How MTS Audio Channels Are Used
The second audio program (SAP) also is part of the standard, providing another language, a video description service like DVS, or a completely separate service like a campus radio station or weatheradio.
A third PRO (professional) channel is provided for internal use by the station, and may handle audio or data. The PRO channel is normally used with electronic news gathering during news broadcasts to talk to the remote location (such as a reporter on-location), which can then talk back through the remote link to the TV station.
- Specialized receivers for the PRO channel are generally only sold to broadcast professionals.
- NICAM has a similar pro-channel feature that has only been implemented in the UK (http://stoneship.org.uk/~steve/nicam.html#SPARE).
MTS signals are indicated to the television receiver by adding a 15.734 kHz pilot tone to the signal. The MTS pilot is locked or derived from the horizontal sync signal used to lock the video display. Variations in phase or frequency of the horizontal sync are therefore transferred to the audio. UHF transmitters in use in 1984 generally had significant phase errors introduced in this signal making the transmission of stereo audio on UHF stations of that time nearly impossible. Later refinements in UHF transmitters minimized these effects and allowed stereo transmission for those stations.
Read more about this topic: Multichannel Television Sound
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