Emulator

If it isn't too much to ask, mind giving us a recording?

Proof of concept is a good thing around these parts.

GPLv2+ is compatible with Dolphin, so we could integrate that.

I'm not completely clear on what you're comparing though. Basically, you're taking the audio dump from Dolphin and using several ways to do DPL2 decoding on that same dump?

Actually I am comparing most of them directly.

The decoding using ffdshow's method (this is the one integrated in dolphin) is doing something wrong to the audio signal and making it sound the way it wasn't meant to sound.
I also integrated the decoding code from PCSX2 to Dolphin to compare real time decoding as I had read that it was better than FFDShow's, but it turned out to be worse.
I tested my AVR decoding (Dolby approved) connecting my computer's HDMI cable to it.

The decoding from foobar2000's DSP plugin was tested taking an audio dump. I also ran this dump on GraphStudioNext to force the use of ffdshow's decoding to be sure that it is not a bug introduced on the code used by Dolphin.
In Zelda: TP the surround effect is very good, I will take an audio dump from it and post it here later today. Sadly I do not know how to record 5.1 audio so one would need to install foobar2000 and the DSP plugin to test "Free Surround" algorithm, and ffdshow codec to test ffdshow's algorithm.

The link that I posted from hydrogenaudio has a Dolby ProLogic II encoded sample (channelcheck.mp3), it is perfect for simple comparisons between all decoding methods.

If you feel like working on integrating that code I have no objection. I'm not sure if many active developers are interested in the feature enough to work on it themselves, but if you care and have the knowledge to do it, sending a patch will likely make it happen.

Does a GameCube Service Disc have a test suite, or anything else for any of the sort, for ProLogic II? I feel he may be onto something here.

Just checked, it can only test Left, Center, Right and Disc Streaming.
When emulating on Dolphin (tested with r8062, Direct3D11 and LLE with WiiU's DSP ROM) there are lots of error messages, and for some reason the sound test doesn't work correctly on the OpenAL backend (tested with X-Fi Titanium and OpenAL Soft), only on XAudio2. It seems that the buffers are not played fast enough.

I looked through "Free Surround" source code to try to implement the algorithm on Dolphin, and it is definitely too much for my current skills. Maybe in 1-2 years I might be able to do something unless someone does it before.

I sure hope somebody picks this up. Why have a surround sound feature when it's broken?

@delroth @JMC4789

Would be great if this is corrected for 5.0

Anyone working on this already?

I managed to capture a sample with proper A/V sync using nVidia's utility, if anyone is interested the file can be downloaded here:
https://mega.nz/#!o0dHjRBI!_w-By4njDo4wgiYoKmuslghxZtGqTwPZdCA3LaOxODQ

The first audio track is DPL2 encoded, and the second audio track is the first track decoded into 5.1 channels using foobar2000. With this sample it is far easier to see how better FreeSurround algorithm is compared to FFDShow.

The FreeSurround from Kodi does not depend on boost and seems to be easier for me to understand, so I will try to implement it on Dolphin if no one else is doing so already.

Kodi's FreeSurround plugin source code:
https://github.com/kodi-adsp/adsp.freesurround

I'm currently working on this issue, but I'm not sure when I could finish because of my own job.
Yes, Kodi plugin source code is more understandable, however there is a small problem that audio buffer of Kodi is not multiplexed, so the code cannot be used to Dolphin directly.
I'll post again when I have another progression.

OK, thanks.
For those interested, I made another video but now from Super Mario Sunshine. On this sample FreeSurround literally destroys the FFDShow decoder, and I even feel it is a little better than my Dolby-approved reference software-decoder (PowerDVD7).

FFDShow even sends the sounds of the ocean waves to the back speakers, while both FreeSurround and the reference send only the drums to them.

https://mega.nz/#!91U2lQgQ!u9qDoeanP1OORYqHCpvNgeVNtlKn7CKPrdW_IURIrms