linux-kernel - Re: Possible bug, with extreme low latency audio.

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Message-id: <op.vrqe79rh6426ze@millennium>
Date:	Wed, 02 Mar 2011 21:01:11 +0100
From:	Uwaysi Bin Kareem <uwaysi.bin.kareem@...adoxuncreated.com>
To:	linux-kernel@...r.kernel.org, clemens@...isch.de
Subject: Re: Possible bug, with extreme low latency audio.

On Wed, 02 Mar 2011 08:28:50 +0100, Clemens Ladisch <clemens@...isch.de>
wrote:

> Uwaysi Bin Kareem wrote:
>> The other is a firewire device (Konnekt24d using FFADO, running on the  
>> old
>> firewire stack).
>> The firewire device actually plays nicely without much buffer underruns
>> down to 0.363 ms latency (8x2 @ 44.1k).
>
> FireWire packets are sent every 125 µs; for audio, every packet contains
> either zero or eight samples, and the proportion of data and no-data
> packets is adjusted so that the overall rate is 44100 samples per
> second.  So 8x2 is the theoretical minimum.
>
>> However it seems to choke at 8x2 @ 96k.
>
> At sample rates above 48 kHz, there are 16 samples per packet (and above
> 96 kHz, 32).  It is not possible to use 8x2 at 96 kHz, and FFADO should
> not have allowed you to try it; please file a bug there:
> <http://subversion.ffado.org/report> (requires a login).
>
Ok, I am hitting the hardware limits. I'll inform FFADO crew about this.  
There are probably more bound to hit this limit, as lowlatency operation  
with Linux, is getting this good. A good error msg with the above  
information, would be good.

Best Regards,
Uwaysi.

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