alsa-project/alsa-utils pull request #200 was opened from iam-TJ:
I encountered this issue whilst researching a bug in capture handling in ALSA/PulseAudio/PortAudio/Audacity. When recording for a fixed duration the duration is measured by the quantity of samples, not clock time. In `capture()` a call to `calc_count()` occurs before `set_params()`, but in that latter function the actual sample rate used may differ from the requested rate , but the count is not recalculated. E.g:
```
$ time arecord -D hw:1,0 -d 2 -c 2 -f S16_LE -r 384000 --dump-hw-params /tmp/test.11.wav
Recording WAVE '/tmp/test.11.wav' : Signed 16 bit Little Endian, Rate 384000 Hz, Stereo
HW Params of device "hw:1,0":
--------------------
ACCESS: MMAP_INTERLEAVED RW_INTERLEAVED
FORMAT: S16_LE S32_LE
SUBFORMAT: STD
SAMPLE_BITS: [16 32]
FRAME_BITS: [32 64]
CHANNELS: 2
RATE: [44100 192000]
PERIOD_TIME: (83 11888617)
PERIOD_SIZE: [16 524288]
PERIOD_BYTES: [128 2097152]
PERIODS: [2 32]
BUFFER_TIME: (166 23777234)
BUFFER_SIZE: [32 1048576]
BUFFER_BYTES: [128 4194304]
TICK_TIME: ALL
--------------------
Warning: rate is not accurate (requested = 384000Hz, got = 192000Hz)
please, try the plug plugin
real 0m4.009s
user 0m0.004s
sys 0m0.007s
```
In this example, because the actual sample rate was 1/2 of that requested, count is double what it should be and therefore the recording continues for 4 seconds instead of the requested 2 seconds.
Moving the call to `set_params()` to before the count logic solves it:
```
$ time aplay/aplay -C -D hw:1,0 -d 2 -c 2 -f S16_LE -r 384000 --dump-hw-params /tmp/test.11.wav
HW Params of device "hw:1,0":
--------------------
ACCESS: MMAP_INTERLEAVED RW_INTERLEAVED
FORMAT: S16_LE S32_LE
SUBFORMAT: STD
SAMPLE_BITS: [16 32]
FRAME_BITS: [32 64]
CHANNELS: 2
RATE: [44100 192000]
PERIOD_TIME: (83 11888617)
PERIOD_SIZE: [16 524288]
PERIOD_BYTES: [128 2097152]
PERIODS: [2 32]
BUFFER_TIME: (166 23777234)
BUFFER_SIZE: [32 1048576]
BUFFER_BYTES: [128 4194304]
TICK_TIME: ALL
--------------------
Warning: rate is not accurate (requested = 384000Hz, got = 192000Hz)
please, try the plug plugin
Recording WAVE '/tmp/test.11.wav' : Signed 16 bit Little Endian, Rate 192000 Hz, Stereo
real 0m2.009s
user 0m0.001s
sys 0m0.008s
```
Request URL : https://github.com/alsa-project/alsa-utils/pull/200
Patch URL : https://github.com/alsa-project/alsa-utils/pull/200.patch
Repository URL: https://github.com/alsa-project/alsa-utils
