Extract metadata for youtube, soundcloud & mediaccc

[B0pol]

• I carefully read the contribution guidelines and agree to them.
• I have tested the API against NewPipe.
• I agree to create a pull request for NewPipe as soon as possible to make it compatible with the changed API.

Extraction for metadata which were added not so long ago (now), but only for PeerTube

fixes #393

[wb9688]

According to https://github.com/voc/voctoweb/blob/master/app/admin/event.rb#L115, media.ccc.de does actually use ISO 639-2. Since they have e.g. deu, it means they're using ISO 639-2/T.

[Stypox]

Why is the license function called "getLicence" and not "getLicense"? I think it should be renamed

[B0pol]

Why is the license function called "getLicence" and not "getLicense"? I think it should be renamed

Because I'm learning UK english, not American version. In contribution guidelines, it's not stated to use american english.

[wb9688]

@Stypox: I generally prefer US English as well for programming, as that's basically the default. I learnt UK English at school though.

[Stypox]

Oh, didn't know licence was a word, I only ever came across license. Then don't consider my complaint ;-)

[Stypox]

While you are at this, could you move all of the metadata methods in the base StreamExtractor.java above the "Helper" section? It is confusing to find a helper function sorrounded by interface functions

[wb9688]

@B0pol: Could you rebase and fix the issue for YouTube and SoundCloud? Don't bother making it an enum for now.

[B0pol]

@wb9688 done

[wb9688]

Could you clean up the commits?

[Stypox]

@B0pol could you rebase this one last time? Then it should be absolutely merged 🙈

[TobiGr]

Yes, that just needs to be rebased. I reviewed the code before, but forgot to approve it

[Stypox]

I rebased; the related tests run well on my end; I think this can be merged. @TobiGr

I also included a fix for SoundCloudStreamExtractorTest, which contained two test-initializing functions which were nor static neither marked as @BeforeClass, but instead were marked as @Test. This caused them to be run at a random time, so sometimes the extractor would be initialized beforehand, other times not, causing NullPointerExceptions. Furthermore, such @Tests were expected to throw GeographicRestrictionException and SoundCloudGoPlusContentException inside fetchPage(), so I added a try-catch that ignores those exceptions. You may ask how the tests can pass if fetchPage() fails: they pass since the exceptions are thrown after everything has been extracted (see these lines). I don't know why an exception is thrown if everything can be extracted without issues (@TiA4f8R could you investigate?), but this is unrelated to the scope of this PR.

[AudricV]

I don't know why an exception is thrown if everything can be extracted without issues (@TiA4f8R could you investigate?), but this is unrelated to the scope of this PR.

For what tests/streams/tracks? I don't understand.

[Stypox]

@TiA4f8R take a look at the changes in SoundCloudStreamExtractorTest

[AudricV]

It throws an exception because no streams are available for these tracks.

[Stypox]

Then the test for video streams should fail, but it doesn't (unless it is suppressed, I didn't make sure that was the case)