Subject: Re: [linux-audio-dev] Re: [Alsa-devel] Fwd: Re: USB Quattro Linux support
From: Reynald Hoskinson (bean_AT_openface.ca)
Date: Mon Apr 15 2002 - 21:59:57 EEST
If there is a project to add alsa support for these cards, I'd like to
help out. I have a USB Duo. Has anybody asked for the specs yet?
cheers,
reynald
Paul Davis wrote:
>>>I think a more exact description of the gphoto approach is:
>>>application<->gphoto-lib<->usb-lib<->low-level-generic-USB driver.
>>>
>>>Only the low-level kernel USB drivers and the usbdevfs filesystem are in
>>>kernel space, beyond that the hardware driving is done via the user-space
>>>libusb. I'm not sure whether this would have low-enough latency for audio
>>>use, after all, digital cameras aren't timing-critical for the sort of things
>>>that gphoto aims to do.
>>
>
> If usb-lib is written properly and low-level-generic-USB-driver is
> written correctly, there are no latency issues. Latency issues don't
> arise from the number of layers of code unless one of the layers of
> code is astonishingly badly written. They arise from designs that
> buffer data along the way or delay execution of a thread. The system
> outlined above doesn't inherently have any such problems.
>
>
>>I think that there is support in gphoto for capturing video streams but I have
>>n't used it so I don't know if that is correct. Anyway if I am correct then la
>>tency issues would have been solved already.
>
>
> Not at all. arecord(1) can capture audio, but it can't capture 26
> channels of audio at 64 frames/interrupt. Handling latency is partly
> an application issue, partly a kernel issue, and partly a requirement
> that libraries in the way don't get in the way. It has very little to
> do with whether you can do certain generic tasks or not.
>
> --p
>
>
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