Re: [LAU] Many identical cards - how to keep them straight

From: Pieter Palmers <pieterp@email-addr-hidden>
Date: Mon Mar 10 2008 - 17:23:44 EET

Arnold Krille wrote:
> Am Montag, 10. März 2008 schrieb Mark Knecht:
>> And let's not drop out 1394 or other external buses. The issue isn't
>> USB as much as it's an external network of devices that can both be
>> rewired easily and in some cases come and go in strange ways. If
>> you're using an external USB powered hub, for instance, and the power
>> isn't applied for some period of time the system thinks the device is
>> gone when it's just that someone kicked out the wall wart. Making that
>> sort of support of external devices really robust would take some
>> serious thinking.
>
> The way ffado works, these will all be joined (possibly automatically) in one
> big device. and each channel on each device is named unique(?) and aliased
> with system_*. So it should be the same ports in jack everytime you start the
> setup.
The device combining is optional. Well, at least when FFADO is released
it will be. Currently it indeed grabs all devices it can find and
combines them into one device. But preventing that is not very difficult.

The reason to do the combining in ffado itself is that doing so ensures
absolute phase alignment between devices. Or at least in theory it should.

The nice thing about firewire devices is that they all have a unique ID,
hence it's not very difficult to distinguish between them. FFADO will
have a method to specify this ID to select a device. It also makes it
easier to provide a consistent view of a combined device. Currently
ffado sorts the devices on GUID before combining them, such that the
jack port to physical channel mapping is always consistent.

>
> But I don't think ffado is currently able to do dynamic add/remove. Can't test
> it here, not enough fw-devices. ;-)
Dynamic add/remove? not really no. You'll have to restart jackd for that.

Greets,

Pieter
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Received on Mon Mar 10 20:15:03 2008

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