Articles on: Troubleshooting

Troubleshooting DVB receiving

Detailed guide on troubleshooting DVB reception issues, covering essential aspects such as signal quality, error rates, equipment setup, and interference. Learn practical tips and techniques to diagnose and resolve common problems, ensuring a seamless digital TV viewing experience.

What is BER

BER (Bit Error Rate) is a parameter used to quantify the number of bits that are incorrectly received or decoded in a given transmission. The BER error is an expression of the number of incorrect bits as a ratio or percentage of the total number of bits transmitted.

In DVB systems, the BER error is an important metric for measuring the quality of the received signal. A low BER indicates a good signal quality with fewer errors, while a high BER suggests that the signal quality is poor and more errors are present in the transmitted data. Factors such as noise, interference, signal strength, and transmission distance can all affect the BER.

To improve the BER, DVB systems often employ various error-correcting techniques, such as Forward Error Correction (FEC), which can detect and correct errors in the transmitted data, enhancing the overall quality and reliability of the digital signal.

What is UNC

UNC (Uncorrectable Error) indicates that a received data packet contains errors that cannot be corrected by the error-correction mechanisms employed in the system, such as Forward Error Correction (FEC).

Typically, digital communication systems use FEC to detect and correct errors in transmitted data. However, if the number of errors within a data packet is too high, or if the errors are too severe, the FEC mechanisms may fail to correct them. In such cases, the system reports an UNC error.

UNC errors can result from various factors, including poor signal quality, high noise levels, interference, or problems with the transmission equipment. High levels of UNC errors may lead to degraded video or audio quality, freezing or pixelation in digital TV broadcasts, or even loss of signal.

To minimize UNC errors, it's essential to:

Consider sun interference - Periodic signal degradation, also known as solar outage or sun fade, can occur when the sun aligns directly behind the satellite, causing increased noise levels and temporary signal disruption. This phenomenon typically lasts for a few minutes each day during specific periods of the year
Check the dish alignment and LNB - Connect a signal analyzer directly to the LNB using a short cable
Connect the signal analyzer to the cable on the receiver side. The coaxial cable insulation may be damaged or compromised

All works fine until server reboot

Probably Linux kernel has been updated with autoupdate or manually. Try to reinstall driver.

failed to open frontend: Device or resource busy

Adapter is taken by another process. Maybe Astra started twice.

You may check wich process uses Astra with next command:

lsof | grep adapter0

Example output:

astra 23068 ... /dev/dvb/adapter31/dvr0
astra 23068 ... /dev/dvb/adapter31/frontend0

- astra - process name
- 23068 - process PID
- /dev/dvb/adapter32/... - path to the adapter

failed to open frontend: No such file or directory

The first step is to check whether the DVB adapters are present in the system using the command:

ls /dev/dvb

If the command shows an error message "No such file or directory", the first thing to do is to check if the hardware is available to the system using the command:

lspci | grep Multimedia

If the adapters are properly connected to the PCIe slot, you should see a listing of the PCIe adapters like this:

01:00.0 Multimedia controller: Digital Devices GmbH Cine V7

Try to reinstall the driver. If this doesn't help, please contact the hardware vendor.

Signal is fine, but channels not working

This issue common for adapters by DigitalDevices. Check dmesg output for i2c errors:

dmesg | grep i2c

if you see messages like i2c_write error then turn off MSI (Message Signaled Interrupts) in the driver:

Open file /etc/modprobe.d/ddbridge.conf in any text editor. Find line options ddbridge. After the ddbridge append msi=0 option. For example:

options ddbridge msi=0 fmode=1

Updated on: 24/03/2023

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