Re: [FFADO-user] iLink firewire audio?

[Stefan R. <st...@s5...>]

On Apr 22 Erich Boleyn wrote:
> [please reply to me specifically as I'm not on the email list right now]
> 
> I apologize if this is a newbie question which others deem obvious, but I
> could not find anything relevant in the email lists.
> 
> Will (or at least "Could") the FFADO driver project work with an
> iLink-enabled Home Theatre amplifier?
> 
> I see various individual devices listed, but I'm not quite sure if these
> are controlled more in the sense of, say:
>   --  a PCI-style driver, with devices and registers that must be
>         programmed uniquely to each device.
> OR
>   --  a USB-style "generic" driver, but many of them have quirks or
>         extension features.

It is a combination of both, unfortunately.  FireWire storage, networking,
and almost all video devices are using just one or two open protocol
standards, whereas FireWire audio is a mess of a whole lot of different
protocols, most of them proprietary, together with varying device
capabilities and quirks.

> ...Or is there an "iLink" protocol which is fundamentally different from
> what the FFADO driver stack does?
> 
> Yeah yeah, some have told me to "just buy a newer amp and use HDMI", but
> most of the HDMI drivers in Linux suck, and many have problems with requiring
> video to be active/a monitor/TV turned on.

"iLink" does not refer to a specific audio streaming and control
protocol.  It is merely Sony's term for IEEE 1394 (the generic term for
the bus and its low-level on-the-wire protocol) or FireWire (Apple's term).

A consumer audio amplifier with IEEE 1394/ iLink port probably implements
IEC 61883 and AV/C style audio streaming and control, for which there is
support in FFADO as far as I understand.  So, getting it to work with
FFADO may be as easy as adding device identifiers to
~/.ffado/configuration or /usr/[local/]share/libffado/configuration.

It cannot be made to work though if this amplifier only offers audio
playback but no audio capture through its iLink port.  FFADO is designed to
maintain two streams (in and out) to each connected audio device.

But there is an alternative now:  Kernel 2.6.39 contains an ALSA driver
for two playback-only consumer audio devices, LaCie FireWire Speakers (a
stereo device) and Griffin FireWave (a 6 channels device).  It may be
possible to expand this driver for such an amplifier as well.

At the moment, kernel 2.6.39 is available as -rc5 prerelease.  The
snd-firewire-speakers driver can also be patched into older kernels,
e.g. with patches from http://user.in-berlin.de/~s5r6/linux1394/updates/.
There are 2.6.39 kernel packages for some distributions available, but you
would have to build the kernel from source anyway because the
snd-firewire-speakers source would have to be edited to recognize device
IDs and perhaps to take some other device properties into account.

Author of this FireWire ALSA driver is Clemens Ladisch who I Cc'd.
-- 
Stefan Richter
-=====-==-== -=-- ====-
http://arcgraph.de/sr/