Comments on: Linux / DVB: Playing with command-line utilities

By: Monika Schilling

Monika Schilling — Sat, 28 Mar 2020 16:51:17 +0000

The a.m. “Weird fact:” about dvb-fe-toot is by design. As the man page states:

-m, –femon

Monitors … for a frontend that it is ALREADY BEEING STREAMING via some other application …

By: Alex

Alex — Mon, 24 Sep 2018 21:05:39 +0000

Great post and very informative – thank you! I am experimenting with a TVHeadend server in Brazil, using ISDB-T and this was a massive help. Seems like my main issue is C/N values –

iapps@iapps:/usr/share/dvb/isdb-t$ sudo dvbv5-zap -c dvb_channel.conf -r ‘Globo HD’
using demux ‘dvb0.demux0′
reading channels from file ‘dvb_channel.conf’
service has pid type 05: 500
tuning to 497142857 Hz
video pid 273
dvb_set_pesfilter 273
audio pid 274
dvb_set_pesfilter 274
(0x00) Signal= -63.50dBm postBER= 0
Timeout(0x20) Signal= -20.00dBm postBER= 0
Lock (0x1f) Signal= -20.00dBm C/N= 22.80dB postBER= 0
Layer A: Signal= 79.35% C/N= 45.04%
Lock (0x1f) Signal= -20.00dBm C/N= 23.40dB postBER= 0
Layer A: Signal= 79.35% C/N= 46.05%
DVR interface ‘/dev/dvb/adapter0/dvr0′ can now be opened
Lock (0x1f) Signal= -20.40dBm C/N= 23.40dB postBER= 0
Layer A: Signal= 78.95% C/N= 46.05%

Anyway – probably needs a better antenna alignment. Thanks again!

By: eli

eli — Thu, 27 Jul 2017 19:58:52 +0000

Hello,

Thanks. I haven’t attempted to tune the HD channels. Can’t see the point at the moment, given what is broadcast there.

Eli

By: eldad hadas

eldad hadas — Thu, 27 Jul 2017 19:44:49 +0000

Hey Eli
Great blog, Have you managed to view IDAN+ HD with any DVB-T2 stick?
I got the Geniatech 230c which supposedly has DVB-T2 Capabilities but i only get radio channels]’
i have read that it means that the signal is weak but a Set-top-box with the same antenna gets to see the channels.

Thnx in advnace,
eldadh

By: eli

eli — Fri, 10 Feb 2017 18:09:33 +0000

I know that the channel names come from the stream, but I speculate that there was something wrong with the dongle (such as a short-circuit between a couple of pins) that made it perform horribly bad. So the reception quality was good enough to get some metadata, but not good enough to play video.

And that will remain as a speculation. As I mentioned before, my dongle is dead, and I’m buying another one.

And in case someone reads this correspondence and doesn’t know who I’m talking with: Antti is the Linux kernel maintainer of several media drivers, and the author of the driver of the said dongle. Respect. :)

By: Antti Palosaari

Antti Palosaari — Fri, 10 Feb 2017 17:48:09 +0000

It just update single time statistics when demodulator locks to channel. When demod locks to channel it starts streaming and driver prevents statistic updates (because any i2c access stops streaming due to some stupid hw limitation). First statistic update just after lock is more or less garbage and it will never update any better. I think it is better to disable statistics totally from the driver…
You could use dvbv5-zap -r to tune some channel and then vlc –dvb-budget-mode dvb://dev/dvb/adapter0/dvr0 to view and test for example.
Those channel names are coming from the stream so it is good indicator it is working.

By: eli

eli — Fri, 10 Feb 2017 07:04:38 +0000

Thanks for that input. It’s not every day that I get visited by the chief developer. ;)

The bottom line was that I never managed to get any picture, not using tvheadend (which complained there was no input stream) and not with the command line utilities.

Also, on the few occasions that I got some BER info that seemed meaningful, the figure was around 0.5 (or as it says: 675 * 10^-3 or something).

I’m not an easy quitter, but in this case I gave up. Ultimately, I went for the adventure of trying to fix what I believe were short-circuits on fine-pitch chips, and ended up messing up completely.

So my dongle is dead, and a new HD-901T2 is on its way to me. I suppose it will be easier this time.

By: Antti Palosaari

Antti Palosaari — Fri, 10 Feb 2017 04:46:54 +0000

For that device you cannot trust much for signal statistics (ucb, ber, strength) because device limitation. LME2510C chip has limitation that it stops data streaming after any I2C operation while stream is running. Due to that LME2510C driver blocks all I2C access to demod and tuner when streaming, which means you cannot get statistics from demod or tuner.

Anyhow, your device seems to be working and operational.