| Frequencies(3pm) | User Contributed Perl Documentation | Frequencies(3pm) |
Video::Frequencies - Many, many frequency constants and lists.
use Video::Frequencies;
while (my($name,$list) = each %CHANLIST) {
print "$name\n";
while (my($channel,$freq) = each %$list) {
printf " %-4s %9d\n", $channel, $freq;
}
print "\n";
}
This module exports (yes, exports!) frequency constants as well as hashes with channel => frequency relations for digital and analog video and audio broadcast. Another, shorter way to put it is "worldwide channel/frequency list". All frequencies are given in kHz.
It's a good idea to use "perldoc -m Video::Frequencies" to get an idea on how the various constants and lists look like.
NTSC_AUDIO_CARRIER PAL_AUDIO_CARRIER_I PAL_AUDIO_CARRIER_BGHN PAL_AUDIO_CARRIER_MN PAL_AUDIO_CARRIER_D SEACAM_AUDIO_DKK1L SEACAM_AUDIO_BG NICAM728_PAL_BGH NICAM728_PAL_I
NICAM 728 32-kHz, 14-bit digital stereo audio is transmitted in 1ms frames containing 8 bits frame sync, 5 bits control, 11 bits additional data, and 704 bits audio data. The bit rate is reduced by transmitting only 10 bits plus parity of each 14 bit sample, the largest sample in a frame determines which 10 bits are transmitted. The parity bits for audio samples also specify the scaling factor used for that channel during that frame. The companded audio data is interleaved to reduce the influence of dropouts and the whole frame except for sync bits is scrambled for spectrum shaping. Data is modulated using QPSK, at below following subcarrier freqs
The Channel->Frequency relations are stored in the following hashes. The keys are the Channel names, the values are the corresponding frequency in kHz. For example, "arte" is channel "SE6" in the town in Germany I live in, so, consequently, $PAL_EUROPE{SE6} equals 140250, the frequency I have to tune my receiver.
US broadcast %NTSC_BCAST
US cable %NTSC_CABLE
US HRC %NTSC_HRC
JP broadcast %NTSC_BCAST_JP
JP cable %NTSC_CABLE_JP
Australia %PAL_AUSTRALIA
Europe %PAL_EUROPE
Europe East %PAL_EUROPE_EAST
Italy %PAL_ITALY
Ireland %PAL_IRELAND
Newzealand %PAL_NEWZEALAND
CCIR frequencies %FREQ_CCIR_I_III
%FREQ_CCIR_SL_SH
%FREQ_CCIR_H
OIRT frequencies %FREQ_OIRT_I_III
%FREQ_OIRT_SL_SH
%FREQ_UHF
The hash %CHANLIST contains name => channel-list pairs, e.g. $CHANLIST{"ntsc-bcast"} contains a reference to %NTSC_BCAST.
Nathan Laredo (laredo@broked.net), adapted to perl by Marc Lehmann <schmorp@schmorp.de>
| 2020-11-09 | perl v5.32.0 |