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Small Technical Encyclopaedia
DVB MPEG-2
DVB is short for Digital Video Broadcasting. DVB-T points to the
transmission method (T = terrestrial). MPEG is short for Moving
Picture Experts Group, a task force drawing up internationally valid
standards for the digital audio and video compression. MPEG-2 was
made the standard in the compression of digital TV signals. MPEG-2
functions in a data rate of up to 100 MBit/s.
Eb/No ratio
The Eb/No ratio is a measure for the signal-to-noise ratio of the digital
signal. This value is not identical to the C/N value know of the
analogue reception technology. In the case of Eb/No values below 5
dB
reception is normally no longer possible.
FEC
FEC is short for Forward Error Correction. The error rate FEC
corresponds to the Viterbi rate.
PID
The PID number (Packet Identification) is an identification number for
video and audio signals in the digital data stream of the DVB-MPEG-2
signals. With the PID number, the receiver can establish a clear
allocation of the video and audio data transmission. The PID-PCR is
the identification number for the synchronisation signal. The PID-PCR
normally is identical to PID-Video. In multilingual programmes, another
language could be assigned to the TV programme via manual audio
PID input. After the PID input, the receiver automatically selects the
audio data identified by the PID from the data stream and assigns
them to the video signal.
Channel Package
For the most part, the channel package contains several TV and radio
channels. Each channel package is fixedly assigned to the transmit
frequency, the polarisation (horizontal or vertical), the symbol rate and
the Viterbi rate or error rate.
Symbol Rate
The symbol rate describes the amount of data transmitted per second.
The symbol rate is measured in MSymbole/s and equal to the amount
of symbols coming in per second.
Video Bit Rate
The video bit rate describes the amount of data of the digitalised
video signal transmitted per second.
Viterbi Rate
The Viterbi rate (Code rate, error rate) characterises the type of error
protection utilised by the programme provider. The DVB standard
determines the following values: 1/2 - 2/3 - 3/4 - 5/6 - 7/8