Table of Contents
Advertisement
IC DESCRIPTION
A matrix performs the de-matrixing of the A2 stereo, dual and mono signals to obtain the left (L)
and right (R) or language A and B signals.
FM PILOT CARRIER PRESENT DETECTOR
The TV Sound Processor provides FM A2 standard pilot carrier detection.
NICAM DEMODULATION
The NICAM signal is transmitted via DQPSK modulation at a bit rate of 728kBit/s. The NICAM
demodulator performs DQPSK demodulation and feeds the resulting bit stream and clock signal
to the NICAM decoder.
A timing loop controls the sample rate conversion circuitry to lock the sampling rate to the
symbol timing of the NICAM data.
NICAM DECODER
The NICAM decoder performs all decoding functions in accordance with theEBU NICAM 728
specification. After locking to the frame alignment word, the data is de scrambled by applying
the defined pseudo-random binary sequence; the NICAM decoder will then synchronize to the
periodic frame flag bitC0.
The status of the NICAM decoder can be read out from the NICAM status register by the user
(see the control-bus register description). The OSB bit indicates that the decoder has locked to
the NICAM data. The VDSP bit indicates that the decoder has locked to the NICAM data and
that the data is valid sound data. The C4 bit indicates that the sound conveyed by the FM mono
channel is identical to the sound conveyed by the NICAM channel. The error byte contains the
number of sound sample errors, resulting from parity checking, that occurred in the past 128ms
period. The Bit Error Rate (BER) can be calculated using the following equation;
During NICAM mode a switchable J17 de-emphasis is supplied.
-66-
Hide quick links:
Advertisement
Table of Contents
