Audacity Forum

Update:

I haven't had this problem for a couple of weeks now. The only change I'm aware of is the temperature - it was pretty hot during the time I was doing the testing. Now recalling the occasion when the phase jumping consistently started 30 seconds or so into recording, this is starting to look like a thermal problem. As for the difference between Audacity 1.2.6 and 1.3.12, maybe 1.3.12 just makes the CPU do more work and so heats it up more.

- DickN

That sounds plausible. Perhaps you could try running a CPU temperature monitor - there are several free ones on the web and some motherboard manufacturers include one in their motherboard software pack.

My "thermal problem" hypothesis isn't quite dead yet, but it has a bad cough. Room temp now is 62-64 F to save fuel, and I'm finding that when I start receiving audio in Audacity, there's a 20 - 50 % chance of the process waking up in the frequent phase jumps state. This applies to Monitoring, Record and Record Pause. My workaround is to always start off in Record Pause and listen for a while to check the operation before starting Record. If the signal starts off clean, there's at most a 5% chance of getting a phase jump even if I record a whole side of a cassette (45 min) (This is different from the system's behavior at higher ambient temperatures.). If it starts off jumpy I hit stop, delete the empty track and try again. Sometimes I have to do this several times before getting a clean start. That's after setting the affinity to CPU0 only. Again, when the audio from Audacity is jumpy, if I set Realtek to pass direct sound to the headphones that signal is clean.

Is there any difference in the timing of the steps when Audacity initializes the input source between versions 1.2.6 and 1.3.12? It does appear to be a randomness in the initialization. Might there be a window of opportunity for Vista to switch tasks where no window existed in 1.2.6?

My instinct is leaning towards this being a sound card driver problem.

This is an on-board audio (sound card built into the mother board)?
Have you checked on the mother board manufacturers web site to see if update drivers are available?

<Device Manager->Sound, video and game controllers->Realtek High Definition Audio->Update Driver> says driver is already up to date, the best driver is already installed. I have version 6.0.1.5910 dated 8/4/2009.

Funny thing, last year I found a newer driver when I was experimenting with this problem. I remember installing the newer one and finding some new features (I don't remember all of them. One was a peak limiter for the headphone output), but the Stereo Mix bus had disappeared. There was also a difference in the Volume Mixer, I think one of the inputs had a different name. I have a MIDI app which doesn't show up among the inputs, so the only way to record from it is via Stereo Mix. I believe I tested it and found it didn't fix the phase jumps. I did a System Restore to revert to the driver I'm using.

Could be the one mentioned above is not 100% compatible with my motherboard and therefore is not qualified when Windows searches for an update.

Windows only looks at the drivers that are on your computer and any generic drivers that it has. It does not check the manufacturers web site- you should do that manually.