[Ardour-Dev] Non-freewheeling export mode in Ardour 3?

Dragan Noveski perodog at gmx.net
Tue Nov 1 04:37:59 PDT 2011

On 01.11.2011 12:23, Paul Davis wrote:
> On Tue, Nov 1, 2011 at 7:10 AM, Leigh Dyer<lsd at wootangent.net>  wrote:
>> On 1/11/11 9:58 PM, Fons Adriaensen wrote:
>>> But what would be the difference with just recording the signals you
>>> want to export on a new track ? In particular if you could request any
>>> track to use a multichannel file format ? The latter seems to be the
>>> thing to ask for.
>> That might be a nice feature to have anyway, but I don't think it's a good
>> alternative for a non-freewheeling export, for various reasons:
>> * it's more complicated to perform, compared to just running an export with
>> a "non-freewheeling" option set
>> * it needlessly adds the export to the session -- if I have a MIDI only
>> session that's a couple of MB in size, I don't really want to be adding
>> 100MB WAV exports to it
>> * there's no control over export file format (bit depth, sample rate, codec,
>> etc.)
> the problem (as i realized overnight) is that the computational cost
> of export is essentially unbounded and so its impossible to do this
> with JACK in normal mode. sure, one could say something like "well, it
> works on most machines if you use only a single uncompressed export
> format". that's not very satisfactory, and isn't likely to ever be
> reliably true enough to justify the claim in the first place.
> export is fundamentally different to regular streaming via JACK
> because we allow an arbitrary amount of processing to be done with the
> data before it goes to disk *and* in Ardour3, it may actually go to
> disk in multiple formats (multiple files). there's no way to ensure
> that this processing will keep up with realtime JACK. more
> practically, the current code design for export *assumes* that there
> are no realtime constraints on what its doing. adding that would be
> quite hard.
>> Right now, I have to export most of my Ardour sessions by opening JACK
>> Timemachine and recording Ardour's output while it plays back the session.
>> That works fine, of course, but it's a pain, not in the least because I have
>> to make sure I stop the recording when the session has finished.
> sounds like you want a jack-transport enabled recording utility. i
> can't remember if jack_capture can do this, but it would not be hard
> to modify it to do so.


man jack_capture says:

-jt, --jack-transport
               Start program, but do not start recording until jack 
transport has started rolling. When jack transport stops, the recording 
is stopped, and  the  program ends.

i just tried and it obviously does what it should.


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