2011/3/9 Jaroslav Kysela perex@perex.cz
On Wed, 9 Mar 2011, Jean-Yves Avenard wrote:
Hi
On Wednesday, 9 March 2011, Raymond Yau superquad.vortex2@gmail.com wrote:
hda-intel.c only allocate 64Kbytes
/* buffer pre-allocation */ snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG, snd_dma_pci_data(chip->pci), 1024 * 64, 32 * 1024 * 1024);user or distribution need to change "prealloc" from 64 to a higher value for getting 500ms buffer
echo 1024 > /proc/asound/Intel/pcm0p/sub0/prealloc
It seems you misunderstood my first message.
For a start, the default memory allocated to alsa in ubuntu is 4096kB. so the amount of ram isn't the problem.
Setting a buffer of 200ms: ok 300ms: ok 400ms: not ok (invalid argument) 500ms: ok
Why would 400ms gives invalid argument, when 500ms doesn't nor 300. Memory available is obviously not the issue.
If only 64kB is allocated, requesting 200ms gives you 200ms 300ms -> 300ms 400ms -> invalid argument 500ms -> 371ms 600ms -> 371ms
You would assume that requesting 400ms would work or return what can fit in what has been pre-allocated.
What is your dir argument (last one) for the near functions? If it's NULL or value is zero, it means you request the exact value which may not be available. Use -1 to request specified or smaller value or 1 to request specified or bigger value.
Take another example from alsa-lib/test
Try many parameters but still cannot let alsa-lib/test/latency.c work with alsa-pulse plugin and latency stop without any error message
alsa-lib/test/latency -P pulse -C pulse
adding some debug statement and find that it alway fail in setparams()
if (*bufsize > latency_max) { + printf("*bufsize %d > latency_max %d\n",*bufsize,latency_max); return -1; }