What is the output of
lsof | grep frontend
when VDR is in the "idle" state?
On Sun, Oct 17, 2021 at 10:52:11PM +0300, Marko Mäkelä wrote:
Tue, Oct 12, 2021 at 07:21:10PM +0300, glenvt18 wrote:
Here you can find an updated version of the patch: https://github.com/glenvt18/vdr/commits/vdr-2.4.6
Thank you. I just conducted some tests with my uncalibrated Agilent power supply. The USB cable of such low quality that the Raspberry Pi complained several times about undervoltage.
I measured the following current draw at 5 volts, in ascending order:
81 mA: Raspberry Pi 2B shut down 200 mA: Raspberry Pi 2B powered up, no Ethernet plugged in 240 mA: Ethernet cable plugged in (HDMI cable makes no difference) 320 mA: Ethernet + USB DVB stick plugged in 440 mA: compiling VDR with "make -j4" (all CPU cores busy) 550 mA: VDR playing back a recording 530 mA: recording paused in VDR 510 mA: EPG scan running 600 mA: VDR displaying live DVB-T2
https://github.com/glenvt18/vdr/commit/b368f67d00d0b466ae36028efb9336e81f77d... applied cleanly on the latest VDR source. I changed the PowerdownTimeoutM from 15 to 1 minute to speed up my testing.
The patch only had a minimal impact. After 1 or 2 minutes of the playback of a recording being paused, the power consumption dropped from 530 mA to 500 mA.
I noticed that VDR is consuming about 5% of the CPU power according to "top". Could it not be made more event-based? It might be interesting to check with "powertop" how many wakeups per second there are, and with "perf record" and "perf replay" (or simply "perf top") where the CPU cycles are being spent when the playback of a recording is paused.
The bulk of the the power consumption ought to be caused by the USB DVB stick not being in fully idle state. After all, utilizing all 4 CPU cores during the "make -j4" minutes showed a pretty stable power consumption of 440 mA for several minutes, which is much less than when the VDR process was running.
Here is a summary of the power consumption measured at 5 volts.
1.2 W (240 mA) mostly idle Raspberry Pi 2B (Ethernet plugged in) 1.6 W (320 mA) USB DVB stick plugged in, VDR not running 2.5 W (500 mA) lowest power consumption achieved with VDR 3.0 W (600 mA) VDR displaying live TV
My conclusion is that I will configure udev so that VDR will automatically start up or shut down when the USB stick is plugged in or removed. In that way, the power consumption of the system will only be more than doubled when VDR is actually in use.
I am planning to install the most recent Raspberry Pi and to document the minimal changes on top of that.
Best regards,
Marko
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