[amo] Audio glitches-Tempo change in Session View

[gavinwhiteley]

http://forum.ableton.com/viewtopic.php?f=26&t=109072

I may have spoken too soon.
The key part of the aforementioned issue is mostly resolved - when tempo changes in Session View, the Clip playback location and Track Status Display remain in the same place, and don't change position in the clip.

However, the audio bufferins appears to work differently in 8b25 than 7.0.14.
By "differently", I mean that I can open a large multitrack session in 7.0.14, RME sound card buffer at 256 samples, and freely change Scene tempos without an audible glitch.

The same session, opened in 8b25, sound card buffer of up to 1024 samples, the same activity can give me audio glitches when I switch tempo using scenes. With b25 and 256 sample buffer, I get an audio glitch on every single scene tempo change, across the audio outputs.

I recognize that 256 samples is a pretty low sound card buffer, but this demonstrates that Live 8 is handling the situation differently that 7.0.14

More graphically, and perhaps more importantly: playing a scene in the above large session, and scrolling the top Tempo field up/down with the mouse, I can get the entire graphic display to freeze for up to 10 seconds. Audio still plays, but each Clip Slot / Track Status Display / Track Volume is stuck when this happens - mouse cursor still moves, though.

The session I uploaded for the original forum topic does not cause this, as it is only one track. I will try to put together a larger uploadable session to demonstrate this issue. In the meantime, let me know if I can answer questions to better describe or narrow down this behavior.

[gavinwhiteley]

I am uploading a 111MB Live Pack that can demonstrate what I described above. You can download it from:
http://drop.io/majorscaleaudio

It should be fully uploaded 30 minutes from... now.

It takes a lot of tracks to amplify the problem enough to be clearly audible.
All my projects require lots of tracks, so this is very relevant to my use of Live 7... and hopefully, 8.

Same operation as the last Live set I uploaded for this issue: use keyboard keys to trigger scene tempos without stopping the playing clips. With the sound card buffer at low settings, it can be seamless in Live 7. Same file/drive/sound card settings with 8b25 gives audible audio glitches upon tempo change.

Please let me know if there are any questions regarding this issue or the uploaded file.

I will try the same with 8b26, but I don't expect different results based on the release notes.

Thank you!

[gavinwhiteley]

Uploaded THX_vb26Demo.alp in which it may be easier to hear the audio glitches. Both packs at:
http://drop.io/majorscaleaudio

Live 7 I can barely get audio glitches ([5206] was attributed to "disk overloads") at my sound card buffer of 128 samples, on each tempo change, whether triggering a scene tempo change or scrolling in the Tempo field

Live 8b26 I easily get glitches at sound card buffers of 128/256/512. Lower the buffer, more prevalent the glitches... of course.

Audio clips only, no warping, no Fade, no effects, no plug-ins, no Simpler/Sampler. All preferences identical between Live 7/8.

If I can be more helpful in describing the problem, please let me know.

[Amaury]

Hi,

I renamed the thread now as our attention is well directed to the older problem, which indeed was fixed. Thanks fo rthe detailed description and files, I am now downloading the files.

Regards,
Amaury

[Amaury]

Hello,

Do you still get the same problems with the latest beta?

Regards,
Amaury

[gavinwhiteley]

Unfortunately, yes.
b28, and the release 8.0.1.

I still experience the audio glitch (click/pop) when triggering a scene with a different tempo, with reasonable sound card buffers and large sessions (1.1 GB RAM usage, 50 tracks, even if only a few tracks have clips at any given time)

I get this with audio clips, or Sampler files triggered by MIDI clips.

With my Global Quantize set, the glitch happens not at the moment I trigger the scene, but the moment at which the scene is fired and the tempo shifts.

If I set my sound card audio buffer to 2048 samples, it appears I can avoid all these occurrences.
That, or using the same session in Live 7 with a 256 sample buffer.

If I were to diagnose it from the outside, at risk of appearing completely ignorant, I would speculate that the Live 8 audio engine is buffering less audio data than Live 7 (perhaps to enable Complex Pro?), or that some behavior has been added to "Warp Off" mode that does not allow the audio clip / Sampler file to completely ignore Tempo changes.

[gavinwhiteley]

I should add: The bigger the scene tempo change, the more likely / severe the audio glitch is.

e.g. Playing a "240 BPM" scene, then triggering a "230 BPM" scene - does not result in an audio glitch if my sound card hardware buffer is high enough (1024 samples) in Live 8.

Playing a "240 BPM" scene, then triggering a "490 BPM" scene - this gives me the audio glitch at 1024 samples in Live 8 (so far not at 2048 samples in Live 8, or 256 samples in Live 7). Like the sound of the audio clip(s) play position shifting a few samples, enough to create an audio transient where there shouldn't be one, but not enough to create the perception that the playback time has changed.

[Amaury]

Hi,

Would it be possible for you to send me an example? I'm trying but can't reproduce this.

Regards,
Amaury

[gavinwhiteley]

I found out how to avoid the problem, but not the cause of it.

To sum up: I have one very large (20GB) session, with audio tracks and Sampler instances in both Arrangement and Session view (but I'm playing in Session only). All audio tracks appear in Arrangement, most are also in Session.

