2010/5/20 Tyler Conant tconant@taser.com
I'm trying to use dmix on an OMAP processor. I'm experiencing the first 50 ms of the sample getting clipped. When I aplay directly to the hw:0 I don't get the clipping. The difference I see between the alsa configuration between dmix and hw:0 is the start_threshold, stop_threshold and silence_size. When it's direct to hw:0 the start and stop threshold are equal to the buffer size. For dmix the start threshold is 1 and the stop threshold is 1445199872. Is this dmix which is setting the start and stop or is this aplay. I'm only guessing this is the reason why the first part is clipping. The only bug which seem similar is http://bugs.gentoo.org/show_bug.cgi?id=218641 and it's already been closed out. I'm using alsa lib 1.0.23
with hw:0
Audio_Prompts # aplay -v -D hw:0 Click03.wav Playing WAVE 'Click03.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Mono Hardware PCM card 0 'TWL4030' device 0 subdevice 0 Its setup is: stream : PLAYBACK access : RW_INTERLEAVED format : S16_LE subformat : STD channels : 1 rate : 44100 exact rate : 44100 (44100/1) msbits : 16 buffer_size : 22052 period_size : 5513 period_time : 125011 tstamp_mode : NONE period_step : 1 avail_min : 5513 period_event : 0 start_threshold : 22052 stop_threshold : 22052 silence_threshold: 0 silence_size : 0 boundary : 1445199872 appl_ptr : 0 hw_ptr : 0 /opt/axonapp/Audio_Prompts #
With dmix:
/Audio_Prompts # aplay -v Click03.wav Playing WAVE 'Click03.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Mono Plug PCM: Direct Stream Mixing PCM Its setup is: stream : PLAYBACK access : RW_INTERLEAVED format : S16_LE subformat : STD channels : 1 rate : 44100 exact rate : 44100 (44100/1) msbits : 16 buffer_size : 22052 period_size : 5513 period_time : 125011 tstamp_mode : NONE period_step : 1 avail_min : 5513 period_event : 0 start_threshold : 22052 stop_threshold : 22052 silence_threshold: 0 silence_size : 0 boundary : 1445199872 Hardware PCM card 0 'TWL4030' device 0 subdevice 0 Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S16_LE subformat : STD channels : 1 rate : 44100 exact rate : 44100 (44100/1) msbits : 16 buffer_size : 22052 period_size : 5513 period_time : 125011 tstamp_mode : ENABLE period_step : 1 avail_min : 5513 period_event : 0 start_threshold : 1 stop_threshold : 1445199872 silence_threshold: 0 silence_size : 1445199872 boundary : 1445199872 appl_ptr : 0 hw_ptr : 0 /opt/axonapp/Audio_Prompts #
asound.conf: pcm.dmixer { type dmix ipc_key 2048 ipc_key_add_uid true slave {
channels 1 pcm hw:0 rate 44100 period_time 125011 period_size 5513 buffer_size 22052} }
pcm.asymed { type asym playback.pcm "dmixer" capture.pcm "hw:0,0" }
pcm.!default { type plug slave.pcm "asymed" }
The major difference is access : MMAP_INTERLEAVED