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Poor DVB-T decoding and much errors on Raspberry Pi 4 8GB

Added by Rokas Briedis about 1 month ago

Hello!

I have some problem with DVB-T receiving on Raspberry Pi 4 8GB.

I have two sticks, which can receive DVB-T. One is originally intended for this usage (NotOnlyTV LV5TDLX RTL2832U) and another is intended for SDR (Software Define Radio) usage (RTL2832). Both sticks very good receiving DVB-T on windows computer, both works as SDR`s pretty well. So I decided that which originally for DVB-T connect to Raspberry Pi and setup it, so I can watch TV on raspberry and on my computer (via local network) and to schedued recordings. But there is the problem, with the same antenna, coax cables it does not receive properly. Ok, it receives only one mux. In my location are two muxes, one is 474MHz (2 SD, 2 HD channels, each channel has subtitles and 4 audio channels (Original audio, audio in our native language, native language audio (women), audio for the blinds) and another 658MHz (11 channels, each has one audio channel, no subtitles). So it receives only that in 474MHz. That one in 658MHz it receives, but very poor quality.
I tried receive with VLC, Kaffeine, but no improvement in quality, then I decided to get power USB hub. I read somewhere, that maybe raspberry provides not enough power. But even power USB hub doesn't helped. Only thing which helped, then I changed coax cable from 3m to 0,3m and connected stick via 3m usb extension cable. Only this helped, but only for few days. I mean one day it works perfecly and another not. That, which intended for SDR receives a little better, but quality still poor.
Then I trying to record, data errors says "no, I don't think so" (one hour recording ~300000 errors) and trying to watch it... It is really pain. (In one forum someone complained about he has 60 data errors, and I was: b*tch please, yesterday watch film, which had 1000 times more errors:Dd)
So I know that my antenna works good, my coax cables also good, my stick works well (after those few days I tried on windows and with stick everything good), only problem is raspberry pi or linux. And I don't know where the problem, I think in drivers, but because I`m so green in linux, I don`t n know how to solve it.

Speaking about OS and software. Firstly I tried Ubuntu 20.10, but it seamed very laggy from it self. Then I tried Raspbian OS. It works perfecly (speking about OS), signal quality is a bit better, but still much errors. Then I tried LibreElec. Results was about the same, like with Raspbian. I was always trying to do this with TVHeadEnd and VLC. Doesin`t matter which software I used result was the same. If for no reason it does not receive properly.

I have two teories: maybe raspberry has too much EMS noise or i it`s problem with USB sample rate, although i overclocked it to 2GHz.

Does someone have similar problem? How to solve this problem? Is it problem with linux itself (which I dont believe it is), or raspberry pi?

I also attached screenshots from tvheadend (they are a little bit old, but point is the same
Sorry for my bad english.

BTW I already posted this problem on one facebook group and Raspberry Pi forum. In facebook members said, that i should overclock it and try Raspbian. As you see, I did, and problem still remains

„Opera“ Momentinė nuotrauka_2021-04-12_103349.png (63.6 KB) „Opera“ Momentinė nuotrauka_2021-04-12_103349.png TVHeadEnd errors
Capture.PNG (71.7 KB) Capture.PNG RPI terminal with tunner name
Capture2.PNG (78 KB) Capture2.PNG RPI terminal with tunner name2

Replies (3)

RE: Poor DVB-T decoding and much errors on Raspberry Pi 4 8GB - Added by Rokas Briedis about 1 month ago

Update:
I installed Ubuntu 20.04 on my computer, which has no problem receiving DVB-T on windows.
Results are the same with both stick as with raspberry pi.
Firstly it start to receive at everything seems good. After some time (about 5 min) it start to gliching and after another 5 min it completely unable to watch it.
So the problem is with linux, not Raspberry PI, my computer or adapters (maybe).
Does someone had similar problem with Realtek RTL2832 adapters?

RE: Poor DVB-T decoding and much errors on Raspberry Pi 4 8GB - Added by Hiro Protagonist about 1 month ago

I have two teories: maybe raspberry has too much EMS noise or i it`s problem with USB sample rate, although i overclocked it to 2GHz.

No. A raspberry pi version 1 can handle multiple DVB tuners without problems. A Pi4 can certainly do it. EMS noise is also unlikely to be the problem.

You may need to load firmware into your tuners. See:

https://www.linuxtv.org/wiki/index.php/Firmware

To further diagnose your problem, please post the output from:

dmesg | grep -i dvb

RE: Poor DVB-T decoding and much errors on Raspberry Pi 4 8GB - Added by Rokas Briedis about 1 month ago

Hello,

thats the output of NotOnlyTV LV5TDLX RTL2832U stick:

dmesg | grep -i dvb
[ 1960.744321] usb 1-1.1.4: dvb_usb_v2: found a 'Realtek RTL2832U reference design' in warm state
[ 1960.796059] usb 1-1.1.4: dvb_usb_v2: will pass the complete MPEG2 transport stream to the software demuxer
[ 1960.796086] dvbdev: DVB: registering new adapter (Realtek RTL2832U reference design)
[ 1960.797822] dvbdev: dvb_create_media_entity: media entity 'dvb-demux' registered.
[ 1960.830376] usb 1-1.1.4: DVB: registering adapter 0 frontend 0 (Realtek RTL2832 (DVB-T))...
[ 1960.830399] dvbdev: dvb_create_media_entity: media entity 'Realtek RTL2832 (DVB-T)' registered.
[ 1960.889067] rc rc0: lirc_dev: driver dvb_usb_rtl28xxu registered at minor = 0, raw IR receiver, no transmitter
[ 1960.890054] usb 1-1.1.4: dvb_usb_v2: schedule remote query interval to 200 msecs
[ 1960.898309] usb 1-1.1.4: dvb_usb_v2: 'Realtek RTL2832U reference design' successfully initialized and connected
[ 1960.898775] usbcore: registered new interface driver dvb_usb_rtl28xxu
[ 1961.447042] usb 1-1.1.4: DVB: adapter 0 frontend 0 frequency 0 out of range (174000000..862000000)

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