Jeffrey Barish wrote:
> I have some sound files which were playing at the wrong sample rate (the pitch
> was about a step high and the speed was elevated). The sample rate of the
> files is 88.2 kHz. I believe that they were playing at 96 kHz, judging from
> the pitch error. My output device is HDA Intel PCH.
>
> I found that I could fix the problem by augmenting my /etc/asound.conf file with
> a rate specification:
>
> pcm.!default {
> type hw
> card 0
> rate 192000
> }
>
> However, I do not understand what this change actually does.
That device now claims that its only supported rate is 192 kHz.
> When I play one of the sound files now and then do
>
> cat /proc/asound/card0/pcm0p/sub0/hw_params
>
> I see that rate is 192000. In fact, I see that same value for rate regardless
> of the sample rate of the sound file.
When a player program tries to play something with another rate, it must
choose between aborting with an error, or resampling to that rate.
> I understood that "type hw" meant that ALSA would send a file directly
> to the sound device without any processing, so why is the conversion
> happening and where?
If you had a "plughw" device, ALSA would be able to do the resampling.
With "hw", the player program must use its own resampler (if it has one).
> When I run the command
>
> speaker-test -D hw:CARD=PCH,DEV=0 -c2 -r 48000
>
> the sample rate that I read in hw_params corresponds to the value I specify in
> the command -- except when I specify 88200, which produces an "invalid
> argument" error.
Strange.
What is the output of this command:
aplay -D hw:0 -t raw -f dat -r 88200 -d 3 -v /dev/zero
Regards,
Clemens
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