Dolby Digital Plus (DD+), also known as E-AC-3, 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, and can carry up to 13.1 channels in a single stream. It has been suggested that High Definition Video be merged into this article or section. ... HD DVD (High Density Digital Versatile Disc or High Definition Digital Video Disc) is a digital optical media format which can hold high definition video or other data. ... Blu-ray discs Blu-ray Disc is a next-generation optical disc format jointly developed by a group of leading consumer electronics and PC companies called the Blu_ray Disc Association (BDA), which succeeds the Blu_ray Disc Founders (BDF). ... Dolby Digital is the marketing name for a series of lossy audio compression technologies by Dolby Laboratories. ...

The algorithm is not directly backwards compatible with AC-3 — existing AC-3 decoders will not be able to decode E-AC-3 streams — but Dolby Digital Plus-capable equipment is required to be able to convert E-AC-3 streams to AC-3 for compatibility with existing Dolby Digital A/V processors. In technology, especially computing, a product is said to be backward compatible (or downward compatible) when it is able to take the place of an older product, by interoperating with other products that were designed for the older product. ...

Technical details

• Coded bitrate: 32 to 6144 kbit/s
• Audio Channels: 13.1
• Sample rate: 32, 44.1, 48, or 96 kHz
• Bit depth: up to 24 bits per channel.

Physical transport

As of 2005, HDMI and IEEE-1394 are planned to support a DD+ stream at its maximum defined bitrate. The High-Definition Multi-media Interface (HDMI) is an industry-supported, uncompressed, all-digital audio/video interface. ... FireWire (also known as i. ...

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. S/PDIF or S/P-DIF, for Sony/Philips Digital Interconnect Format (also IEC 958 type II, part of IEC-60958), is a system for carrying stereo digital audio signals between various devices and stereo components. ...