Asymmetry in "sync" phase adjustment

[mixxxbot]

Reported by: jgehrcke
Date: 2014-06-07T23:42:53Z
Status: Fix Released
Importance: Medium
Launchpad Issue: lp1327640

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Using 1.12 master from May 2014.

I have had a situation where syncing from left to right yielded the correct phase adjustment, whereas syncing from right to left produced a minor phase offset.

I could do that reproducibly, i.e. when I pressed the left sync button the two tracks were synced perfectly, but when I then pressed the right sync button, the two tracks were slightly phase-shifted. When I then pressed the left sync button again, they were perfectly aligned again, and so on... back and forth.

I have had this before but did not investigate properly. This time, I tried to reproduce it with the same two tracks over and over again, and could reproduce. However, after Mixxx restart I could not reproduce using the same two tracks. Looks like some of my actions in the course of a Mixxx session brought Mixxx into this "malicious" state. I have no idea what that could have been unfortunately.

This asymmetry contradicts my understanding of how the underlying implementation should work -- in my naive view, this operation should be entirely symmetric, i.e. we have two markers and phase adjustment should align them. The difference between left -> right and right -> left should only be which of both tracks makes the "jump", but the alignment should eventually be marker-on-marker in both cases, right?

Some might ask: if left->right works, but right->left does not, why don't you just use left->right? When we have a silenced track and one that is currently playing on master, then obviously, we do not want the master one to make the jump, so the sync direction is predefined.

The music I was doing this with is electronic music, about 120 bpm. The beatgrid was set perfectly.

[mixxxbot]

Commented by: ywwg
Date: 2014-06-08T02:11:28Z

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Are you using master sync? Is quantize on? What about keylock?

[mixxxbot]

Commented by: jgehrcke
Date: 2014-06-08T12:21:55Z

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I am not exactly sure regarding "master sync" but I understand that this is a new feature only available in special themes. I am using Deere and I have used the "sync" button. Hence, I guess I did not use master sync.

I have observed this with quantize and keylock both activated.

[mixxxbot]

Commented by: ywwg
Date: 2014-06-08T15:50:01Z

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It could be that when you sync with the right deck, it's using an out-of-date position to sync against. The right deck seeks, and the left deck is already one buffer ahead.

You should do testing with the Latenight-Stacked skin, which has all the new features. Master sync is engaged by clicking and holding the sync button. But anyway, one-shot sync should work so I'll take a look at this.

[mixxxbot]

Commented by: jgehrcke
Date: 2014-06-12T10:22:59Z

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FWIW, I have observed this behavior also with Latenight-Stacked, without using master sync. Again, I somehow got there, and a program restart made the problem disappear (for a while).

[mixxxbot]

Commented by: jgehrcke
Date: 2014-07-02T17:46:30Z

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Sorry to bother you with that, but currently this for me is the most annoying issue when using Mixxx 1.12 in production. I still cannot reliably reproduce, but this happens over and over and really bring you into trouble when you are trying to precisely mix. Is someone investigating?

[mixxxbot]

Commented by: ywwg
Date: 2014-07-09T12:08:35Z

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I'll take a look

[mixxxbot]

Commented by: ywwg
Date: 2014-08-13T16:25:26Z

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#307

[mixxxbot]

Commented by: ywwg
Date: 2014-11-14T14:10:49Z

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This was fixed

[mixxxbot]

Issue closed with status Fix Released.