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Subject: Questions about PortalPlayer based architectures and PDBox

Questions about PortalPlayer based architectures and PDBox

From: Wincent Balin <>
Date: Mon, 05 Jul 2010 01:41:35 +0200

 Dear fellow Rockbox developers,

I have questions about PortalPlayer (and generally all ARM-) based
player architectures.

I had begun the developemtn of PDBox on an iRiver H300, which is a
big-endian, Coldfire based, rather straightforward architecture. As I
tried to include support for other, mostly PortalPlayer based
architectures, I did encounter a number issues, some of which are a
small nuisance, and others are quite heavy.

I tried PDBox on iPod 3G (simulator only) and on SanDisk e200 (both in
the simulator and on the real player).

The first error which was immediately recognized was playng sound with
double frequency. Are PortalPlayer based targets hardwired to the sample
rate of 44100? When I sat the constant PD_SAMPLERATE to 44100 in the
file pdbox.h, the simulator played all sounds correctly.

I tried then to differ between sampling rate needed for PortalPlayer and
all others, but

#ifdef CPU_PP
  #define PD_SAMPLERATE 44100
  #define PD_SAMPLERATE 22050

did not work -- the sample rate remained at 22050; it seems that CPU_PP
did not exist. I include plugin.h on top of pdbox.h.

So my question is basically:

Is it possible to run sound output on PortalPlayer based targets with
sampling frequency of 22050 Hz? Or at least 32000 Hz?
And if so, how can it be specified in pdbox.h?

Sincerely yours,

                                     Wincent Balin

P.S.: There are further errors, as no of the original Pure Data designs
used for testing did work, meaning that not a single one of them
produced sound. This may be the consequence of the bug described above.
Furthermore, pdpod_drums.pd does not draw widgets in the GUI and
pdpod_l8p.pd crashes with Division through zero error. But in my opinion
the first error to solve should be the one about sample frequency.
Received on 2010-07-05

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