Opus encoder

[Palakis]

Features:

• Works for Recording and/or Live Broadcasting
• Track Metadata for Recording (LB metadata is handled differently)
• CBR and VBR modes

Started as an internal PR on my fork. Original conversation here: https://github.com/Palakis/mixxx/pull/3

[Palakis]

Among other small bugs, here's an interesting comment by @daschuer from the original pull request:

The encoding type options are getting overwhelmed. Could you add a tooltip for each option, with a > hint for what it should be used:

"Mp3, old but plays everywhere"
"Ogg Vobis, the free an better codec"
"Opus, the Vobis successor"
"AAC ...

We can optimize these strings now or later

[daschuer]

Thank you for this PR. Is it a candidate for 2.1?
Is it ready for reviewing?

[Palakis]

@daschuer It is a candidate for 2.1, ready for reviewing.

[JosepMaJAZ]

We currently build against opusfile 0.7 and opus 1.1.2, which does not contain some of the functions required. We need to update (windows) buildserver libs.

[Palakis]

Hmm, SampleBuffer causes no trouble on my machine, but seems like Travis can't find it...

[Sa-Ja-Di]

So there is a chance that in the next version streaming in Opus is a possibility? I would love that very much as even 48 kbps in Opus is a damn fine quality. Hope you can make it :)

[daschuer]

Travis build the merge with master. I can reproduce the build failure on my stem after merging master. So I assume it is a kind of merge conflict.

[daschuer]

@Palakis: will you have time to finish this for Mixxx 2.2?

[Palakis]

@daschuer Sure! I'll have a look at the build failure next week and see what's left to fix.

[Palakis]

I fixed the merge conflict by rebasing this branch on the latest master. Linux CI passes without issues, however Windows and macOS fail with "undefined symbol" errors, each platform showing a different set of missing symbols.

Windows:

   Creating library win64_build\mixxx.lib and object win64_build\mixxx.exp
opusfile.lib(enc_API.obj) : error LNK2019: unresolved external symbol silk_encode_do_VAD_FLP referenced in function silk_Encode
opusfile.lib(enc_API.obj) : error LNK2019: unresolved external symbol silk_encode_frame_FLP referenced in function silk_Encode
win64_build\mixxx.exe : fatal error LNK1120: 2 unresolved externals

macOS:

Undefined symbols for architecture x86_64:
  "_opus_encode_float", referenced from:
      EncoderOpus::processFIFO() in encoderopus.o

[uklotzde]

I added some comments for some minor issues that should be fixed before merging.

There are even more minor code style issue (formatting, missing curly braces, const naming convention, C-style casts, ...) that you may leave as is if no one else complains ;)

[Palakis]

@uklotzde Thanks for your review! Fixed these issues.

[uklotzde]

Thanks @Palakis for getting this in shape quickly. This is a nice feature for 2.3, although I'm not able to test it myself. LGTM.

[uklotzde]

Merge?

[daschuer]

Yes.
I think we should wait for Jenkins had all 2.3 build with this included and than announce this feature at the forums and mailing list asking for testers.

[esbrandt]

The OPUS error message is hidden behind other error message (moved downwards in the screens for readability).

• When broadcasting:
  The warning is displayed beneath the connection error message.
  

• When recording:
  The warning is displayed beneath the recording error message, given no path is set in the recordings folder (default)