Re: [tlug] Connecting cameras as webcams

[Christian Horn <chorn@example.com>]

On Mon, Sep 21, 2020 at 02:08:13PM +0100, Darren Cook wrote:
> 
> Christian Horn wrote:
> > Cameras which provide HDMI output might also be interesting for you. 
> > I played with 2 grabbers lately: one sits ontop of a Raspi, the
> > other one gets connected via USB2. For ~3000円 these provide
> > 720p@60Hz capturing, or 1080p at lower frame rates.
> 
> Interesting. I'll look out for that.
> 
> I just read a review of Atomos Ninja V, and it seems cameras output
> better quality video via HDMI than they record to the memory card. So
> that (rather expensive) device allows saving to DNxHD or ProRes, instead
> of H.264/265.

I can imagine that they are limited with the computing power there,
they have to encode live, need to keep an eye on power consumption.

The grabbers I looked at did by themself encode with mpegts or 
x264.  The systems main cpu can then do encoding by itself.  
The interesting parameters for playing with this were
- what is the grabber able to do by itself
- what data rate can then be sent over the bus (CSI to Raspi, USB2
  or USB3)
- which processing can then be done by the main cpu (in case of
  the raspi, the cpu might be limiting)
- and whether latency between the HDMI signal from the original
  device and the video stream which becomes available after
  processing (either on display, or streamed over network)

Christian