CBS NETWORK

To recap, distribution of CBS DTV network audio to affiliates uses Dolby E, plus an additional two-channel feed (likely MPEG) via a mezzanine compression system (higher rate than ATSC emission). Affiliate stations must purchase both a Dolby E decoder to get the 5.1 channel program, and also a separate metadata de-embedder.

DOLBY E VIA MEZZANINE

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In an effort to simplify plant timing, routing, and storage issues, CBS network has take a slightly different approach to the audio side of DTV. Dolby E is used to distribute up to eight channels of audio (5.1 plus stereo), and a separate AES pair carries a stereo or LtRt version of the network audio. Metadata is carried separately in the system, and appears in the vertical ancillary space of the HDSDI (SMPTE 292M) signal on the network IRD.

Some CBS affiliates have chosen to install the Linear Acoustic OCTiMAX 5.1 to add protection against wrong or missing metadata. The OCTiMAX 5.1 also gives affiliates the ability to perform straightforward insertion of audio for local content and voiceovers. Because the unit includes upmixing capabilities, the local audio can now fill all of the channels via a simple contact closure from master control thereby seamlessly matching the sound delivered by the network.

KEY POINTS

• Network IRD delivers Dolby E stream
• Baseband audio, video, and metadata signals can be treated as another HD source
• Final emission Dolby Digital (AC-3) encoding is performed at 384-448 kbps
• Adding a Linear Acoustic OCTiMAX 5.1 at the affiliate station can protect audio from incorrect or missing metadata and local content can be selectively upmixed to match network sound sources

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