saa7134hl NXP Semiconductors, saa7134hl Datasheet - Page 31

• Manufacturer Part Number: saa7134hl
• Description: Pci Audio And Video Broadcast Decoder
• Manufacturer: NXP Semiconductors

Philips Semiconductors
SAA7134HL_4
Product data sheet
6.7.1 TV sound stereo decoding
6.7 TV sound
TV sound is modulated on an internal sound subcarrier, on the upper end of the
TV RF channel, at 4.5 MHz, 5.5 MHz, 6.0 MHz, or 6.5 MHz, depending on the TV system.
The modulation is usually on FM and for system L on AM (see
basically three variants how stereo sound is encoded on analog TV transmission:
Some parameters of the used coding scheme are modulated on an inaudible pilot carrier.
The SAA7134HL incorporates TV sound decoding from the Sound Intermediate
Frequency (SIF) signal. The analog SIF signal is taken from the tuner, digitized and
digitally FM or AM demodulated. The pilot tone is investigated and the signal is properly
stereo decoded. The SAA7134HL supports TV stereo decoding for all NICAM and dual
FM sound systems on-chip. The digital FM demodulation maintains stable phase
accuracy, resulting into improved channel separation, compared to traditional analog
demodulation. BTSC and EIAJ are demodulated to monaural sound, but stereo decoding
can be added externally.
The SAA7134HL incorporates baseband stereo audio ADCs, to capture sound signals
associated with external video sources, e.g. camera, camcorder or VCR.
For concurrent capture of audio and video signals, it is important to maintain
synchronization between the two streams. The spoken word and other sound should
match the displayed picture within a video frame (
special means to lock the audio sampling clock to the video frame frequency (FLC), so
that a certain fix predefined number of audio samples are associated with each video
field. This is especially important for video editing, compression and recording, e.g. time
shift viewing. There is no drift between the audio and video streams, not even for longer
recording times.
TV sound offers an audio bandwidth of less than 15 kHz, that is usually sampled and
digitized with 32 kHz. NICAM as digital sound coding has inherently a 32 kHz sample rate,
locked already on the source side to the video rate. The digital audio stream can be
captured through dedicated DMA into the PCI memory space, or to the output in
I
converted to analog stereo via integrated audio DACs, to feed analog audio over the loop
back cable to the sound card function.
2
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S-format to further peripheral digital sound processing, e.g. virtual surround sound, or
An internal multiplexed carrier for the difference signal L
EIAJ uses FM); this is similar to FM radio stereo
A second independent FM carrier in the RF channel (dual FM), that can carry the
difference signal L
A (second) independent FM/QPSK carrier in the RF channel (NICAM), carrying a
digital audio signal, stereo, or dual language mono
Rev. 04 — 31 March 2006
R, or a second language
PCI audio and video broadcast decoder
1
30
s ‘lip-sync’). The SAA7134HL has
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
R (BTSC uses AM and
Table
SAA7134HL
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