On 10/19/2012 11:36 AM, Prasant J wrote:
On Fri, Oct 19, 2012 at 2:28 PM, Clemens Ladisch clemens@ladisch.de wrote:
Mike Looijmans wrote:
From: Prasant J pj0585@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)
@Mike: I'm playing & recording at the same time, that should be the reason.
Good point, my board only a has a single playback channel.
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?
I've had it running for about an hour, using /dev/null as a target because I don't have enough memory to store that much data.
I did get lots of underruns/overruns while getting started, but they turned out te be related to clock configurations. So take a really good look at those, the way the registers are being set are often very obscure and register defines often don't match the datasheet.
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.
@Clemens: The bottle-neck is SD card access. Driver bug cannot be ruled out, but it is difficult to evaluate.
Sound familiar, on my board a USB SD cardreader connected to the USB port was actually faster than the built-in 4-wire SD.
Mike.
Met vriendelijke groet / kind regards,
Mike Looijmans
TOPIC Embedded Systems Eindhovenseweg 32-C, NL-5683 KH Best Postbus 440, NL-5680 AK Best Telefoon: (+31) – (0)499 - 33.69.79 Telefax: (+31) - (0)499 - 33.69.70 E-mail: mike.looijmans@topic.nl Website: www.topic.nl
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