[mythtv-users] USB vendor=534d device=2109

[Will Dormann]

On 8/10/20 11:00 AM, Bob wrote:
> On 8/3/20 12:11 PM, Will Dormann wrote:
>> So yeah, it seems not quite ready for prime time.  But given the
>> appropriate efforts spent, it could potentially be viable as a
>> super-cheap HDMI video capture device.
> 
> So, I did a new experiment today and put my cable box in 720P mode. When
> I started to capture the cable box stayed in 720P mode. Previously I had
> the cable box in 1080i and once I started to capture the cable box would
> change to 480p. In this case (720P), the captured output was will
> 1920x1080. Do you think this may be a driver issue or is there an ffmpeg
> option I need to use?


If the cable box itself is switching to 480p, then it's hard to point
the figure at the specific culprit.  I get the impression that something
"unexpected" happens during the capture process.  It's just speculation,
but it could be as simple as the target device "going away" even for
just a moment.  For example, I only saw it happen some of the time, but
I've seen my Fire TV stick go into "pause" mode when I started some form
of capture.  A potential logic for this might be:
- If the Fire stick ever notices an HDMI signal go away, don't blindly
continue playing (because it may not be connected to a TV)
In the case of your cable box, it could be:
- If the box ever notices an HDMI signal go away, revert to the lowest
common denominator for outputting the video signal (because the
connected device might not support the current video properties).

If this is the case, then there could be a couple of potential solutions:
- See if there is a way to disable the 480p fallback in the cable box
settings.  Either through disabling any auto-negotiate options, or
explicitly setting the resolution, if possible.
- Plug the cable box into an intermediate HDMI device, such as an audio
receiver or an HDMI splitter.

Other things to test out may be to see if other capture options, such as
pavucontrol or obs cause the same resolution switch on the box.  If they
behave the same, then the problem could be on the device/driver level.
If not, then there may be some userspace trickery that could avoid this
problem.


-WD