Extracting audio from Rear Pheles ~Red of Another~ (PSVita) by mkdude at 7:47 PM EDT on October 29, 2016
I've been working on extracting and playing back the audio files from an obscure PSVita visual novel in Japan. I was able to dump the game contents and extract the files from the Unity asset files (resources.assets and resources.assets.resS).
When getting the files, they appeared as .vag, but playing them back in foobar2000 caused problems with glitchy and slowed down audio. I looked into it and applied GENH headers using the following settings:
Input file format: Playstation 4-bit ADPCM Header Skip: 0 Interleave: 0x10 Channels: 2 Frequency: 44100 No loops
While the audio is better, it still has problems with cracking and garbled sounds, but at least the music is somewhat listenable. I've tried adjusting the Interleave, but that only made it worse. At this point, I'm not sure how to further improve the audio quality. I've read that the Vita supports HE-VAG which is what this game might use, but I'm not 100% on that. Any help on this would be greatly appreciated.
I tried different options for header skip including setting it to 0x30. It doesn't seem to make a difference in the audio. Something tells me these files are encoded in HE-VAG format.
Yeah, having looked at the files now, I can say that the ADPCM block flags looks non-standard for one thing. I have no idea how HE-VAG differs, and I've never dealt with it before, so I probably won't be able to help.
Having done some digging around, it seems that someone has managed to find a way to decode HE-VAG files. The only limitations are that the audio has to be in Mono and will always output at a frequency of 44100 regardless of input.
When testing this program using ChillyBilly's rip of Corpse Party, the files played fine but sped up (since the original files are at a frequency of 22500). This doesn't help with Rear Phele's audio since the original is in Stereo. Still, it's good to know that at least it was being looked at in one point.