Video Delay Limitations



  • Hi All

    I have been working with some students playing with time delayed performance. Ideally we'd like to be able to buffer anything up to 10 minutes of video input with the video delay actor, then it be sent to the projector for playback. I have noticed that the video delay will not let me go above 1000 frames (Roughly 30 seconds). Is this a limitation of the software or actor, is there any way to extend this?
    Thanks in advance,


  • This is a hard thing to do, 1000 frames is pretty big. You have to store all the frames somewhere in memory and then red them back as you are collecting more. video delay (even for the pro market) is very hard to do and expensive. To store 10 minutes of video you are going to have to record it in chunks and then play the chunks back. If your frames are low resolution enough you can try using a few of these buffers- you will run out of ram fast though.



  • you can daisy-chain the delays, but look what happens.



  • ...but what i know isadora can only use 2gb of ram for the video delay - look at this tread:

    http://troikatronix.com/troikatronixforum/discussion/1021/livecamera-with-1.5minutes-delay-over-one-hour#Item_6



  • Thank you, very helpful replies. I figured RAM would be a problem at some point. Bodo, thank you for that link, I'll give that a go.

    The other idea we had is to use a Sony HDD Recorder with a camcorder on "timeslip", I know that this will give us the required delay as I've used it on it's own in performance before. I have an ADVC that I can use to send it into Isadora however I imagine latency will be an issue. The students have just this second upped the anti by requesting that we be able to see both live and delayed images super imposed on each other. This project is getting more complicated by the second!


  • Reducing the resolution is really the only way to get 1000 frames. To calculate the required resolution:

    H x W x 4 x FRAMES
    (the x 4 is because there are 4 bytes per frame.)
    So, 
    320 x 240 x 4 x 1000 ~= 300 MB
    400 x 300 x 4 x 1000 ~= 450 MB
    640 x 480 x 4 x 1000 ~= 1.2 GB
    etc.
    Best Wishes,
    Mark


  • Thanks Mark

    I'll give that a go. Sorry for delay in responding. I've been in production for the last fortnight.

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