[mythtv-users] Configuring USB3 HDMI capture device non-HDCP source

[Devin Heitmueller]

> I believe the device can output in a few different formats, I'm going to
> mess with that a bit today. For the analog capture devices, I can't set the
> recording profile to 1080p, only like 700x580 or something so the device is
> downscaling. I'll see if I can use v4l2-cfg to set the frame rate. When I do
> a non-raw capture, it understands that the frame rate is 30 or 60 (depending
> on what I set in steamer) and VLC reports that and plays it back properly.
>
> I can also try twiddling with the code to see if I can get some additional
> parameters passed to the device, do you know where this code would be?

It tends to be heavily dependent on the device.  Most webcams let you
adjust the frame rate and resolution because the net effect is how it
configures the onboard image sensor.  However with a device that
consumes digital video from an HDMI source, there are more limitations
on how much control the receiver can exercise in terms of resolutions
and framerates.  If the device supports frame decimation and/or
scaling then it can be pretty flexible.  However if it's more of a
"dumb" device, then it just takes whatever comes back from the HDMI
receiver chip and pushes it over the USB bus.

You might want to load the device up under Windows and see what
options are offered to you, as that might provide some guidance as to
what the hardware is actually capable of.

Regarding 1080p vs 700x580, my guess is MythTV has some hard-coded
resolutions (based on typical NTSC/PAL use cases) and the actual
commands to set the resolution in the hardware are completely ignored.
You would probably have to save a few frames of actual video from the
driver and see what their effective resolution is, as opposed what
MythTV is supposedly telling the device to operate at.

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com