[PD-dev] yet another video processing external...

[Tom Schouten]

>>>
>
> this would mean you have to extract audio
> of all the videos you have on your hard disk.
> i think we can avoid this.
> ...
>
> that's certainly not feasible to load a 10mn audio track
> in a pd array.

of course, but it is possible for smaller files. up to the user
to not overload the system. plus it is very easy to add this
functionality in a few lines of code, so i don't see who not.
i would certainly have some use for it. a simple "exportaudio <array>"
message would do.

then for audio playback inside the external:

>>>
>>
>> this is certainly possible, but what would happen if the
>> patch bangs at a rate that is slower than the frame rate?
>
> some pieces of silence, and silence
> is part of your art-work ))
> ...
> but i'm interested in "abnormal" playback too.
>

i like the idea of having "granular" playback but i don't like to give 
up the possibility to do normal playback with perfect sync.. there has 
to be a simple way to have both possibilities: chunks & synced chunks.

what about having a "autoplay on/off" message that will switch between 
these
two states. "autoplay off" would play only the chunk of the current 
frame and
stop if no other frame is selected (by a float or bang incoming 
message).
"autopay on" would play the other chunks and output the corresponding 
frames.

if a chunk's playback is finished, a simple test in the dsp function
could determine if a new chunk has to be played and its corresponding 
frame
sent to the outlet.

an "videosync ext/audio" message could dermine which sync state we are 
in:

ext: only react to a "frame x" or bang message, ouput corresponding 
frame and
start playback of the audio chunk.

audio: save the next frame to be output and let the dsp routine descide 
when to
output the frame and start playback of the chunk corresponding to that 
frame (when current audio chunk playback is done)

if avsync = ext and autoplay = on the audio could keep playing without 
outputting
new video frames. if a new frame is requested, the audio playback 
immidiately
switches to the new chunk.

that way you can have playback with silence, without silence, audio 
synced framerate
and external synced framerate.

(another thing: having audio chunk sync would be good for limiting the 
the rate
at which images are decoded. it is easy to overload the system trying 
to decode at
about 500fps. right now i solve this by having a cold inlet that sets
the next frame to play and a hot inlet that outputs this frame when a 
bang is
received. so if you update the frame faster than the maximum sensible 
frame rate (determined by the bang rate), it drops frames... )


tom