HDMI audio choppy/distorted with ALSA

[bhokaal]

Hi,
I have ATI AMD video card HD7770 with HDMI o/p i use. I am able to get sound but its very very choppy/distorted. The strange fact is output works perfectly with default Pulse audio settings (no distortion/choppiness) . Since ALSA sounds better has better support for bit streaming i am very interested to get native ALSA running. Things i have already tried

1. Completely removing/stopping pulse audio the alsa choppiness/distortion still remains
2. I have tried both fglrx & opensource radeon driver with same result
3. So basically when a stream plays through default pulse audio its perfect but when directly through ALSA its distorted. to see the difference i recorded the info in cat /proc/asound/card1/pcm3p/sub0/* in both the cases the major difference in o/p was

access: MMAP_INTERLEAVED >>>pluse audio
access: RW_INTERLEAVED >>> native alsa

Is there a way to force mmap mode in native alsa or any other idea ??
If you can suggest a better place to pose this query please ??
_________________
--
Enjoy
Bhokaal