Example: Radio and TV broadcasting Network packet

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1 example: radio , tv broadcasting

1.1 mpeg packetized stream

1.1.1 pes packet header
1.1.2 optional pes header


1.2 nicam





example: radio , tv broadcasting
mpeg packetized stream

packetized elementary stream (pes) specification defined mpeg communication protocol (see mpeg-2 standard) allows elementary stream divided packets. elementary stream packetized encapsulating sequential data bytes elementary stream inside pes packet headers.


a typical method of transmitting elementary stream data video or audio encoder first create pes packets elementary stream data , encapsulate these pes packets inside mpeg transport stream (ts) packets or mpeg program stream (ps). ts packets can multiplexed , transmitted using broadcasting techniques, such used in atsc , dvb.


pes packet header

optional pes header

nicam

in order provide mono compatibility , nicam signal transmitted on subcarrier alongside sound carrier. means fm or regular mono sound carrier left alone reception monaural receivers.


a nicam-based stereo-tv infrastructure can transmit stereo tv programme mono compatibility sound @ same time, or can transmit 2 or 3 entirely different sound streams. latter mode used transmit audio in different languages, in similar manner used in-flight movies on international flights. in mode, user can select soundtrack listen when watching content operating sound-select control on receiver.


nicam offers following possibilities. mode auto-selected inclusion of 3-bit type field in data-stream



one digital stereo sound channel.
two different digital mono sound channels.
one digital mono sound channel , 352 kbit/s data channel.
one 704 kbit/s data channel.

the 4 other options implemented @ later date. first 2 of ones listed known in general use however.


nicam packet transmission


the nicam packet (except header) scrambled nine-bit pseudo-random bit-generator before transmission.



the topology of pseudo-random generator yields bitstream repetition period of 511 bits.
the pseudo-random generator s polynomial is: x^9 + x^4 + 1.
the pseudo-random generator initialized with: 111111111.

making nicam bitstream more white noise important because reduces signal patterning on adjacent tv channels.



the nicam header not subject scrambling. necessary aid in locking on nicam data stream , resynchronisation of data stream @ receiver.
at start of each nicam packet pseudo-random bit generator s shift-register reset all-ones.




^ standards (pdf). dvb. retrieved 2014-01-23. 
^ method , apparatus changing codec reproduce video and/or audio data streams encoded different codecs within channel - patent ep1827030






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