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Subject: Re: pcm_set_frequency is ignored

Re: pcm_set_frequency is ignored

From: Christian Gmeiner <>
Date: Sun, 31 Aug 2008 15:56:40 +0000

2008/8/31 Joseph Garvin <>:
> On Sun, Aug 31, 2008 at 3:05 AM, Magnus Holmgren <> wrote:
>> Joseph Garvin wrote:
>>> To shrink my plugin size I'm trying to convert my sound samples to be
>>> 22050hz instead of 44100. But when I do this the sound always plays too fast
>>> like a chipmunk. I'm calling pcm_set_frequency(22050) but no matter what
>>> number I give it (I tested crazy values like 100) I get the same result. It
>>> always tries to play at 44100hz. I'm trying on the Sansa e200 simulator. Is
>>> this a limitation of the simulator or maybe of the e200? If so it'd be nice
>>> to get some sort of console warning.
>> pcm_set_frequency sets the frequency of the hardware, but it is usually
>> quite limited in what frequencies it supports. Try dsp_configure, using
>> DSP_SWITCH_FREQUENCY, to set the frequency. See the mpegplayer audio thread
>> for an example.
> I tried:
> struct dsp_config* dsp = (struct dsp_config *)rb->dsp_configure(NULL,
> rb->dsp_configure(dsp, DSP_SWITCH_FREQUENCY, 22050);
> rb->pcm_set_frequency(22050);
> rb->pcm_apply_settings();
> But this still had no effect, at least in the simulator. Do I need to use
> dsp_process somehow? It's unclear to me how it works. I'm still playing the
> sound with pcm_play_data.

The uisimulator is not using rockboxs dsp yet, I have here some basic
code to use the dsp for bass, treble settings. The
frequency stuff is on todo for the audioapi. Maybe I will find some
time to commit some stuff during the coming week.

BSc, Christian Gmeiner
Received on 2008-08-31

Page was last modified "Jan 10 2012" The Rockbox Crew