This problem is something I have been stuggling with the last few days. The project I am doing (for school) involves making a music player with VGA output and keyboard input. Audio is supplied on a SD card in a WAV format(48k, 16-bit, 2 channels).
Everything works, except audio. I can read data from the SD card and get the bytes that make up the wavefiles. But how to correctly send them to the audio chip has puzzled me. In used both alt_up_audio_write_fifo and alt_up_audio_play_l (and r respectively). Used both pointers and content. Still the sounds remains distorted. There is a remote resemblence to what it the file sounds like on a PC. So I know I have the correct data. Just the trick of actually getting the data correctly the audio device using the above named functions. That latter is what I have been struggling with.
