Dolby Pulse Software Encoder

Dolby Digital Plus logoDolby Digital Plus, also known as Enhanced AC-3 (and commonly abbreviated as DD+ or E-AC-3, or EC-3) is a developed by for transport and storage of multi-channel digital audio. It is a successor to (AC-3), also developed by Dolby, and has a number of improvements including support for a wider range of data rates (32 kbit/s to 6144 kbit/s), increased channel count and multi-program support (via substreams), and additional tools (algorithms) for representing compressed data and counteracting artifacts. While Dolby Digital (AC-3) supports up to five full-bandwidth at a maximum bitrate of 640 kbit/s, E-AC-3 supports up to 15 full-bandwidth audio channels at a maximum bitrate of 6.144.The full set of technical specifications for E-AC-3 (and AC-3) are standardized and published in Annex E of A/52:2012, as well as Annex E of TS 102 366 V1.2.1 (2008–08), published by the. Contents.Technical details Specifications Dolby Digital Plus is capable of the following:.

Coded bitrate: 0.032 to 6.144 Mbit/s. Audio channels: 1.0 to 15.1 (i.e.

From mono to 15 full range channels and a low frequency effects channel). Number of audio programs per bitstream: 8. Sample rate: 32, 44.1 or 48 kHzStructure A Dolby Digital Plus service consists of one or more substreams. There are three types of substreams:. Independent substreams, which can contain a single program of up to 5.1 channels.

Dolby Digital Encoder Software

Up to eight dependent substreams may be present in a Dolby Digital Plus stream. The channels present in an independent substream are limited to the traditional 5.1 channels: Left (L), Right (R), Center (C), Left Surround (Ls), and Right Surround (Rs) channels, as well as a Low Frequency Effects (Lfe) channel. Legacy substreams, which contain a single 5.1 program, and which correspond directly to Dolby Digital content. At most a single legacy substream may be present in a DD+ stream.

Dependent substreams, which contain additional channels beyond the traditional 5.1 channels. As dependent substreams have the same structure as independent substreams, each dependent substream may contain up to five full-bandwidth channels and one low-frequency channel; however these channels may be assigned to different speaker placements. Metadata in the substream describes the purpose of each included channel.All DD+ streams must contain at least one independent substream or legacy substream, which contains the first (or only) 5.1 channels of the primary audio program.

Additional independent substreams may be used for secondary audio programs such as foreign language soundtracks, commentary, or descriptions/voiceovers for the visually impaired. Dependent substreams may be provided for programs that have additional soundstage channels beyond 5.1.Within each substream, provision is made for encoding five full-bandwidth channels, one low-frequency channel, and one coupling channel. The coupling channels is used for medium-to-high-frequency information which is common to multiple full-bandwidth channels. Its context is mixed in with the other channels in a fashion prescribed by the metadata, it is not reproduced as a discrete channel by the decoder.Dolby Digital Plus includes comprehensive bitstream metadata for decoder control over output loudness (via dialnorm), downmixing, and reversible dynamic range control (via DRC).Syntax Dolby Digital Plus is nominally a 16-bit-aligned protocol, though very few fields in the syntax respect any byte or word boundaries. As many syntax elements are optional or variable-length, including some whose presence or length is dependent on complex preceding calculations, and there is little redundancy in the syntax, DD+ can be extremely difficult to parse correctly, with syntactically valid but incorrect parsings easily produced by defective encoders.A DD+ stream is a collection of fixed-length syncframe packets, each of which corresponds to either 256, 512, 768, or 1536 consecutive time-domain audio samples. (The 1536-sample case is the most common case, and corresponds to Dolby Digital; the shorter subframe lengths are intended for use in interactive applications like video games where reducing encoder latency is an important concern). Each syncframe is independently decodable, and belongs to a specific substream within the service.

