support vinyl auto-detect

[Owen Williams]

It should be possible to automatically detect what type of vinyl someone is playing. In the preferences, there could be a "detect" button. When pushed, mixxx:

* listens to the input for a signal
* loops through all of the vinyl types, creating a timecoder object and then attempting to read timecodes
* when valid timecode is read (95% successful samples read in a range of 100), that's the right one
* also detect speed -- if it's about 1.35 times as fast as we expect, it's 45rpm

maybe we could also keep a timecoder around initialized for the reverse side in case someone decides to flip the record over, which I've seen happen.

[Mika Haulo (mhaulo)]

Would it be possible to skip the detect button so that detecting vinyl type wouldn't require any user interaction? Once detected, the vinyl type could be saved to configuration as the default vinyl type. If the vinyl type changed (not very likely) and the decoding failed, detection would be run automatically.

[Ambrosio Barceló (bronxio)]

Other software work like this:

- Serato works with CV02 and CV2.5 (the same timecode signal that CV02, but +6dB) only. It detects the side automatically.
- Traktor 1 works with its own MKI timecode only and Traktor 2 with its own MK2 timecode only. Autodetect the side as well.
- VirtualDJ has its own timecode vinyls and CDs, but it's compatible with other brands. Otherwise, they say that user must select first the timecode type first in the dropdown menu (even de Serato and Traktor sides, the same procedure than Mixxx):

VirtualDJ info: http://www.virtualdj.com/manuals/virtualdj8/settings/audiosetup/timecode.html
dropdown menu screenshot: https://es.virtualdj.com/image/71486/207049/timecode.jpg

So, the side may be autodetected, but I don't know how they do.

I think there are 1, 2 and 3 KHz timecode base tones depending on the brand. Here you can hear the Serato CV02 (B side), Traktor MK2 (not compatible with Xwax/Mixxx, B side) and MixVibes:

https://www.youtube.com/watch?v=uaPRSR_Iqgg

[Ambrosio Barceló (bronxio)]

Just for other team experiences watching:

I downloaded the last VirtualDJ version (v8.2.b3870 PC) and they added the "Autodetect" option in the control vinyl dropdown menu. But it works once only for everyone (at least with Serato CV02, Traktor MK2 and MixVibes). But if you set that it's side A of the Serato CV02 and change to the B, in some second decimals it do a little jump in the song track when it starts to play it (I guess because timecode position correction after detection is complete, but it does even in relative mode) and automatically change the side. It's the same with Traktor MK2 (added recently, but it doesn't work that good than Serato and MixVibes, I can see how it miss the timecode position with fast backspins).

Maybe ywwg is right, but I don't know why the VirtualDJ team don't keep the autodetect option after the first detection.

[Ambrosio Barceló (bronxio)]

Forgot to add the VirtualDJ screenshot.

[Be (be.ing)]

There has been no progress on this lately, so I am removing the 2.1.0 milestone.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/5788