Re: Ardour export question...

[Dale Kazakore Powell <dj_kaza@xxxxxxxxxxx>]

On 20/03/15 01:03, Paul Davis wrote:

On Thu, Mar 19, 2015 at 3:29 AM, Dale Kazakore Powell <dj_kaza@xxxxxxxxxxx> wrote:

But what if you want to listen to audio from a different application connected to Jack while exporting?

That's basically ridiculous.

Why? I don't think it's ridiculous in the slightest! Saying I have done it a lot I guess that should be obvious... My previous install I had PA completely disable so everything always went through Jack (well Jack2 dBus version I believe, if that makes a difference) and sometimes I might want to listen to music while (batch) processing some other audio files. If Jack went into freewheeling then it would prevent my audio I was listening to as soon as Export was started. It doesn't!

 

Surely it should just disconnect from Jack (although this could possible cause routing issues on reconnecting once finished) and run as fast as possible using max CPU cycles.

You're ignoring the idea that export may involve other JACK clients. It may involve, for example, a JACK client functioning as a software synthesizer, or a JACK client function as an "outboard" FX processor. Disconnecting from JACK would be completely wrong in such cases, and special casing the examples where we *could* disconnect from JACK is an absurd amount of extra work given that we are using JACK's ability to drive the process cycle AND share data (even within Ardour itself.

 

Or rather, you're only reading half of my post and ignoring the section where I ask questions about exactly that!!

On 20/03/15 01:03, Fons Adriaensen wrote:

On Thu, Mar 19, 2015 at 03:29:56PM +0700, Dale Kazakore Powell wrote:

But what if you want to listen to audio from a different application
connected to Jack while exporting?

Not possible.

Incorrect!

Surely it should just disconnect from Jack.

That would work only if there are no other Jack clients in the
signal path of the export. In theory it should be possible to
isolate only those that actually are connected somehow to Ardour,
and let the rest run normally, but that is not how it works.

Yeah I realised afterwards I didn't know if it exported with external sources. I still can't see how it can go into freewheeling if it does that, because how does it know these sources are from soft-synths and not real-world instrument which obviously need to be incorporated in realtime?

Actually I know I have personally exported files after normalising
while listening to different music connected through Jack so your
description seems a little strange to me...

That seems impossible. 

Try yourself. Just double-checked here playing music through Audacious set to output directly to Jack and exported a single audio file as mp3 as no interruption of music. Maybe it's because it is only a single audio file, so 100% contained within the Ardour session...

On 19/03/15 23:14, Len Ovens wrote:

When you do this, does the CPU load still go to 100%? Ardour may not be able to switch Jack to freewheeling while another application is connected to one of the HW ports and so exporting would be done at RT speed. This is not a good idea if you are close to the edge with effects/softsynths as freewheeling does not ever have xruns. Also, export speed will be improved if jack can freewheel even in a case where cpu use is quite high in RT.

--
Len Ovens
www.ovenwerks.net

Just double-checked. Exporting a 35min long mix as mp3 took a little over one minute (so clearly nothing like realtime) and Task Manager showed 50% usage and Top 100% usage so it appears to have maxed out a single core. Jack CPU stayed at ~2.2% usage (very conservative settings at the moment.)

On 20/03/15 01:03, Fons Adriaensen wrote:

Does Ardour export with
external sources (eg jack connected soft synths) so only the
internal audio? If the former then it should always be done real
time (maybe the source comes from the real world, not the digital
realm)

If any of the sources required for the export is not a Jack client
or not synced to Ardour or not capable of running in freewheeling
mode, you simply can't expect export to work.

Surely a realtime option would get around this limit, no?? I know Renosie added exactly that option so that external sources or realtime knob-twidling could be included at the time of the export. (Although have to admit I have not tested it, or really touched Renoise since migrating to Linux, so not sure if it works with Jack.)

if the latter then there is no real to involve Jack, or
anything related to the audio interface side of things at all!

No, you could still have processing in other Jack clients which
are connected to Ardour (i.e. external inserts rather than plugins).
A common example would be a mastering processer such as Jamin. 

Ciao,

So why not external effect such as a hardware compressor on your export?



Not trying to argue here, just your claims seem to go against my personal experience so would like to understand why as you guys are obviously much more knowledgeable than myself, especially having the main coder of the software discussed commenting on the thread.


In fact, it seems Ardour ALWAYS disconnects from Jack when not playing!! Keep the Connections tab open start and stop playback. I see the source popping up and disappearing with connections to my output. There is no connection made to Jack when an Export is started! At least when there are no external Jack clients in the mix... This is using US14.04 with the KXStudio repos. Seems to claim Jack uses PortAudio, and the output in Jack is named thusly.

Dale.

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