In Live 8, it takes up 1.5GB of RAM on my WinXP machine, and I get constant clicks when I switch tempo at a reasonable sound card buffer setting of 512 samples. "D" never lights up, and I have a super-fast SSD anyway.

I can get around the clicks with a sound card buffer of 20488, but this is a band-aid.

If I delete all audio clips from Arrangement View, my RAM usage drops from 1.5GB to 1.25GB, and suddenly the glitches disappear when I do the same things.

1.5GB RAM doesn't seem like too much to ask, even on a WinXP machine. And the session didn't do this in Live 7.

Questions:

- Is Live 8 using more memory than Live 7 for the same project? I've read other threads hinting at this.
- Is there an absolute ceiling around 1.2GB RAM at which Live 8 on WinXP becomes unstable/strained? I thought up to 2GB would be no problem (on a 4GB RAM system, 3.25GB RAM reported in System Properties... the usual).
- Is the presence of audio tracks in both Arrangement and Session View somehow straining the system so much that the audio glitches occur when triggering new scenes/tempos? Deleting 90% of my Session clips does not stop this glitches - deleting 90% of my Arrangement clips does, however.

Unfortunately, I cannot send my actual session with audio files - even if size was not an issue, I am working with the original archived tracks of, shall we say, a very well-known band.

Thanks for your help!

[gavinwhiteley]

OK, it's less of a memory managment issue, than an Arrangement + Session issue.

I deleted all VST plug-ins and most Sampler tracks, got the projeect down to 900MB of RAM usage. Still had the audio glitches, predictably whenever I changed tempo in Session View.

After deleting *almost* (80-90%) of the clips from Arrangement View, the glitches disappeared.

Surely a project in 900MB of RAM should not suffer any memory management issues in WinXP when Live is the only application running on a 4GB RAM machine, regardless of paging file settings, /3GB switch, etc.

So I have no choice but to think it's the presence of a large number of Arrangement View clips that is weighing down performance in Session View - even when no Arrangement View clips are actually playing (all tracks in Session View are full of clips, so no Arrangement View clips are playing).

[Amaury]

Hi,

Thanks for keeping investigating. Question: are any of the Arranger track playing at the same time as some Session view tracks, or are they all "punched out"?

Regards,
Amaury

[gavinwhiteley]

They are all "punched out". Only Session tracks are playing.

Thanks!

[gavinwhiteley]

FINALLY GOT IT.
To sum up: Big session, 96+ tracks, lots of unwarped clips in Arrangement, which I ctrl-drag (copy) to Session for playing in shows.

But playing in Session View, changing tempo (Scene tempo, or scrolling in Tempo field) gives me minor audio glitches... only in Live 8, not in Live 7.

The cure? Either...
a) Delete all clips from Arrangement View, or...
b) Warp all the clips in Arrangement View.

I would describe the bug as:
"When changing tempo in Session View, presence of unwarped clips in Arrangement View (even if not playing or "punched out") may cause audio disruptions/glitches."

It's taken me many months and threads to get to the bottom of this one. I'm going for a drink now...

[Amaury]

Hi,

Thanks a lot for all the details. That said, it's hard for me to reproduce the issue from scratch. So, I'd like to ask: if you reduce the size of the set, can you still make it happen? The goal would be to get the set to a manageable size, so that you can send it to me. Do you have time to give it a try?

Also, do the glitches happen when you open the set and start playing the clips in Session view only, or, does it only happen if you start by playing the Arranger, and then launch clips in Session, punching out the Arranger?

Regards,
Amaury

[gavinwhiteley]

Hi Amaury,

Not to brag, but the session in question uses original archived multitracks of the most famous rock band in history, and it is not possible for it to leave our very secure location.

I can send you an .als with no audio files if you wish.

The glitches happen when I:
1) open the set and start playing the clips in Session View only, and

2) start playing from Arrangement View (after pressing "Back To Arrangement" of course), then switch to a scene in Session View (thus changing the tempo, as all my scenes do) and "Punch Out" the Arranger.
Of course no large multitrack session can go without sound card buffering. In Live 7, I could run my session with a buffer setting of 512 samples on the RME HDSP MADI card (running at 96k), glitch free.

Same session on Live 8, I had to run it at 2048 samples to be glitch free - until I warped all the audio files in Arrangement View. Even though these files are all punched out and I am actually playing un-warped clips in Session View.

All clips in Session View are copied from Arrangement View, so there is one set of audio data referred to by a clip in both Arrangement View, and Session View. With the Arrangement View clip warped, playing the unwarped clip in Session View with changing tempo is now glitch-free at 512 sample buffer... just like Live 7.

And not 100% of the samples have to be warped in Arrangment View - but in my session, it had to be at least 90% of them to eliminate the audio glitch from popping up at this low buffer setting. I tried but could not find a parameter for how many unwarped clips could still be left in Arrangement View - which tracks they were on, how long they are, etc.

Oh, I should clarify that all my audio files are one file format at 24-bit 48k WAV. Sometime I am playing these files from Sampler on a MIDI track in Session View, but the glitch / lack of glitch was the same as if I was playing the audio files as audio clips in Session View.

I hope this is helpful and thorough without being monotonous.