[alsa-devel] Measuring Device Throughput - MMAP vs. RW

[Pavel Hofman]

On Tue, Sep 10, 2019 at 9:18 AM Takashi Iwai <tiwai at suse.de> wrote:

>
> The value read from snd_pcm_status() should give the accurate pair of
> the position and the timestamp.
>
Thanks. IIUC, if I call snd_pcm_status() in that mmap_commit method, get
data between e.g. 10 seconds, and divide the increase of status._ptr
https://github.com/michaelwu/alsa-lib/blob/afb2fbd0e554e42e51325c3197a176ea96a74203/include/sound/asound.h#L422
by increase of status.tstamp, I should get the the most precise available
soundcard rate estimate referenced to system time.



> You need to check the delay count as
> well, which compensates the in-flight samples.
>
>
I need just the rate at which the soundcard consumes/produces samples, I do
not care about time at which the sound is being produced. I do not know
exact meaning of the delay field. Is it involved in this calculation?
Please is there any exact detailed description of the status fields?

Thanks.

Pavel.