[alsa-devel] ASoC: mmap or read/write?

Prasant J pj0585 at gmail.com
Fri Oct 19 11:36:34 CEST 2012

On Fri, Oct 19, 2012 at 2:28 PM, Clemens Ladisch <clemens at ladisch.de> wrote:
> Mike Looijmans wrote:
>> From: Prasant J <pj0585 at gmail.com>
>>>> Prasant J wrote:
>>>>> I'm writing an alsa application for recording & playing 16 channel audio.
>>> I'm working with Beaglebone (ARM Cortex-A8 720 MHz). (Currently
>>> failures are for 8 channels 32 bit / 16 bit, but our final target is
>>> 16 channels)
>>> I have managed to get Audio capture working fine (after certain linux
>>> optimizations) but playback is giving under-runs (only when PLAYBACK &
>>> CAPTURE run together)
>> You must be doing something wrong. I'm doing 32-bit, 16-channel input
>> at 51.2kHz on a OMAP-L138 (an ARM9 CPU at 450 MHz)

I'm playing & recording at the same time, that should be the reason.

When I was using arecord (only capture) I was getting overruns and
only after making some linux optimizations, I was able to record
properly. Are you 100% sure you do not observe any errors? Did you do
tests for longer durations?

> Playback and capture at the same time seems to be harder for certain
> embedded devices.  I don't know if this is a driver bug or a hardware
> limitation.

The bottle-neck is SD card access. Driver bug cannot be ruled out, but
it is difficult to evaluate.

Regards, Praant

P.S.: How do I reply to a post whose mail I did not receive. (I have
enabled alsa-devel mails only now, but if someone does not include me
in cc, I do not receive the posts started by me)

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