DSLR Video - how does it work? (techincal)

Started Oct 20, 2009 | Discussions thread
bob elkind Veteran Member • Posts: 5,819
a minor nit

Thom Hogan wrote:

Can't speak for Canon, but I'm pretty sure that's not exactly how Nikon does it. D-Movie came as a freebie from the Live View stream, which also goes to the HDMI output port.

After playing with a few Nikon bodies, it's a good bet there's a conversion device between the LiveView stream and the camera's rear LCD, for timing and scaling of the video to feed either the LCD or the HDMI port (but not both concurrently).

I wouldn't be surprised to find that whatever part drives the data on that [HDMI] port is what is doing the conversion. This brings up questions about where the Picture Controls are being applied in real time: it appears to me that if I crank up Sharpening, EXPEED has to be doing that, but the HDMI conversion comes downstream of that, so you can get ugly artifacts by cranking certain controls up too much.

I think all M-JPEG video conversion happens upstream of the LCD/HDMI formatting. The video stream is 24FPS, and the LCD (and the HDMI output) is driven at or around 60FPS refresh rate... so some re-timing (as well as addition of overlay screens) is added to the processed video before the resulting display is output to either the LCD or the HDMI port.

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Bob Elkind
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