[PD] Mix two video streams and add DSK

Simon Wise 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 
mixer going.

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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