Add AC-4 format support

[ybai001]

• Add AC-4 MIME type definition
• Add AC-4 format support in Mp4Extractor and TsExtractor
• Add AC-4 Extractor
• Add AC-4 playback support in MPEG-4, MPEG-DASH, TS and HLS

[andrewlewis]

Do you have a sample .ac4 stream that could be used to add an Ac4ExtractorTest just like Ac3ExtractorTest?

This looks good to submit once that's added and the comments are addressed. Thanks!

[ybai001]

Do you have a sample .ac4 stream that could be used to add an Ac4ExtractorTest just like Ac3ExtractorTest?

I talked with content creation team. It should be OK to add a sample .ac4 file. After I get approval from legal team, I'll add it into this contribution.

[ybai001]

Do you have a sample .ac4 stream that could be used to add an Ac4ExtractorTest just like Ac3ExtractorTest?

This looks good to submit once that's added and the comments are addressed. Thanks!

Hi, Andrew,
I have asked content creation team to create sample.ac4 file. And I have one question: How to generate corresponding .dump file in folder library/core/src/test/assets/ts?

[andrewlewis]

@ybai001 You can set the field FakeExtractorOutput.WRITE_DUMP to true temporarily, then copy the file that gets written to the sdcard into the assets directory.

[andrewlewis]

Thanks.

[ybai001]

Sorry for the untidy commit history. I‘m not familiar with the working process on GitHub.
BTW, next week is Chinese new year. I'm afraid that I can't reply in time.

[andrewlewis]

Looks good, thanks! This pull request will automatically be marked as merged when we submit this internally and update the development branch.