[PD] Mix two video streams and add DSK
simonzwise at gmail.com
Wed Oct 6 02:49:29 CEST 2010
On 03/10/10 16:37, Jamie Bullock wrote:
> In terms of latency, I get the impression this is a function of the video
> capture method used...
> @Simon, can you tell me which PCI card you are using?
This was a few years ago, I guess the current versions would be PCIe instead
it was a Euresys Picolo Tetra .. 4 chips on the card, each of which switch
between 4 inputs .. there are 4 BNC connectors on the card, plus extension
panels with 4 BNC each for up to 16 BNC total, or make your own panel if you
prefer. A nice features is that each connection has a separate termination
switch, so it is fine to connect some of them in parallel, and since switching
between the source is accessible from inside GEM you can get a very flexible
It wasn't cheap, but I was very happy with it (and the overall system was hugely
cheaper than any digital vision mixer capable of doing what I wanted). The
company does industrial control systems using linux, so all the drivers were
fine .. but actually the standard v4l ones worked well as I didn't need the
extra features accessible via their drivers. I could do 4 simultaneous 640x480
feeds, and the CPU usage sending them directly to the screen was quite
reasonable, allowing several other 1024x768 streams to be played from the disks.
GEM (or rather openGL and the graphics card) scales the image very nicely. With
the good cameras the image was very nice, though with any composite video there
is not much information at better than 320x240 and it was hard to see any
difference going to 640x480, the quality going via DV was better simply because
DV is a cleaner, higher resolution, transfer than composite. The quality
depended on the camera, not the capture. Various high definition capture systems
exist, often very expensive.
Latency was the reason I switched to this system, the performance was set in a
kind of low budget live TV studio, so with a camera on a person speaking the DV
delay was unacceptable, the lip-sync was way too far off between the live actors
voice and the image.
> This project is to port a piece originally done with Max/Jitter to a Pd-based
> system. The main complaints they had were video quality and latency, so those
> are problems we need to solve.
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