Main article:Both the now-defunct standard, and include Dolby Digital Plus. It is a mandatory component of HD DVD and an optional component of Blu-ray. The maximum number of discrete coded channels is the same for both formats: 7.1. However, HD DVD and Blu-ray impose different technical constraints on the supported audio-codecs.

Rotary Pulse Encoder

Hence, the usage of DD+ differs substantially between HD DVD and Blu-ray Disc.Dolby Digital (AC-3) and Dolby Digital Plus (E-AC-3) bitrate comparisonCodecHD DVDBlu-ray DiscDecodingChannelsBitrateDecodingChannelsBitrateAC-3mandatory1 to 5.1448 kbit/smandatory1 to 5.1640 kbit/sE-AC-3mandatory1 to 7.13.024 Mbit/soptional, available for rear channels only6.1 to 7.11.664 Mbit/sTrueHDmandatoryoptional1 or 23 to 818.0 Mbit/s18.0 Mbit/soptional1 to 818.0 Mbit/sOn HD DVD, DD+ is designated a mandatory audio codec. An HD DVD movie may use DD+ as the primary (or only) audio track.

An HD DVD player is required to support DD+ audio by decoding and outputting it to the player's output jacks. As stored on disc, the DD+ bitstream can carry for any number of audio channels up to the maximum allowed, at any bitrate up to 3.0 Mbit/s.On Blu-ray Disc, DD+ is an optional codec, and is deployed as an extension to a 'core' AC-3 5.1 audiotrack. The AC-3 core is encoded at 640 kbit/s, carries 5 primary channels (and 1 LFE), and is independently playable as a movie audio track by any Blu-ray Disc player. The DD+ extension bitstream is used on players that support it by replacing the rear channels in the 5.1 setup with higher fidelity versions, along with providing a possible channel extension to 6.1 or 7.1. The complete audio track is allowed a combined bitrate of 1.7 Mbit/s: 640 kbit/s for the AC-3 5.1 core, and 1 Mbit/s for the DD+ extension.

During playback, both the core and extension bitstreams contribute to the final audio-output, according to rules embedded in the bitstream metadata. Media players and downmixing Generally, a Dolby Digital Plus bitstream can only be transported over an HDMI 1.3 or greater link. Older receivers support earlier versions of HDMI, or only have support for the system for digital audio, or analog inputs.For non-HDMI 1.3 links, the player can decode the audio and then transmit it via a variety of different methods.

Earlier versions of HDMI, such as HDMI 1.1, support, where the player decodes the audio and transmits it losslessly as PCM over HDMI to the receiver. Some receivers and players support analog surround sound, and the player can decode the audio, and transmit it to the receiver as analog audio.Most receivers and players support S/PDIF.

This lower bandwidth digital connection is not capable of transmitting lossless PCM audio with more than two channels, but a player can transmit a S/PDIF compatible audio stream to the receiver in one of the following ways:. players can take advantage of the legacy 5.1 AC-3 bitstream embedded in the E-AC-3 bitstream, transmitting just the AC-3 bitstream with no modifications. Players supporting the standard can transcode the decoded audio into another format. Depending upon the method and options available to the player, this can be done with relatively little quality loss. Dolby's reference decoder, available to all licensees, exploits the common heritage between AC-3 and E-AC-3 by performing the operation in the frequency domain. Hybrid re-compression avoids unnecessary end-to-end decompression and subsequent recompression (E-AC-3 → LPCM → AC-3). In addition to AC-3, some HD DVD players transcode audio compatible with S/PDIF into 1.5 Mbit/s.

While S/PDIF can carry Dolby Digital Plus at lower bitrates, the HD DVD standard specifies a bitrate for DD+ which is too high for a S/PDIF interface to transmit.Should the player need to decode the audio for a non-HDMI 1.3 receiver, the results should be predictable. The DD+ specification explicitly defines modes and mechanics, so any source soundfield (up to 14.1) can be reproduced predictably for any listening environment (down to a single channel).See also.References.