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What lightest possible format for multi-screen playback
Hi all,
I’m working on a video installation with four individual videos on four separate old tv screens running from a single computer through QLab. Currently the files seem to be too heavy, although we’re only running tests with videos less than a minute in length. Does anyone know what format/codec etc we should choose when exporting so that the resulting files are as little demanding as possible for the computer running them through QLab? The image definition doesn’t have to be too high as the videos will played on old crt tv screens.
Any help would be much appreciated!!
Thanks,
Kari
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2 Replies
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Just looked at the specs for QLab. Your issue is probably not your codec but the CRTs. The direct answer to your question, “what is lightest,” is MP4 h.264. For standard definition, a bitrate of 10Mbps would be high-quality and should not be an issue for any modern system.
Your problem is probably a signal issue. You are sending the wrong signal to the CRTs. Most CRTs (in the US) can only handle a true NTSC signal, even if it has a digital input (rare). Your starting file should be 720×486 (non-square) interlaced at 29.97fps, though it may be hard to make an interlaced MP4. Possible in theory but not in practice. More common for interlaced playback would be standard MPEG.
At some point you are doing A/D conversion. You can start with anything your signal convertor can understand but you have to end up with 720x486i29.97 or the CRT cannpt display. That’s assuming this is a television. If it is a computer monitor, well, too complicated to get into here.
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Thank you Tod for your long answer and sorry for replying so late! We were sweating blood to make the deadline..
For the sake of completeness, here are the solutions we found:
- We ditched Qlab, too expensive for our mini budget, and found a better solution for synchronizing the 4 videos playing on the separate screens: 4x raspberry pi devices, one for each video/screen, loops synched and played with the open source application MP4Museum
- The raspberry pi’s have an analog video output for CRT TV screens, and an HDMI or TV out
- As per MP4Museum website https://mp4museum.org/video-howto/ we exported the videos in ProRes before converting them to MP4 with the open source tool Handbrake
- In case anyone is interested in knowing how we edited the 4 separate videos so they would synch, we used the tiles in DaVinci Resolve (“video collage” “create tile”).
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