[PD] pix_record continues to record, even with rendering turned off

IOhannes m zmölnig zmoelnig at iem.at
Sat Dec 29 20:41:59 CET 2012

On 12/29/2012 16:20, Antonio Roberts wrote:
>> switching off the [gemhead] will not push new frames into your [pix_record],
>> but it will not halt a "local time" (this is never what [gemhead] does).
> Ah, I see now! Although this is expected behaviour, I still think it'd
> be useful to be able to pause recording (at least in this scenario)

bien sur.

>> - either manually force the framerate to a constant value when writing the
>> file (it might well be (haven't checked yet) that you actually cannot force
>> the framerate to a given value, which indeed could be considered a bug)
> I've checked the help file and options and of pix_record and there
> doesn't appear to be any options to set the frame rate. Please correct
> me if I'm wrong!

aye, it's a bit undocumented :-( [*]

like with [pix_video], you can set a number of properties specific to 
the used backend/codec.
when selecting a specific codec, you should get a list of supported 
properties for the selected setting on the info-outlet of [pix_record] 
(that's the 3rd outlet).

e.g. slecting [codec mjpa( gives me available properties "framerate", 
"jpeg_quality" and "jpeg_usefloat".
you can then set these properties using a "set" message:
[set framerate 20(
should give create a film with a fixed framerate of 20fps, whereas
[set jpeg_quality 15(
will give you low quality jpeg compression.

> I did a bit of further investigating and it appears that the framerate
> for the videos created by my patch/pix_record are craziliy high!
> Here's the sample video that I used
> http://dl.dropbox.com/u/350846/test.mov I ran the following command to
> get some information from the file mplayer -vo null -ao null -frames 0
> -identify test.mov
> The important part of that information is that the fps is 1000000.000.
> Something isn't right there...

hmm, i get:
$ qtinfo test.mov | grep rate
     rate 0.608175 [1000000:1644263] not constant

which sounds plausible to me.
might be, that mplayer doesn't report the correct framerate (only the 
numerator, not the denominator)


[*] patches contributing to the docs are welcome.

More information about the Pd-list mailing list