freebob i/o port latency patch

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freebob i/o port latency patch

Jesse Chappell
While testing the freebob backend I noticed that it wasn't setting the
port latencies on the interface's ports.  In addition it didn't
support the -I and -O parameters which let users specify systemic
extra latency.  The attached patch provides both.  For those who might
not know, Ardour uses these value in order to do latency compensation.

Pieter, I know the implementation in the freebob driver introduces
extra buffering in the 1394 stuff, and these values (if known) should
be added to the port latency assignment.  Otherwise, users have to
measure it (with jdelay or something) and account for it with the
systemic latency params.

Also attached (attn Rui) is the patch to make qjackctl let you use these params.

jlc

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jack_freebob_iolat.patch (6K) Download Attachment
qjackctl_freebob_iolat.patch (2K) Download Attachment
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Re: freebob i/o port latency patch

Pieter Palmers
Jesse Chappell wrote:

> While testing the freebob backend I noticed that it wasn't setting the
> port latencies on the interface's ports.  In addition it didn't
> support the -I and -O parameters which let users specify systemic
> extra latency.  The attached patch provides both.  For those who might
> not know, Ardour uses these value in order to do latency compensation.
>
> Pieter, I know the implementation in the freebob driver introduces
> extra buffering in the 1394 stuff, and these values (if known) should
> be added to the port latency assignment.  Otherwise, users have to
> measure it (with jdelay or something) and account for it with the
> systemic latency params.

Many thanks for this patch!

At present it is not possible to assign the internal buffer latencies,
because they are not constant between startups. This is a major flaw in
freebob 1.0, but I decided not to implement a solution because that
would have been too difficult in the 1.0 codebase. The new 2.0 codebase
implements the synchronization mechanism that results in constant
latency, but that code is still under development. I can tell you that
this sync code is the most difficult part of my freebob experience.

Greets & many thanks,

Pieter

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Re: freebob i/o port latency patch

Rui Nuno Capela
In reply to this post by Jesse Chappell
Jesse Chappell wrote:

> While testing the freebob backend I noticed that it wasn't setting the
> port latencies on the interface's ports.  In addition it didn't
> support the -I and -O parameters which let users specify systemic
> extra latency.  The attached patch provides both.  For those who might
> not know, Ardour uses these value in order to do latency compensation.
>
> Pieter, I know the implementation in the freebob driver introduces
> extra buffering in the 1394 stuff, and these values (if known) should
> be added to the port latency assignment.  Otherwise, users have to
> measure it (with jdelay or something) and account for it with the
> systemic latency params.
>
> Also attached (attn Rui) is the patch to make qjackctl let you use these
> params.
>

Applied to CVS HEAD [qjackctl 0.2.20.15]. Thanks Jesse.

You can have a pre-release tarball from here:

    http://www.rncbc.org/jack/qjackctl-0.2.20.15.tar.gz

Enjoy.
--
rncbc aka Rui Nuno Capela
[hidden email]


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