Wav files recorded on separate devices not aligning in Live

[tigali]

Recorded an interview with two mics going into a Zoom hard disc recorder and one mic recording into Ableton Live. I'm now editing the interview down and the file recorded into Ableton seems to be running at a slightly different speed. After every (roughly) 2 minutes the audio starts to audibly separate causing a phasing and then echoing sound. I'm having to manually match the audio files up every couple of minutes, which is a huge PITA.
Anybody know what might be causing it? The file was unwarped before being exported from Ableton Live. I then dragged it and the Zoom Wav files into a new Ableton Live project.
Could dither be the issue?
Any help much appreciated

[Tarekith]

Definitely not a dither issue.

When you dragged the files into a new project, did you make sure that they also had warping turned off?

[tigali]

Thanks for the reply Tarekith.
Yes, no warping in the new project. All the files are unwarped and untouched, yet the Ableton recorded file seems to move at a very slightly quicker pace than the Zoom recorded tracks (no pitch difference as the files are of the one conversation so I can hear the spill from the other mics on both recordings).
Could it be to do with recording settings? Bit depth? Is there anything there that could cause this?

[Tarekith]

Not a bit depth issue, but are the files all the same sample rate?

[tigali]

Hmmm... that I do not know. I will have a look at the Zoom and see what it is set at. I'm assuming my friend who recorded into Ableton has left it at the default settings so possible 16bit but I will ask him. Could that cause the kind of issue I'm talking about?

[Tarekith]

16bit is the bit depth, not the sample rate which would be 44.1kHz, 96kHz, etc. If the files are a different sample rate, Live will convert them to your project sample rate but that could “possibly” lead to tiny timing differences over the coarse of the song.

[Shift Gorden]

I don't have a solution for the OP but I can confirm I've had a similar issue before. I recorded a couple of tracks on my Tascam, and in Ableton. After a minute or so, the tracks would slowly drift apart.

I never figured it out...but I never had the problem again either.

[jestermgee]

The issue is to do with the fact that even if BOTH recorders are set to the same frequency/bitrate the clocks that drive each one separately are not 100% accurate so there will be a small difference in the speed just the same as if you record to 2 separate tape decks. After playback at some point the time will drift and the signals go out of sync.

Hence the reason timecode exists for syncing multiple sources to an accurate clock.

There is software that can align the signals (google around) and another method is to use a clapper at the start and end of your recordings and use that spike to quickly line up the start and ends. If you can quickly align the ends and starts they should fall in line but you will have to stretch one of the sound files slightly.

[Shift Gorden]

The issue is to do with the fact that even if BOTH recorders are set to the same frequency/bitrate the clocks that drive each one separately are not 100% accurate so there will be a small difference in the speed just the same as if you record to 2 separate tape decks. After playback at some point the time will drift and the signals go out of sync.

Hence the reason timecode exists for syncing multiple sources to an accurate clock.

There is software that can align the signals (google around) and another method is to use a clapper at the start and end of your recordings and use that spike to quickly line up the start and ends. If you can quickly align the ends and starts they should fall in line but you will have to stretch one of the sound files slightly.

Ah ha. This is gold. I'll try this for a work project today. Wicked.

[tigali]

Thanks for all the replies. I suppose I assumed that digital clocks would be precise and matched across different devices. I did a clap at the start of the recording to sync up the files, I never thought I would need one at the end as well
I'll make sure to do that next time.

[jestermgee]

Thanks for all the replies. I suppose I assumed that digital clocks would be precise and matched across different devices. I did a clap at the start of the recording to sync up the files, I never thought I would need one at the end as well
I'll make sure to do that next time.

Yeah digital clocks are just not that accurate in consumer grade equipment, and you would think that in recording gear they would be somewhat but it depends on the amount you spend and their intended purpose. Also, it is very important to make sure all recording resolutions remain the same between devices to reduce the issues.

The difference in clocks could be the case of +5mS in one recorder and -2mS in another. In the real world, no one would notice a recording sounds 2mS slower. But when synching 2 recordings with even a small amount of difference it becomes more of an issue as time goes on.

I have had to assist in dealing with this issue when filming due to the low cost H4/6 recorders used with DSLR style cameras. It's typically fine if scenes are short (5 mins under) but for larger videos of say a concert you can be 5-15 seconds out by the end which is a pain. Trick with these is to ALWAYS record the audio on the camera as a sync source then I just manually make adjustments using cut/drag at points to line things up again.

The software I was thinking of which syncs multiple sources is called "PluralEyes" but it's designed for video applications, not sure if it works for audio only applications since there is no visual reference.

[Tarekith]

Yeah my first thought was that it was a clocking issue, but when he said it happened at only 2 minutes that seemed bit short. Usually these days it takes longer for that kind of drift, like you said 5-15 minutes or more.

[jestermgee]

Yeah my first thought was that it was a clocking issue, but when he said it happened at only 2 minutes that seemed bit short. Usually these days it takes longer for that kind of drift, like you said 5-15 minutes or more.

Yeah, personally if this was going to be an ongoing thing to have to do I would ditch the above solution, sell the Zoom and get either a decent multi I/O interface or a recorder (H6?) that has multiple inputs.

[chrk]

another method is to use a clapper at the start and end of your recordings and use that spike to quickly line up the start and ends. If you can quickly align the ends and starts they should fall in line but you will have to stretch one of the sound files slightly.

Ah ha. This is gold. I'll try this for a work project today. Wicked.

Listen very closely what this does to spill and room sound between the tracks.

[tigali]

Yeah, it was an on the spot solution. We were supposed to be recording a two mic interview that turned into three mics so we had to make do there and then (only two mic inputs on the Zoom) and my friend just happened to have his laptop and portable two channel interface with him, hence the combination solution. In future the plan is to go via a 4 channel interface and record each mic on it's own track into Ableton.
I managed to match them all up manually. They were only 20 min interviews so not that much work but a totally unnecessary pain in the ass, we'll be better prepared next time. Thanks everyone