Dolby Digital Plus
From Open Encyclopedia
Dolby Digital Plus, (DD+), was developed specifically for the introduction of HDTV and HD-DVD/Blu-ray discs. The codec supports coded-bitstream rates up to 6.144 Mbit/s, compared to 640 Kbit/s for the original Dolby Digital AC-3.
The algorithm is backwards compatible with AC-3 and can carry up to 13.1 channels in a single stream.
Technical details
- Coded bitrate: 32 to 6144 kbit/s
- Audio Channels: 13.1
- Sample rate: 32, 44.1, 48, or 96 kHz
- Sample depth: up to 24 bits per channel.
- Compatibility: Dolby Digital AC-3 and Dolby Pro Logic.
Physical transport
As of 2005, HDMI and IEEE-1394 are planned to support a DD+ stream at its maximum defined bitrate.
The older and more widespread SPDIF-interface does not have adequate bandwidth for a full Dolby Digital Plus stream (6144 kbit/s). When a DD+ audio track is output to an SPDIF-interface, it must first be downconverted to a lower datarate within SPDIF's capabilities. This downmix is potentially inferior to the DD+ source-bitstream, but still of superior quality to standard AC-3.
