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

[Will Dormann]

On 7/29/20 7:02 PM, Will Dormann wrote:
> 1. Run pavucontrol (the pulse audio mixer)
> 2. Go to Configuration -> USB Video -> Profile: Multichannel input
> (for me, it was set to "Mono Input" by default, which gave me no sound)
> 3. Go to Input Devices -> USB Video Multichannel -> Port: Multichannel Input
> 
> At least on my system, this was required to get any evidence that there
> was any audio.  If your HDMI input to the device is playing audio
> currently, in pavucontrol, you should see the VU meter fluctuating with
> the received audio levels.   Feel free to celebrate just a bit.


Just to clarify this a bit, as I was having a bit of trouble reproducing
using my own steps.  Despite my capture device having only 4 pins, it
has blue plastic inside of the connector, implying that it's USB 3.0.  I
figured it was just the manufacturer trying to justify charging a couple
bucks more because it's "USB 3.0" because look at the blue.

Perhaps it's just a quirk of how VMware works, but I can say that in my
testing, when the VM is configured to have a USB port that is:
USB 2.0: There is no audio, and the video preview in obs is pretty choppy.
USB 3.1: There is audio, and the video preview in obs is quite less
choppy.  (I blame VMs not having real video acceleration for this)


In my mind, anything with only 4 conductors shouldn't benefit by being
in a USB 3.0+ port as opposed to 2.0.  But I suppose in my case I can't
rule out that the VMware implementation of the virtual USB 2.0 port spec
isn't terribly efficient, and that plugging it into a virtual USB 3.1
port just allows it to perform closer to the maximum USB 2.0 speed.


Anyway, long story short, if you're noticing audio trouble, confirm both:
- The USB audio input is configured for "Multichannel" as opposed to "Mono"
- The device is in a good-enough USB port.


I've confirmed that my VM can go straight from being powered off to
being able to capture with ffmpeg a 1920x1080 video with stereo sound
from a Fire Stick using the steps I've described.  The obs steps are
just to test things out without having to do it blind.   The only odd
behavior I've seen is that sometimes when the capture device is first
plugged into a USB port, the Fire Stick can pause the content being
played (perhaps the same sort of trigger as what caused your cable box
to switch to 480p mode?).  But in a real non-VM machine, I'd expect it
to remain plugged in to things so perhaps that wouldn't be a problem.


-WD