“All I wanted to do was to make the sound as accurate as possible — what goes into the microphone comes out the loudspeaker without any nonsense in between.’
– Ray Dolby
On 14 February 2013 at the Holiday Inn, Sandton, a seminar entitled “Delivering Multichannel Audio in a Digital Age’ was offered free to the public by global audio giant Dolby UK, TSL and South African partners Inala Broadcast. Greg Bester was there.
A seminar on multi-channel audio comes at a pertinent point in time for us as South Africans because, as many already know, we are preparing to make the leap into widespread digital broadcast.
Among the many challenges, one in particular is the issue of perceived loudness. One only needs to flip from channel to channel on our current platforms to confirm that there is a massive swing in loudness evident from programme to programme. This, of course, can cause massive annoyances for viewers, particularly those with sleeping babies who have to frantically lunge for the volume control at every commercial break. I, for one, was happy to learn that the seminar would address this.
However, loudness was not the only topic covered as this seminar was set to address the other core challenges when switching over to fully digital broadcast: audio quality, metadata, audio to home delivery and acquisition of sound.
After a warm welcome from the organisers and some breakfast tea, we were quietly ushered into the conference room where four Genelec 1038CFs were set up for left, right, left surround and right surround reproduction, along with a single 8260A for the centre channel. Also present was a large Samsung flat panel display for content demonstrations, a projector and screen.
First up was Dolby’s senior marketing and brand manager, Venkat Venkateshwaran, who gave us an introduction to the seminar and introduced the first speaker, Dolby’s regional director for the Middle East and Africa, Tarif Sayed. After some background information on himself, Mr. Sayed proceeded to give his talk entitled, “Delivering a superior entertainment experience with digital TV.’ He explained why audio is important in broadcast from an emotional and business point of view, bolstered by a quote from the prominent film director, George Lucas
:
“Sound is half the experience.’
Following this, a timeline of Dolby’s accomplishments from 1965 to 2012 was presented with such milestones as noise reduction, 5.1 channel digital audio, surround sound for headphones, HD audio for PCs, 3D digital cinema and fully dimensional cinema sound. Dolby’s partnerships were briefly looked at and then a synopsis of why viewers value audio content, leading into an introduction to digital TV and how it is penetrating world markets. Interestingly, according to Mr. Sayed, 99% of HDTV’s in Europe today support surround sound on the Dolby Digital Plus platform.
Next up was Soundfield Product Manager Pieter Schillebeekx from UK Dolby partners Television Systems Limited (TSL) who gave a presentation of the Soundfield microphone system, the pre-eminent leader in surround sound acoustical capture. Concepts such as acquisition of surround sound for broadcast and the challenges thereof, the Soundfield microphone system’s operation and design, and processing and control were covered. Also delivered was an overview of the DSF-3 remote app, example of events utilising Soundfield, microphone placement, location and music recording and software de-coding.
Following the Soundfield presentation by Peter was Dolby Broadcasts Systems Engineer, Matt Colman. Matt gave the most lengthy of the talks as he was set to cover three comprehensive aspects of digital broadcast namely, Dolby metadata, loudness and delivering multi-channel audio.
First was audio metadata. Audio metadata is the benign set of control messages sent through the broadcast stream to deliver instructions on such parameters as optimal replay configuration and programme information. He explained that by using metadata, a single mono-cast audio stream can be optimised for all end users by broadcasting in Dolby Digital Plus and having the set-top decoder apply the appropriate audio configuration which, depending on your system, can be anything from full 5.1 surround in a home theatre all the way down to the black and white CRT set with mono audio.
Key audio metadata parameters include Downmix which controls stereo/mono downmix; Dynamic Range Control (DRC) which controls dynamic range for stereo/mono and “late night’ outputs; Dialnorm which aligns program loudness; and Channel Configuration which flags channel configuration. DRC and Dialnorm work together to control loudness.
The next part of his presentation included the presentation on loudness, bringing the EBU’s standard R-128 together with Dolby’s Dialnorm and DRC parameters. A variety of concepts were covered, most notably the history of loudness, the EBU R-128 loudness standard and its subsequent rollout in Europe. Basically, to put it how Colman did, abrupt changes in loudness are annoying and equally so is that broadcast loudness is poorly regulated. Not to mention, thus far, standard broadcast practice has been to merely align peak level, which provides very little success in balancing loudness. Accordingly, the EBU instituted the R-128 standard to address the main problems with loudness rooted in the fact that loudness is perceptual.
R-128 outlines a number of specific guidelines for broadcasters and content producers to follow to achieve a favourable balance from programme to programme, as follows:
After a short break, Shillebeekx returned with a short presentation on upmixing to 5.1 and showcased various products such as the UPM-1 stereo to 5.1 converter, including its plugin version. Effective upmixes of stereo material was then demonstrated with impressive results.
Finally, Colman presented his last talk on “Delivering multichannel audio’ which focussed on Dolby E and workflow considerations therein, Dolby E alternatives, trends in broadcast system design and end user delivery in the form of Dolby Digital Plus.
In a nutshell, Dolby E is a “professional audio data-stream designed to carry up to eight channels of audio, metadata, and timecode on stereo PCM systems’. There is one frame of delay for each codec pass and it is carried in a single AES digital pair, boasting a massive data rate reduction compared to PCM audio, making the transport highly efficient in delivery.
The wrap
The Dolby presentation at the Holiday Inn, Sandton, was an onslaught of a wealth of information. Indeed, the seminar lasted the whole day and it would conceivably take many more pages than I am afforded to deliver it in its entirety. However, suffice it to say, everyone came away with something they didn’t know before and new light was definitely shed on concepts of metadata, loudness and the many issues we ourselves are set to tackle in the coming digital future.
By Greg Bester
