[PD] A "multiple problem" with video playing

[Matteo Sisti Sette]

tep wrote:

 > I'm using a few computers to play some synced videos, but i can't get
 > satisfying results using pix_movie.

What is that is unsatisfying?

Is the playback on each computer unsatisfying by itself (in which case I 
cannot be of help, whatever unsatisfying means),
or is the syncronization between computers that is not perfect?

In this second case, "how much" do you lose syncronization, i.e., how 
many frames of difference between any two computers do you accumulate 
per minute?

If you just send a "start" signal to all computer and have them play the 
videos, and expect them to keep synchronized just by the exactness of 
their clock, I think it is impossible (with whatever software or codec) 
to maintain an acceptable synchro (meaning no much more than a couple of 
frames of difference) for more than a few minutes.

I once had to do a synced playback of 3 videos and, if left to drift, 
they could stay apparently synchronized for as long as about 5 minutes.
Indeed I was surprised by GEM's "clock" stability, I didn't expect so 
much (well actually i did, but I had been surprised a few months earlier 
with a similar application).

To guarantee synchro within a given tolerance "forever", I did a patch 
with one "master" and several (in my case 3) "slaves" where the master 
broadcast (via udp) its current time every N seconds (e.g. N=5) and each 
slave compared the received time with its own, and if the difference was 
greater than a threshold (e.g. 2 frames), it forced itself to skip or 
pause the needed amount of frames.

It worked quite well. With a slightly more sofisticated patch you could 
correct the drift in a more gentle way than abruptly pausing or skipping 
a few frames.


I used Windows (not sure whether xp or vista, I think xp) and DV-PAL codec.

By the way, I never used pix_movie's "auto" mode: I turned it off and 
fed the right inlet with a counter incremented by bangs taken from the 
[gemhead]. But i dubt this makes any difference.


Not quite sure this helps...

bye
m.

-- 
Matteo Sisti Sette
matteosistisette at gmail.com
http://www.matteosistisette.com