Hi Guys,
I have been using the alsa api for a while working on some multimedia
stuff.
I believe I have found a bug with the intel8x0 driver when running the
nforce chip-set.
The problem appears to be an uninitialized variable type problem. The
first time you call snd_pcm_mmap_begin() the channels are returned in
their pairs in a random order. That is the rear channels may end up in
the front or Center/LFE slots, etc, the channel order does not change
from then on.
I compiled up the pcm.c test code and tried that out. This shows the
problem, only worse. If you change the generate_sine function to the
following to pick out one pair of channels only.
if ((chn == 2) || (chn == 3))
*samples[chn] = ires;
else
*samples[chn] = 0;
then call pcm with the following...
./pcm -r 48000 -c 6 -m direct_noninterleaved
I would expect silence from all but the rear pair. What we get is a
sequencing of the audio through the 6 channels. It makes no difference
which of the modes or rates I use.
Am I just misusing the api or is this a bug?
Here are the hardware specs.
ShuttleX pc
North bridge-Nvidia nForce2, South bridge-nVidia MCP-T
Realtek ALC650 6 Ch, Support Digital SPDIF Output
for more details on hardware.
http://www.us.shuttle.com/specs_access.asp?pro_id=284
running Mandrake Linux 9.0.
I have tested several of the alsa releases and am currently using 0.9.6.
Richard Lemon.
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