Export stems of a session

Getting Stuff Done How do I .... ?
#1

Hi.

I have issues when exporting stems. The export seems to run fine, it doesn’t stop in the process, I get to the step where the analysis window is displayed. But the files are “corrupted”.

Here’s my workflow. The project has 2 guitars and a bass. For each, I have a clean and an overdrive track. Also, I record dry, then send each track to a corresponding wet track in which I use Guitarix VST. So that’s 12 tracks (2G+B) x (Clean+OD) x (Dry+Wet).

I set the start/end markers and export master successfully (as mp3). When I export stems of all 12 tracks, some tracks are complete (same length as master export), others are truncated. Besides, when opening the broken tracks in vlc, the total length varies weirdly (I mean the displayed value changes while playing). Also, in the analysis windows, “good” tracks behave as expected, while “bad” ones show wrong times and profiles that don’t match the sound I hear when clicking “play”.

This seems to be reproducible. I did two exports and got the same outputs (diff says files are identical).

Using Debian 12.10 (stable), Ardour 7.3, pipewire 1.4.2 (backport). I can’t easily test on Ardour 8.

Any idea what could cause this? Should I open a bug? What information should I provide? Are there useful tests I could perform? Is it worth filing a bug for a 7.3 issue?

Thanks.

#2

I can’t easily test on Ardour 8.

Have you tried the demo version from this site? It can be installed in parallel to your distro’s version.

#3

It is probably Pipewire. The ALSA backend will likely work.

#4

Thank you guys for answering.

I didn’t realize I could use a binary provided here. I thought I’d have to move to Debian Sid (there is no Ardour 8 backport in Debian 12 Bookworm).

Since Paul thinks the issue is in Pipewire, I’ll investigate this first. I use Pipewire backports so I get frequent updates. Currently using 1.4.2 which is latest.

Should I contact PW to hopefully provide them useful information to help fixing this?

Before I do so, I should try to confirm PW is the culprit. Unfortunately, I’m at a loss figuring out how to use the ALSA backend. I couldn’t find anything in Ardour configuration. Do I need to disable PW system-wise, install and configure PulseAudio, or even Jack? Or is this just an Ardour setting?

Thanks.

#5

Does ALSA show up in this window ?

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In the main menubar, select ‘Window’ and then ‘Audio / MIDI Setup’ to change.

You may have to double click on the master track to set the outputs again once the Audio System is changed, the box right above ‘Comments’

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#6

@Paul, While I had the CPU very busy, I booted up Ardour 8.12 and it gives this error:
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When I quit the process(compiling) that was using the CPU, I can start Ardour, the error never shows and everything works fine.

I do not remember having this issue with 8.6 (UPDATE : it worked because I always killed PipeWire) . Is this worth mentioning in the tracker ? ← I blame Pipewire

UPDATE: I am going to blame Pipewire holding ALSA captive for a while even though apps (Firefox, Audacity) are closed. Ardour, using ALSA, would load and work with a high CPU load after ALL other apps that could be using Audio(through pipewire) were closed for about 30 seconds to a minute or more. Audacity was closed about 5 minutes prior to booting Ardour. Firefox was still open. After closing Firefox, opening ardour failed, then sucessive attempts to open worked fine under heavy CPU load.

#7

Shame on me for not finding that window. Thanks.

That’s interesting. I did the change to ALSA backend as suggested. Indeed I had no sound, I tried to connect master output to soundcard and still no sound, but never mind. I stopped pipewire to be sure.

systemctl --user stop pipewire
Warning: Stopping pipewire.service, but it can still be activated by:
  pipewire.socket

I performed the same exports again and got… the same results. That is master export is correct and a few tracks are correct but others are corrupted. Files are byte-to-byte identical.

Edit: It appears pipewire didn’t stop. I can’t seem to shut it. Tried stop, disable, even sigkill. But I did select ALSA in Audio/MIDI Setup.

#8

Do you get the same results when you uncheck ‘Apply track/bus processing’ ???

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I assume you are exporting STEMS by using the Session → Export → Stem Export in the menubar.

#9

Yes.

Same results with that box unchecked.

#10

Are there any error messages in Ardour after export ? Top Right Green or Red dot. If you click on it, it will show the log. I have had export errors in the past because of missing codecs , particulally if I was using the repo version of Ardour. Have you tried the demo download from the Ardour site ?

https://community.ardour.org/download?platform=linux&architecture=x86_64&type=compiled&paymentSelection=options

The Ardour from the site really does work a lot better overall compared to the distro provided Ardour, which can have seemingly random malfunctions such as what is happening on your system.

#11

Thanks for the hints.

I retried and got no error message in the logs.

I also tried .wav and .ogg exports and got no issue so codec is most likely the problem. I can export as .ogg, so at least I got a workaround.

Not sure where to report the bug. Is the codec included with Ardour? The Debian philosophy is to package stuff separately, so I’d assume a generic mp3 codec is used, but if so I don’t know which package it belongs to. And I wouldn’t have much to put in a bug report since I have no error message.

Thanks for the recommendation about getting Ardour off here. I shall try that.