Midi to WAV - Synchronization concern

C

Cazzbar

Throbbing Member
Hi there... this scenrio has been worrying me for some time

I have a piano midi track and a drum midi track. I need to convert each into wav file.

For this I will use my piano sound module and a separate drum sound module.

I will run my sequencer twice, the first time to create the piano wav (drum track muted) and second time to create the drum wav (piano track muted).

I now have my two separate wav files which I can play together.

Success you may say, but how can I be sure that those two wav files are 100% synchronized?

Have I just got to trust that my PC will always play back each midi track at exactly the same rate... as I fear if my PC glitched slightly whilst playing back one of those tracks the final two wav files would be out of sync.

Can someone please ease my mind on this, or tell me a way to guarantee the two wav files will be in sync.

Cheers
 
If you're also recording with your sequencer, it will do the alignment. If you're recording into something separate, like Sound Forge, it's a legitimate issue. You might want to start with a simultaneous hit on each track, so you can visually line up the tracks' starting points. You can also do an end-of-track hit on each track, and see how they line up. Sound Forge does some time stretching too, so if they drift, you can readjust...

Daf
 
You're the one who knows it :D

I mean, they should be lined up by theory. But there's another factor you'll want to consider... Soundcard !!!

Why would I need to consider it, Jaymz ?

Because of latency issue... I often found this case (specially on large amount of MIDI tracked song). I get somehow out of sync after converting >16 MIDI tracks to audio. It's very small, but catch my ears.

Older (or cheap) card will give you bad time on syncing the audio tracks, because of their poor driver architecture :) If you're not sure with your soundcard & application run, just use your ears... If you feel fine, then it's fine... if it doesn't, guess you know what time is that :D

;)
Jaymz

ps. What's your sequencer for doing MIDI & multitracking audio ?


...please consider Pre-ordering Homerecording.Comp CD's Vol 2 :)
 
Thanks guys, I'm glad you understand my concern. I have quite a high spec machine-- P3 766mhz, 256M memory, Aardvark Direct Pro Soundcard and Cubase sequencer.

Sometimes when I play my two wav files back together it sounds fine, other times I'm sure they're not sync'ed.

The fact that you can look at a graph of the wav files and prove that they end together doesn't mean to say they didn't separate somewhere in the middle. And why should you have to look at graphs anyway?

The process of recording wav files separately seems fundamentally flawed, yet it appears "that's the way it's done".

Are we all trusting to faith that our wav files are sync'ed? My computer is not a stranger to little housekeeping tasks which could slightly effect the playing and recording of tracks.

Please stay with me on this one as I can't find this topic discussed anywhere else.

Thanks,
Cazz
 
dafduc- I'm playing my midi tracks using Cubase, through a sound module, into my Direct Pro and recording the wav using Samplitude.

You mentioned "time stretching" if things go wrong, are you saying you cannot prevent things from going wrong using this technique? :(
 
Interesting discussion. I ran it to a sync problem for the first time a few weeks ago. It was also the first time I tried running 24+ MIDI tracks. Here's some info I found.

http://www.sweetwater.com/insync/word.php?find=MTS-MOTU

and

From a Digidesign review: MIDI Time Stamping (MTS) support provides sample-accurate MIDI with Pro Tools-compatible software synths and samplers, eliminating the possibility of compromised sync and drift issues. Also, you can take advantage of up to sub-millisecond-accurate MIDI with Digidesign's MIDI I/O and other supported MTS-capable interfaces.

All the major companies seem to have some sort of this type of technology, all way under 1 ms. My interface is no where near that accurate, but like I said I've never had any issues until I went to 24 tracks.

Stray
 
Why are you obsessing over a fix for a problem you don't have? Of course midi sync works or it would be worthless. There have been reliable ways of syncing up mechanical decks for 30yrs and compared to that digital and midi sync is easy. I am not saying it is perfect but just do it and then if you have problems you can fix them.
 
I think I do have a sync problem, if only slight, and the fact I'm not doing anything to prevent it concerns me.

I feel I need to look into MTC to link my sequencer and recording software.

Maybe if I had one program to perform sequencing and recording this would not be an issue. hmmm...
 
I've never needed any fancy sync when dumping even 32 tracks of MIDI (2 ports worth) into an auidio program a track at a time.
I've only seen the MIDI interface crap out from event overload a few times, and I program a lot of high density event stuff.

The MIDI playback is pretty damn consistent from play to play. I use an ancient parallel port MusicQuest 2Port/SE connected to a PII-450 running Cakewalk. I output the synth left right pair to a Delta 1010 in a P4 system all at once or one at a time. If I need to line them up later and I can't do it by waveform inspection, then I apply a notch to the beginning of each imported file at the same realtime playback position. A cinch to line up the file in the multitracker at that point. Easily done in the MIDI sequencer by adding a hit of something percussive in each track prior to measure one.
 
I've looked at all the sync options and it looks like a level of complexity I could do without... if the Dr says his 32 wav files are consistent then I'm going to have to check out my PC.

Yesterday I thought I'd put my band's rough cassette tape on CD for convenience, but playing it back there's a bit where it jumps back a second, just like a needle on an old 45! I checked the original wav and it's on there as well (and there's no problem with the cassette)

I've just run msconfig and found out my PC's running a huge bag of processes on start up that I'm sure I don't need... something which looks like a PC Doctor is first for the chop!

Thanks all
 
Here's a link with some info on how you can further optimize Windows for audio.

http://www.tascam.com/support/faq/pc_optimize/index.php

BTW, I think I should have read your initial post better. My sync problem was at the start point of the last 4 of 28 tracks. Meaning tracks 25 - 28 started a few ms later than the first 24. This was easily remedied by lining up the waveforms, but I felt that to be not very precise so I found MTS as a possible solution.

I realize now that doesn't really address what you were talking about. Sorry for any confusion.

Stray
 
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