Add ADPCM Decoder

[geckoxx]

This adds an ADPCM decoder with following limitations:

• only Microsoft ADPCM and IMA ADPCM codecs
• only mono and stereo channels
• only 4bits per sample (IMA ADPCM allows 3bits)

It also expands the Wave Format to support ADPCM and the packetization over a number of samples (PCM) or blocks (ADPCM).
To support multiple data blocks per packet CodecParameters has a new parameter: frames_per_block.

Related Issue: #124
Resolves: #41

[pdeljanov]

Hey, this is really great! Thanks for implementing these decoders!

There are some minor changes that need to be made, and a couple other things that I think need to be double checked, but overall it looks good to me.

A couple general items:

1. Please add yourself to the CONTRIBUTORS file
2. It's not very obvious, but you need to run a nightly version of cargo fmt for the code to be formatted correctly. The CI will complain otherwise.

In terms of testing, have you ran your test files through symphonia-check?

I transcoded a couple files to ADPCM and checked them, but that's a very small test.

Thanks again, and hope to get this merged soon!

[torokati44]

Just FYI, FWIW there's also an ADPCM implementation here: https://github.com/ruffle-rs/ruffle/blob/master/core/src/backend/audio/decoders/adpcm.rs

It might be too simplistic (it has to support only what Flash Player did), but it could still be interesting for cross-referencing.

[geckoxx]

Just FYI, FWIW there's also an ADPCM implementation here: https://github.com/ruffle-rs/ruffle/blob/master/core/src/backend/audio/decoders/adpcm.rs

It might be too simplistic (it has to support only what Flash Player did), but it could still be interesting for cross-referencing.

I will look into it. Seems to be the IMA Codec.

[geckoxx]

I tested my 2868 files (all with the Microsoft ADPCM Codec) and all passed.
I tested also the 16 ADPCM files from this side and all passed.

[pdeljanov]

@geckoxx, thanks for making those changes.

Things look good to me, and your test results are very promising. Once you are ready we can merge the decoder and let it sit in the main branch for a bit.

I'm sure some people will experiment with it, and perform further testing.

[pdeljanov]

Thanks for your work, @geckoxx! Merged!