[PD] GEM - pix_record problems

oliver oliver at klingt.org
Mon May 30 00:59:22 CEST 2016

hi, dear list !

stumbled across some problems recently when i tried to use pix_record in 
GEM 0.93.3 (on a windows 7 64bit system) that i wanted to report.

message "codeclist"  doesn't ouput anything.
the messages "codec 1" or "codec mjpa" or any other codec message just 
prints the following error:

[pix_record]: unknown codec '

(mind the single quote at the end of the error message -> is that ok ?)
even though i have quicktime and DShow codecs installed.

the same goes for "dialog"   ---> nothing happens ...

doing a recording worked though.

but: the resulting movie file had a BGRA colorspace and was flipped 
vertically. i made a workaround by putting [pix_rgba] and [pix_flip] 
with message "vertical" before [pix_record].

maybe that should be noted in a future helpfile.

the independent "bang" message to manually record frames does not work 
as expected.

i tried it for some sort of stop-motion thingy. the resulting file had 
the number of "banged" frames but the length of the recording (i.e. the 
time between the message "record 1" and "record 0") !
each frame had a different timestamp.

to clean up this mess, i had to use ffmpeg:
ffmpeg -r 25 -i {input} -c:v mjpeg -q:v 0 {output}

the framerate of the recorded movie:

when i recorded in "auto" mode the result was actually quite good 
(according to ffmpeg the codec is "mjpg" after all) but the framerate 
was strange, it changed with the framerate of the gemwin but the 
resulting file had a faster (!) framerate:
gemwin 20 ----> pix_record fps: 25
gemwin 25 ----> pix_record fps: 30

which means the recorded movie played back a little too fast

so here too, to get the real accurate recording framerate, i had to 
correct the fps afterwards with ffmpeg. since this can't be done without 
re-encoding, it's not really a good thing.


other than that: pix_record works great ! ;-)

hope this report is of some help



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