Re: [Jack-Devel] Very low latency audio

On 09/20/13 14:53, Harry van Haaren wrote:

>> On my netbook, I was able to start jackd with
>> jackd -P62 -dalsa -dhw:0 -r44100 -p16 -n2
>> but the hardware driver didn't support -p8 or -p4.
>>
> Indeed very few cards support that low buffer size: apparently one of
> the Creative SoundBlaster series starts on -p8 but xruns internally...
> I've heard that some RME gear is capable of running at such low
> latencies too. No experience with those RME interfaces (the PCI-E
> stuff IIRC).

The RME PCI cards do 64, while their PCIe counterparts offer 32.


If you want less, then you have to sample the hardware pointer and write
closely in front of it. In theory, pulseaudio already supports it on
Intel HDA cards, but they're aiming for less interrupts/Wakeups, not low
latency.

I have an experimental kernel patch to enable the same mode on RME HDSPM
cards, but pulseaudio has a built-in limit of 2x32 channels, so I cannot
test it on my 2x36 channels RayDAT. ;) Maybe I could try with the 2x18
channels Multiface attached to my laptop, just to see if it works.



IIRC, Clemens Ladisch successfully used small buffers with his firewire
ALSA module, but I don't remember the exact numbers.



Just my €0.02

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