Re: [linux-audio-dev] Low Latencies. Which hardware to use?

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Subject: Re: [linux-audio-dev] Low Latencies. Which hardware to use?
From: Paul Davis (pbd_AT_Op.Net)
Date: Tue Jun 12 2001 - 00:40:25 EEST


>> I have a trident-based hoontech card that I can run quite happily at
>> 64 frames. My Tropez+ is a bit more problematic at 64 frames - the two
>> streams don't seem to run precisely in sync with each other all the
>> time. I don't know if this a h/w problem or a design problem.
>
>So what kind of buffer settings are you using with alsa? Reading the
>source the alsa xg driver seems to allow 64 frames fragment size, but

the same as usual (_frames_per_cycle = 64 in the code below):

        if ((err = snd_pcm_hw_params_set_periods (handle, hw_params, 2, 0)) < 0) {
                error << "ALSA: cannot set fragment count minimum to "
                      << 2
                      << " for " << stream_name
                      << endmsg;
                return -1;
        }

        if ((err = snd_pcm_hw_params_set_period_size (handle, hw_params, _frames_per_cycle, 0)) < 0) {
                error << "ALSA: cannot set fragment length to "
                      << _frames_per_cycle
                      << " for "
                      << stream_name
                      << endmsg;
                return -1;
        }

        if ((err = snd_pcm_hw_params_set_buffer_size (handle, hw_params, 2 * _frames_per_cycle)) < 0) {
                error << "ALSA: cannot set buffer length to "
                      << 2 * _frames_per_cycle
                      << " for " << stream_name
                      << endmsg;
                return -1;
        }

>I have a dual machine, too. Are all your soundcards pci btw? My SB AWE
>is ISA, maybe that's the problem? I think I'll get myself the

RME, Trident: PCI
Tropez+: ISA

>new RME card with multiface. Paul: How about writing a driver together?
>At least it seems that this card is already available in germany. Do you
>think RME would actually provide hardware for writing a driver or do
>I still have to purchase it :)

RME need to provide the specs. They have told me they will do this
once the card is available. I expect the driver to be an extension to
the existing digi9652 driver, not a new one. They have provided me
with h/w in the past.

--p


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