On Wed, 17 Sep 2003, James Courtier-Dutton wrote:
Output from sending stereo sound to the "dmix" device. bash-2.05b# cat status state: RUNNING trigger_time: 1063822024.640173000 tstamp : 1063822060.456968000 delay : -1719463 avail : 1731463 avail_max : 1731463 ----- hw_ptr : 1719463 appl_ptr : 0 bash-2.05b#
Output from sending stereo sound to the "front" device. bash-2.05b# cat status state: RUNNING trigger_time: 1063823309.038609000 tstamp : 1063823320.869677000 delay : 14161 avail : 2223 avail_max : 3586 ----- hw_ptr : 567983 appl_ptr : 582144
As you can see, the "front" device acts correctly, with all the pointers acting as they should. But with "dmix", all the pointers are wrong. This is particularly problematic for me, as I need a properly functioning "delay" value for my application.
This is using alsa from 2.6test5 kernel.
This is absolutely ok. The device is running in no-xrun mode, because multi-applications have access to it. The dmix plugin has own hw_ptr and appl_ptr for each instance and mangles the information from kernel to correct values to follow the ALSA API.
What is your problem? The resolution of the dmix plugin is always one period (to make things faster), but it's not a problem to add the slow calls.
Jaroslav
----- Jaroslav Kysela <[EMAIL PROTECTED]> Linux Kernel Sound Maintainer ALSA Project, SuSE Labs
The problem is that my application relies on a correct "delay" value, so that it can use it to keep sound/video in sync.
An example of more status output while playing a .wav file with aplay -D dmix. Each "cat status" is typed in quickly after each other.
bash-2.05b# cat status state: RUNNING trigger_time: 1063888806.325296000 tstamp : 1063888809.954270000 delay : -174225 avail : 186225 avail_max : 186225 ----- hw_ptr : 174225 appl_ptr : 0 bash-2.05b# cat status state: RUNNING trigger_time: 1063888806.325296000 tstamp : 1063888810.491712000 delay : -200026 avail : 212026 avail_max : 212026 ----- hw_ptr : 200026 appl_ptr : 0 bash-2.05b# cat status state: RUNNING trigger_time: 1063888806.325296000 tstamp : 1063888811.036897000 delay : -226198 avail : 238198 avail_max : 238198 ----- hw_ptr : 226198 appl_ptr : 0
As you can see, the sound is being played, and comes out of the speakers, and there are no xruns, because if there were I would hear them.
For the "dmix" device.
As the buffer size is 12000, avail/avail_max should never reach a value > buffer_size.
delay should never reach a size > buffer_size (12000).
My guess is that delay = appl_ptr - hw_ptr, and thus the reason for it being negative.
Cheers James
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