ErosQ - Stereo channels swapping around

[Oktan]

I have an audio file (in OGG) composed of a voice saying "left channel" and "right channel" on the respective audio channels for checking the polarity of some unmarked headphones. I have now noticed that the polarity seems to randomly change. Sometimes it's wrong (or maybe right?) when I start up the player, sometimes it's the other way around, and sometimes after I've played a few other tracks and I go back to the stereo test, it has swapped around.

[dconrad]

Can you link your test file? That sounds bizarre. Curious if I can reproduce it here.

[Oktan]

Can you link your test file? That sounds bizarre. Curious if I can reproduce it here.

Yes, of course. Here you go: https://files.catbox.moe/011b3k.ogg

[dconrad]

I am able to reproduce it - not by rebooting the player or by repeatedly stopping and playing the test file, but only by switching back and forth between the test file and some other file. It does seem to be about a 50% shot which way around the channels are.

My gut say it has something to do with the way we're feeding the data to the DAC on this particular device, but I would also like to try some different file types (both of the test file and the "alternate file") and see if there is any influence there.

Edit: I converted the test file to flac and the issue still occurs, so it's not a file type issue.

[dconrad]

Also tried it on m3k, and couldn't seem to reproduce it there. So whatever it is, it's unique to the eros q.

[Oktan]

Also tried it on m3k, and couldn't seem to reproduce it there. So whatever it is, it's unique to the eros q.

I should also state that I'm using the native port, and that I have an Eros Q that is actually an Eros, and it has a microUSB port.

[dconrad]

Good to know that it's not dependent on the particular hardware revision, because I'm using the newer revision with USB C.

I think I might have stumbled across it being related to the sample frequency - I've got a couple tests if you wouldn't mind seeing if you can still reproduce the issue in a couple circumstances.

Maybe find a pair of files where you can go back and forth and sometimes the channels swap sides, and a pair of files where it doesn't seem to ever occur? (if I'm on to something, I believe you should be able to find a set of such files).

  - What are the frequencies of all 4 relevant files (^^) under Track Info?
  - Under Playback Settings, what do you have Frequency set to?
  - Try repeatedly changing the frequency setting while playing back the test file. Any effect?
  - Try setting the frequency setting to something other than Automatic (anything 96khz and under - I was able to reproduce this with this setting set to 176.4khz and 192khz, but have been unsuccessful with the lower values). Can you still reproduce the issue?

[dconrad]

So depending on how much you value higher sample rates, I did make a build which only supports 44.1k. If you want to give it a spin and see if you can get the issue to occur at all, feel free: https://www.dropbox.com/s/w640z6o1sfcg17x/rockbox-erosqnative-44.1k-c0a99b88e4d-03-18-2023.zip?dl=0

[dconrad]

Another day, another build - after floundering around a while, I managed to, I think, find the culprit. Give this build a try and see if you can get the issue to occur, because I can't seem to, so this may fix it: https://www.dropbox.com/s/vkerk3zqm100zv4/rockbox-erosqnative-swapfix-e97155c44-03-19-2023.zip?dl=0

It corresponds to this patchset: https://gerrit.rockbox.org/r/c/rockbox/+/5166

[KarlLeach]

I will try it