Re: Making VDR run under Systemd

Hi all, hi Martin!

Mon, Sep 13, 2021 at 08:51:05PM +0200, Martin Wache wrote:
>Yes good times! :-)

I think that softdevice (without HD in the name) was quite an 
achievement for the hardware that was available about 20 years ago.

Today, I made a little progress on this. First, I was thinking to set up 
an unused IBM Thinkpad X60 for VDR. In the end, I found out that 
softhddevice depends on a number of X11 libraries.

I also found some forum posts that suggested that it is not expected to 
work with Wayland. If I understood correctly, Wayland helps reduce the 
CPU overhead, as long as there is some GPU support for compositing RGBA 
buffers, and it could simplify the rendering path.

In the end, I decided that one 32-bit CPU core (2 with hyperthreading) 
and a 1024×768 screen panel would likely not be a good match for HDTV.

So, back to the plan with the Raspberry Pi 2B. One problem that I wanted 
to solve is the power consumption of the DVB-T dongle when it is not in 
use. I found https://github.com/mvp/uhubctl which can switch off power 
on individual USB ports. I wrote a VDR shutdown script that does the 
following:

sudo service lircd stop
uhubctl -p ... -a off
sudo service vdr stop

I did not refine the uhubctl invocation yet. The physical port could 
vary.

An easy way to start up VDR could be a udev rule that would start up the 
lircd and vdr services when the USB DVB stick is plugged in. Obviously, 
if we power off the port during VDR shutdown, the adapter would have to 
be plugged into a different port.

A simpler option for the occasional use of VDR might be to simply write 
udev rules that will start up lircd and vdr when the DVB adapter is 
plugged in, and shut down the services when the adapter is removed.  
That would be too risky if recording timers are being used.

I am not yet sure whether powering off the USB port makes any 
difference, because the plastic case of the DVB stick feels slightly 
warm to the touch even when the port is supposedly powered off. It might 
be that some internal heat produced by the Rasberry is being dissipated 
via the USB port. The metal frame of the USB jacks feels a bit warm too.

I think that I must measure the input power of the Raspberry Pi as well 
as the voltage on the USB port when it is supposedly powered off.

	Marko

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