Acid Pro 9 - songs drift out of sync

Datorhead wrote on 2/6/2022, 3:31 AM

I'm having varying problems with syncing songs in Acid. I have versions 8 and 9, and I have occasionally had this problem in version 7 too, but it has become worse and occurs more frequently than before.

I'm making projects mimicking beatmixed DJ sets. The Transitions between songs drift gradually more and more out of sync. If I start playing right before a transition, the first one usually is rather fine, but as playback advances, the drift is more and more prominent in every consecutive transition. When zooming into the waveforms, the beats are visually in sync and the beatmapping should be correct.

Originally this only used to happen if both songs were timestretched/pitchbended, but at least not noticeably when at least one song was only re-pitched. Also it was sometimes made worse if I had MANY inactive tracks with songs overlapping the transition, or if Acid occasionally decided to use a non-ASIO audio device. Now neither of these resolutions seem to help at all.

Am I running out of computing power, or should I go through the trouble of reinstaling the system, or is it an audio device issue? Or might the 64 bit version solve this? I'm curently running the 32 bit version because I use an old VST plugin that has no 64 bit option. I am using Focusrite Scarlett 18i20 for the palyback device in Acid. One thing that I find weird is that when starting Acid, in the splash screen it seems to list a plethora of old audio devices that are no longer installed, including Traktor Audio which I haven't had for years, and which I don't remember installing into this system.

Comments

SP. wrote on 2/6/2022, 7:04 AM

@Datorhead Is there a difference in your recording sample rate and the sample rate of the program?

Datorhead wrote on 2/6/2022, 9:13 AM

As far as I can tell,

-the songs are mainly recorded at 44100 with a few 48000, and some "wild" rates, some 24, mostly 16 bits

-the project is set to 44100/16

-the Focusrite device setting is 44100

If there is a way to set Acid's own samplerate separately from these, I don't know where to do so.

Because Acid is still not very good at beatmapping, I have knocked the songs somewhat straight in Live so that mapping would be easier. The "wild" rates concern a few songs that are off pitch but have a straight beat pattern, so I have just set them a rate at which they play natively at the correct pitch.

So far I haven't noticed that different sample rates or bit depths of the songs would matter, and now that I have done some checks, it seems rather very sporadic. Appears that in my latest project the worst affected transition only has one pitch-bended song, and nothing else overlapping on passive tracks.

SP. wrote on 2/6/2022, 10:12 AM

@Datorhead Different sample rates are always a bad idea because they usually cause playback speed problems.

If you export the project as an audio file, does everything line up?

shkr wrote on 2/6/2022, 1:22 PM

hmmm... weird behaviour. Without seeing the actual project it is really hard to tell where the poblem is.

You must troubleshoot yourself. Here's what I would do:

As SP. wrote: check if this is a playback issue or it also happens in rendered file

I had a vst once that did not report latency properly, acid could not compensate it - see if this is the case by removing vsts used in the project (do it one by one to find possible offender).

convert all your songs to the same sample rate/bit depth. You can use whatever audio editor you prefer. Than set acid's sample rate/bitdepth to this value and prepare your project. Add tracks one by one and see if there's a particular audiofile that is causing desync.

Just some thoughts 

Datorhead wrote on 2/8/2022, 7:26 PM

Sorry for the delay of a couple days, I have been busy with other stuff.

The desync occurs in the rendered file just as well.

Appears I wrote a long comment in vain, and got kicked out while typing. Anyway, I record a lot of songs from vinyl, and for technical reasons concerning the original cutting process and the pivot tonearm at playback, they take some processing to come up with a straight beatmap. So I have used Live to knock the songs even somewhat straight, then adjust the playback tempo so that I can play a keyboard in tune along with the song, and then render the song in a file where it would play at a correct pitch at the native rate. For most songs this is very straightforward, while others can have such an irregular beat that they are almost frustrating to work with and require timestretching to keep the pitch from jumping all over the place between measures.

I must check the effects as well, and see if the same songs might behave differently when I move them elsewhere in the project, etc.

sheppo wrote on 2/20/2022, 9:53 AM

Are your source clips in MP3 format or some other lossy format? I ask, as I have seen this problem, especially with VBR MP3. It happens a lot less in AP10 for me.

That said, the workaround for me on earlier versions to convert MP3s that I want to use in my project, and exhibit this issue to WAV or FLAC.

Datorhead wrote on 3/7/2022, 1:03 PM

Are your source clips in MP3 format or some other lossy format? I ask, as I have seen this problem, especially with VBR MP3.

My source clips are in WAV format, and the same rate and depth. I have had mixed rates and depths and not noticed this desynchronisation very often. It doesn't seem to occur (or stay absent) consistently in any combination of configurations.

I know especially VBR MP3 can cause issues, I have had a car player where the time display went totally haywire with VBR, and trying to seek inside a song also gave totally random playback locations. That really sucks on a 2 hour DJ mixtape.

Datorhead wrote on 3/16/2022, 3:35 PM

I think I have a partial solution. The pitch bend/time stretch mode used seems to affect this at least a little bit. If I use élastique (either pro or efficient) and set a pitch shift at a non-native tempo, the drift is worse than with, say, classic/music6. Only in Acid Pro 7 the élastique mode didn't seem to have this effect.