Please let me know if my below understanding is correct :
snd_pcm_sw_params_set_start_threshold() explains : "PCM is automatically started when playback frames available to PCM are
= threshold or when requested capture frames are >= threshold"
PCM has below states :
SND_PCM_STATE_OPEN Open SND_PCM_STATE_SETUP Setup installed SND_PCM_STATE_PREPARED Ready to start SND_PCM_STATE_RUNNING Running SND_PCM_STATE_XRUN Stopped: underrun (playback) or overrun (capture) detected SND_PCM_STATE_DRAINING Draining: running (playback) or stopped (capture) SND_PCM_STATE_PAUSED Paused SND_PCM_STATE_SUSPENDED Hardware is suspended SND_PCM_STATE_DISCONNECTED Hardware is disconnected
When ever underrun occurs, PCM device state goes to XRUN state. To bring back the PCM playback device to playback {Ready to start}, we use snd_pcm_prepare().
*Thus snd_pcm_sw_params_set_start_threshold() should again prebuffer(threshold) X periods of data {which we have set in software params}, once again after the XRUN state is recovered.*
Thanks and regards, Irfan
On 10/29/2012 04:50 PM, irfanks wrote:
Hello,
snd_pcm_sw_params_set_start_threshold() API descriptionexplains, "PCM is automatically started when playback frames available to PCM are >= threshold"
I want to know, whether above pre-buffering(threshold)mechanism is only during the start of playback ? OR Also if my playback device goes to XRUN state, Again next time when i prepare my playback device using snd_pcm_prepare(). Again the prebuffering (threshold) will occur since i have set snd_pcm_sw_params_set_start_threshold() to N periods in software params.
Best Regards, Thanks in advance, Irfan...