I encountered this bug back on version 2.0.3 on OS X 10.8, and it wasn’t in the bug tracker, and still isn’t in the bug tracker as of 2.0.5, the current version I’m on. I’m running OS X 10.10 now, and I don’t recall if I used the .DMG or the .ZIP, whichever one came without the help files is all I remember.
I’m also running Windows 7 via BootCamp and I only have this issue on OS X, which indicates it’s not my hardware that’s the issue, and Gale Andrews responded to my email back in 2013 saying other OS X users had reported it, which also points to my hardware not being the issue. Also I’ve had multiple hardware swapouts/upgrades and the issue persists.
This bug is hard to reproduce on-demand. There are a few unknowns regarding when it occurs, so I’ll mark those in bold but from what I do know, it happens when I open (or drag-in) at least one uncompressed audio file such as WAV or AIF(F). After some amount of time/edits while working on it, regardless of what is or isn’t running in the background, the first approximately 7 seconds of audio get apparently random artifacts. I haven’t counted down to-the-sample to see what length of time exactly is getting corrupted, but it’s always the same length of time.
I don’t have any samples currently but within the next few days I’ll link to some, as well as the uncorrupted version of the same audio, as well as a null test to show exactly what the data is. Visually, every few samples are set to random values, resulting in lots of pops and clicks. Sometimes it’s worse than others, and I don’t know what causes that; sometimes the offset on each affected sample is enough that I can just zoom in and manually correct it. There have been times when I’ve exported audio and only 3 or 4 samples were affected.
Some times, however, it might as well be white noise, so many of the samples are all over the place and it’s far too many to fix by hand (7 seconds @44100 samples/second comes out to… a lot).
I don’t know what causes this variation. At one point I made four tracks, and the last three tracks all had this issue, and the style of the corruption was almost identical, and then a few days later I went to export a track and it was much worse.
Oddly enough, this only happens if there’s actually data there. If I simply insert 7 seconds of silence at the beginning of every clip in audacity, this issue does not arise, because there is apparently no data to corrupt or something. Unfortunately, adding 7 seconds of silence to every clip is not really a feasible workaround.
The issue becomes apparent when I select audio and Export it, or when I select two tracks and Mix them. Sometimes the issue arises when I hit the play button, and when it does, it’s often times only in one channel rather than both channels. Stopping the playback and starting again almost always temporarily fixes the playback, but at that point the audio is corrupted, so if I try to save or export anything, it comes out corrupted, and I have to add some silence at the beginning of the track and then open it in Windows to trim the silence out.
Gale suggested that “slightly corrupted .WAV files” might be behind the issue, but I have a feeling something is getting seriously fucked with the .AU files in the temporary folder, because this happens no matter how I import audio, and it happens every time I import uncompressed audio, it’s just a matter of how long until it happens every time.
Restarting Audacity makes the issue go away, at least, until it decides to start happening again, but if I’m in the middle of a project and it starts happening, I have to Undo back to before it started, add 7 seconds of audio to the beginning of EVERY clip, mix it all down to make sure it’s still OK, Undo back to before I mixed it down but it still had all the silence, then Save it. Otherwise the corruption gets saved in and when I restart Audacity and re-open the project it is locked in there permanently.
This happens regardless of where I get the .WAV/.AIF(F) files from. I can get them online, I can create them in Audacity on a friend’s native Windows machine, I can create them in my BootCamp Windows, I can even make them in OS X in any software. As long as it’s a lossless file, this always happens.
Gale suggested I adjust my dithering options so they were turned on, but they already were, and every other attempt at a solution that was suggested to me was either already set up that way, or yielded no results. I’m on version 2.0.5, the bug is still present, and yet it obviously hasn’t been deemed important, frustrating, or catastrophic enough to bother listing it, so I can’t check the listings and see if they’ve even fixed it. Since it can’t be immediately reproduced and takes an apparently-random amount of time of fiddling around before it starts to occur, I can’t just download the latest version every time it comes out and see if it’s been patched, so that’s completely useless. (For what it’s worth, each time I’ve done that, it’s not been patched. Eh.)
The issue occurs regardless of how much free space I have on my storage disk, and I haven’t checked my memory to see how much of it is in use. I am aware of a particular Linux bug that causes Audacity’s CPU usage to climb constantly until it reaches 100%, so there might be something like that going on in OS X, I’ll have a look as soon as I get some sound to corrupt.
It also happens when I have a mix of compressed and non-compressed files. I can be working with MP3s and drag in a WAV file and it will start happening eventually, whereas no amount of fiddling with MP3s ever causes the issue.
I think I’ve listed everything. I even went over the old bug report (sent via email, since the forums were being silly and wouldn’t let me activate my account). If I’ve left anything critical out, please let me know. I’m now going to hop back over to OS X and start editing some AIFFs and see if I can reproduce the issue before I get too tired.