RPi 2 with a USB soundcard, a Terratec Aureon USB MkII. AC3/DTS passthrough worked fine on it back on Windows XP
Receiver: Yamaha DSP-AX2. Old but works fine with AC3 and DTS from a variety of sources including this card on XP, the onboard sound on various PCs and various other sources of AC3 and DTS such as a PS3, DVD Player etc.
Randomly when starting a video from the Pi, the stream will apparently not get marked as AC3 or DTS, and there will be this horiffic screeching or hissing. During this the amp will continue to say PCM: PRO-LOGIC so I think that whatever header is necessary to get these streams working is not getting sent, or is getting sent incorrectly.
You can stop the video and start it again and most of the time it will be fine. Sometimes it takes two or three attempts.
Any ideas?