These standards can be used to transport mono, stereo, 5.1 and 7.1 audio programmes:ĭolby 5.1 uses five channels for normal-range speakers (20 Hz 20,000 Hz) (right front, centre, left front, surround right and surround left) and one channel (20 Hz 120 Hz allotted audio) for the subwoofer driven low-frequency effects.ĭolby 7.1 (non broadcast) uses six channels in the primary program (Independent Substream) for a standard 5.1 surround sound mix and then the remaining 2 channels in an ancillary programme (Dependent Substream) to provide the additional down-mix version.ĭolby E is a video frame-based audio encoding and decoding technology developed by Dolby Laboratories that allows up to 8 channels of audio (mono, stereo, 5.1 or 7.1) for a primary programme (Programme 1) and optional ancillary programs.
There are a number of Dolby digital audio standards that transport audio data within the SMPTE 337M-2000 data burst or AES audio and embedded within the SDI data stream. The daily use of technologies such as Dolby E, Dolby Digital and Dolby Digital Plus in all areas of broadcast television content delivery requires an understanding of the importance of metadata, the transport mechanism as well as the tools to check them.ĭigital Audio is a very broad and sophisticated subject area so here I will only focus on the specific challenges around Dolby E, Dolby Digital and Dolby Digital Plus as part of a SDI transport stream.ĭolby formats in common use in media distribution In the digital audio world where multiple digital audio channels are being delivered at different bit rates, as PCM or in a variety of compression formats, as mono, stereo or surround sound (in many flavours) for use in HDTV, DVD, Cable, Satellite, internet, mobile phone, etc, it can be nearly impossible to spot where things are going wrong let alone work out how to fix them. Likewise if the audio channel has hum or a buzz on it is relatively easy to identify the problem and fix it.
At the pure analogue end of the audio world (which these days is very narrow with much of the audio content being captured digitally) it is quite straight forward to check that an audio channel is present, that it sounds right and has the right levels.
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