[alsa-devel] Warning/error from ALSA’s pcm_min.c example. Possible problem?

[Raymond Yau]

>> On Sat, 30 Jan 2010, Louise Hoffman wrote:

>> Dear ALSA developers,
>>
>> When I compile ALSA's pcm_min.c[0] example with
>>
>> gcc -Wall -lasound pcm_min.c -o pcm_min
>>
>> Everything is fine, but running it, I get the white noise as expected,
>> but I also get this warning/error:
>>
>> Short write (expected 16384, wrote 7616)

>It was a bug in alsa-lib. I fixed it in patch bellow. Thank you for your
>report.

> http://git.alsa-project.org/?p=alsa-lib.git;a=commitdiff;h=2e48439ad93f6c8d99a2d72928ac71285b5211bb <http://git.alsa-project.org/?p=alsa-lib.git;a=commitdiff;h=2e48439ad93f6c8d99a2d72928ac71285b5211bb>

Add snd_pcm_dump() after call snd_pcm_set_params in pcm_min.c

The start threshold is equal to buffer size , so there should be a
short write at the second write since
16384 + 7616 = 24000  ( start threshold )

your patch had changed the behaviour


 ./pcm_min
ALSA <-> PulseAudio PCM I/O Plugin
Its setup is:
  stream       : PLAYBACK
  access       : RW_INTERLEAVED
  format       : U8
  subformat    : STD
  channels     : 1
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 8
  buffer_size  : 24000
  period_size  : 6000
  period_time  : 125000
  tstamp_mode  : NONE
  period_step  : 1
  avail_min    : 6000
  period_event : 0
  start_threshold  : 24000
  stop_threshold   : 24000
  silence_threshold: 0
  silence_size : 0
  boundary     : 1572864000
state = 2
write 16384 frames
state = 2
write 16384 frames
state = 3
write 16384 frames
state = 3
write 16384 frames
state = 3