With the increased demand for multichannel program delivery through broadcast satellite and digital cable networks, Dolby E has recently become more important than ever. But while the technology has been around for some time now, not all engineers fully understand its capabilities or operation.
At Gizmo Post in New York, Airshow Mastering engineer Dave Glasser and I recently mixed a 5.1 and stereo program of the 1992 Montreux Jazz Festival for Rave HD network, as part of an ongoing TV series. Gizmos Brian Mackewich then printed the 6-channel mix in sync with the video via the DP571 Dolby E encoder. Four channels of a Sony HDW-F500 were used to store the mix: the Dolby E stream to a pair (channels 3 and 4 in standard practice) and a PCM stereo mix on the remaining channels.
Dolby E offers the distribution of up to eight channels of PCM audio and Dolby Digital metadata within a standard 2-channel infrastructure. By using a DP571, postproduction houses can easily deliver multichannel content to its clients via stereo digital videotape or a server. The encoded signal is then decoded back to PCM audio using a DP572 Dolby E decoder, typically at the broadcast facility. The decoded audio is then re-encoded into Dolby Digital (AC-3) for transmission.
The DP571 encoder will accept up to four AES-3 channel pairs of PCM audio. That means you can feed the unit a full 5.1 mix along with a stereo track, and it will output a Dolby E stream of encoded audio and metadata via a single AES-3 pair. Conversely, the DP572 accepts a AES-3 Dolby E signal and outputs up to eight channels of PCM audio as AES-3 pairs.
In addition to the DP571 and DP572, we utilized the Dolby DP570 multichannel audio tool. The emulation of downmixing for mono, stereo and Pro Logic decoding through the 570 was very helpful, and having [PC] laptop control made entering metadata much easier, notes Mackewich. As we expected, the 5.1 decode of the Dobly E bitstream sounded exactly like the original signal.
The DP570 can handle up to eight channels of audio (four digital pairs), and can output both a discrete multichannel signal and an emulator signal for various listening modes. Also, it outputs a separate metadata stream, which can later be combined with the surround audio via a Dolby E or Dolby Digital encoder.
For this session, we had Pro Tools feeding the 24-bit/48 kHz digital audio outputs to the DP570, which handled the bass management and downmix/surround emulations. The digital outputs of the DP570 fed the DP571 encoder, which, in turn, fed the Sony HD deck. From the Sony deck, the AES-3 signal was patched into the DP572, allowing us to listen to the decoded mix upon playback.
Dolbys broadcast applications engineer, Ken Hunold, came to Gizmo to help us set up the E network and get us up and running. Dolby offers commissioning and training services on all Dolby products to help studios and broadcast facilities with installation and staff training, Hunold notes. The topics and duration can be arranged on a custom basis; you can contact Dolby Laboratories for rates and scheduling. Dolby staff members are also available to attend and even supervise studio sessions involving Dolby equipment.
The Dolby rep was very helpful in making sure that we had all our bases covered, says Mackewich. What a great resource they were. I would not hesitate to use Dolby E again. It was a joy to work with, and not as intimidating as we initially thought.
With the increased demand for multichannel program delivery through broadcast satellite and digital cable networks, Dolby E has recently become more important than ever. But while the technology has been around for some time now, not all engineers fully understand its capabilities or operation.
For more information, visit Dolby Labs at www.dolby.com.
