Dolby E
Dolby E is a digital audio encoding of Dolby, which is used for transmission and storage of audio material in broadcasting, particularly television broadcasters and post houses. It enables the transmission and storage of up to eight discrete audio channels in standardized data streams according to AES 3id as they are usually designed for the transmission of a stereo signal into two channels of audio in the form of PCM audio. The transmission of Dolby E as part of the AES-3 infrastructure is based on the recommendation SMPTE 337m. Dolby E allows the transmission or storage of up to 8 mono channels (8 × 1.0 ) 4 × 2.0 stereo or surround sound in 5.1 format and simultaneously Stereo 2.0. The number of channels depends on the word length of the recording or transmission system: 6 -channel 16- bit, 8 channels at 20 or 24 bits. Recording or transmission can take place with any bit-transparent medium such as digital video equipment, satellite uplinks, servers or editing systems.
Basis of the encoding is a proprietary and only slightly lossy audio data compression. Dolby E is acoustically transparent and lies in the quality significantly higher than Dolby Digital (AC -3). The data rate is depending on the configuration 1536 kbit / s (with 16 bit word length of the medium) or 1920 kbit / s (at 20 bits), which is about five times as high as in Dolby Digital ( 384 or 448 kbit / s). While methods such as Dolby Digital only survive about three Code-decode cycles, Dolby E allows up to about 13 such cycles and is therefore also suitable for multiple editing of audio material in the course of transmission and post-processing. Before the broadcast with TV stations or during disc mastering DVDs and Blu -ray Discs, Dolby E will be transcoded to Dolby Digital or other methods. As with Dolby Digital ( and limited in DTS) called metadata are parallel to the actual audio signal transfer. This includes information about loudness ( Level Dialogue, dialnorm value ), information on the dynamic range control Dynamic Range Control ( DRC) and for automatic downmixing from 5.1 to stereo (Lo, Ro) or ProLogic II (Lt, Rt ). These tax and descriptive metadata during the production set (metadata editing ) and passed from Dolby E to Dolby Digital. The object of the metadata is the adaptation of reproduction in the home device to the respective playback conditions as well as the loudness control. Dolby E metadata are standardized by SMPTE RDD6.
A significant feature of Dolby E is the fact that the length of the audio frames exactly corresponding to the associated video image. Images are transferred in television technology in the form of a temporal sequence of frames ( engl. frames): For PAL 25 frames per second, ie 40 ms per frame, 29.97 frames per second for NTSC and 33.37 ms. For the period of one frame, for example, 40 ms, Dolby E is the corresponding tone of up to eight channels is encoded and assigned to the video frame. This must in television studios, such as picture cuts or overdubs, done no lossy transcoding of the associated audio signal. It may be associated with a particular video image dedicated audio data as the video data cut or switched. When using Dolby Digital or other methods in the studio of a repeated sequence of coding and decoding of audio signals would be necessary, which would reduce the audio quality through the lossy compression. Although Dolby E is not officially standardized as the norm, it is a de facto standard for the production and transmission of multi-channel sound (Production or distribution Bitstream ) due to its dissemination.