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

IOhannes m zmölnig zmoelnig at iem.at
Fri Dec 28 18:34:01 CET 2012

On 12/28/2012 02:18, Antonio Roberts wrote:
>> i cannot check your example right now, but this can totally be desired
>> behaviour. e.g. if your container supports variable framerates and you
>> record two frames that are 20 seconds appart, you might end up with a 20sec
>> video containing of 2 frames.
>> (afair, you might be able to override the framerate (depending on the
>> backend/container you are using).
> This 20 seconds between frames is what I'm ending up with and I
> believe that it is a bug.

hmm, with "this" is assume you mean that you really get a frame duration 
of 20 seconds (that is, your framerate is 0.05).
if so, then the behaviour is definitely not a bug, as you record two 
frames and that are 20 seconds apart and you also get that.
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).

i understand that this behaviour is not what you want, but the way to 
fix it is:
- 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)
- or ignore the framerate when playing back the file
- or fix the framerate once the file is written (but before you want to 
play it back).

> As far as I understand, pix objects need a
> [gemhead] in order to function. If it is not present or is turned off
> then it shouldn't operate. What I'm finding is that once recording is
> turned on and then afterwards the gemhead is turned off, when it is
> turned back on and a frame captured the time between the two bangs is
> still recorded.

for the sake of completeness:
there's a small chance of a problem with data caching.
[pix_record] will not write new frames if it doesn't receive a 
render-trigger (usually originating from [gemhead]).
but once you turn it on again it might write pixel data that originates 
from before turning on the [gemhead].


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