Has anyone had any success using the KEIL USB audio class application as a starting point for a a 24 bit audio device. I've made the obvious changes to the enumeration structure of the application code (ie bSubFrameSize=3, bBitResolution=24, wMaxPacketSize=128)and the changes to the audio definitions (P_S=64). And thats it for changes.
I am able to verify that recieved packet size is increased as expected (from 64 to 96 bytes). I can verify data received is reasonable and plays on MCB2300/LPC2378 kit speaker relatively distortion free. But a couple of things aren't working as they should.
1: When I play a 24 bit data file, I do see the 24 bits of "data", but only 16 of the bits are actual audio data, the other 8 are padded with zeroes.
2: Also the order of the bytes isn't correct. The 16 bits of audio data are the most significant two bytes and the padding byte is the lowest (not an endian issue)
I've run two different media players on Windows XP: Windows Media Player and AIMP2(32 bit processing). The USBaudio.sys USB driver is installed.
Any insight into what I am seeing is appreciated.
Thanks, Ed