at least one of LPCM or AC3 audio must also be present on the DVD. You should also realize that after you go to all this trouble that your friend could still have problems with the final result, even if you do everything correctly. Your friend might not be able to play the disc you burn it to as some older players don't like burnable media or might not like the particular brand you are using. If you do this, you'll learn a lot, but you'll have to decide how fussy your friend is and if this is really important to him or her, I think you might want to pass on this until you're a bit more experienced.

[redwudz]

This is how I would filter the sound on a DVD. I'm sure there are better tools, and probably better methods, but these have worked for me.

I use DVD Decrypter in File mode to rip the DVD. In the File Mode settings, I set File Splitting to None. That gives me one large VOB of the entire DVD. I use VOB2MPEG to convert to MPEG. (I think you can skip the DVD Decrypter step with this program, though I haven't tried this.) I use VirtualDub Mod to take out the WAV. I filter in Audacity and save the new WAV. I convert the WAV to AC3 with ffmpeggui. So far, this is all freeware programs. I put the MPEG into TMPGEnc DVD Author. I select the new MPEG in TDA and the new AC3. Add chapters, menus, etc. in TDA, author and burn. You should be able to do the authoring step in DVDAuthorgui, though I don't use the program.

I do this with AVI files all the time. Instead of ripping the DVD, I encode the AVI to MPEG-2 then process from there.

For me, this keeps from having to deal with the individual VOBs in a DVD. Once I have the DVD converted to one MPEG file and have converted the edited audio to AC3, then I just process it like any other MPEG/audio file with the authoring program. Reauthoring it is easy at this point. Just add the MPEG and the AC3, make menus and chapters, author and burn.

[greymalkin]

jman,

i hope someone was just as condescending to you when you decided to start. You don't know what this guy knows. He has already said he is good with audio editing...which tells us he's technically able to grasp certain concepts. His friend wanted him to do the editing, probably because he's good with audio editing but it's really none of our business why. Pointing out "AC3 instead of MP3" and a few basics about dvd authoring is all he needs. Not some lecture about how disturbing his ignorance of this facet of dvd creation is. His experience is with the editing of the audio, and he just needs to know what to do after that. He doesn't need to hear any "I read a book" trivia about dvd creation unless he asks for it.

[Karl Engel]

Thanks again for all suggestions, and the time you've taken to explain things. The most you can know is how little you know.

The only authoring program I'd used was the very basic MyDVD 4.5 that came with my burner, which doesn't let you point to a different audio stream, so I wasn't familiar with that process.

I've learnt most of what I know through reading here and just trying stuff with the basic tools I had to see what happens. I tried muxing an m2v with an MP3 into a VOB and since it worked & played back (on the computer), I incorrectly assumed this format was supported. Of course I know better now.

I hadn't noticed the option to set file splitting to none in DVD decrypter, so that's a good suggestion. If I get this on DVD I wouldn't otherwise have put it through Decrypter since it will have been made from the original (somewhat precious) VHS domestically by the owner, and I will take great interest in what process she uses to do this, as I'm aware this is where the first potential quality drop may occur.

If I get the option of making the DVD from the original VHS myself, I wouldn't have had a DVD already to rip the audio from, and there's no way I would consider muxing pictures and audio from different sources in any case. My original post was concerned about potential sync drift just from working with & re-encoding the original audio! Sorry if my post was ambiguous.

I'll have to move on to some other (paying) jobs now so won't try it all out until it comes to fruition, at which time I might add to this thread. Do threads go "dead" (can't be added to) after a period of time?

[redwudz]

Threads drift on down and are harder to find, but you can save a shortcut to it. They are not deleted. I believe my very first post is still in the server and available. And that was more than 5000 posts ago.

Kind of scarey.

Best advice is to read the guides that are on this site. There's a lot of good information available there. And if you get stuck, just ask.

[Nelson37]

Since you are experienced in doing audio, I would NOT start over with the VHS, this adds a whole slew of issues in addition to just re-encoding the video. If you must, get something besides Sonic for an encoder. Anything, anything at all, just not Sonic.

MyDVD is OK for simple authoring, it will accept an AC3 file if it is already muxed with the video. MP2 it will convert to LPCM.

On the muxing confusion - most authoring progs want DeMuxed audio and video, which the authoring prog will then mux into VOB files. So, yes they must ultimately be muxed together, just that you do not have to do it.