ORF Produces Classical Music in 5.1 Surround Sound
The New Year’s Concert, live from Vienna’s Musikverein concert hall, is Austrian broadcaster ORF’s biggest event of the year and is broadcast to over one billion people worldwide by ORF and their broadcast partners. In the early years, a 5.1-channel mix of the concert had been postproduced for DVD release. The success of this multichannel DVD convinced ORF that the live concert would be the perfect opportunity to launch its 5.1 broadcast services.
The 2003 concert featured music from the Johann Strauss family, as well as compositions from Johannes Brahms and Carl Maria von Weber. Performed by the Vienna Philharmonic Orchestra (Wiener Philharmoniker) and led by the famous Austrian conductor Nikolaus Harnoncourt, the 2003 New Year’s Concert was also Europe’s first live 5.1 broadcast.
ORF chose Dolby® equipment and technologies to implement their multichannel debut.
Recording the Surround Information
When recording audio for surround sound, it is necessary to use a suitable microphone setup that will usually involve more microphones than is common in accepted stereo recording techniques.
The main objective in recording surround information is to record the effects of the hall acoustics, not the direct sound. This can be achieved by placing omnidirectional microphones far enough away from the direct sound source so that they pick up the reverberation of the hall, or by positioning cardioid mics with their null points facing the direct source. If surround mics are placed too far away from the direct source, a sensitive listener may detect a slight delay. It would then be necessary to delay the front channels appropriately. Delaying the front channels is not necessary when directional mics are used as they do not pick up the direct signal.
Setup and Microphone Placement
The microphone layout used for the concert was devised by Florian Camerer of ORF. Twenty spot mics were used to ensure that all instruments in the orchestra were picked up. Three omnidirectional mics arranged in a Decca Tree configuration were used at the front of the stage to give a spatial representation of the orchestra through the front channels. A variation of the Kimio Hamasaki configuration—consisting of two figure-eight mics in the center of the hall and two cardioids pointing toward the rear—was used to pick up the effects of the hall acoustics for the rear channels as well as the audience reaction. No delay was used with this setup.
All of these mics were fed into distribution amplifiers, creating feeds for the FM radio mix, the TV stereo mix, the TV 5.1 mix, and the record-company stereo mix for the CD release.
The Vienna Philharmonic Orchestra performed for audiences in the same venue in the days leading up to the New Year’s Concert. This presented the ideal opportunity to rehearse the live broadcast. In addition to creating the mix, mixing engineer Josef Schütz also developed presets for the metadata that were ultimately transmitted as part of the transmitted audio bitstream. This optimized the soundtrack for replay in different types of home decoders.
A dialnorm value of –25 using “Music Light” on Line mode and “Music Standard” on RF mode was selected. In an unusual move for recording of a classical music concert, some dynamic range control was selected in the metadata. Music Light was chosen to provide more high-level limiting of the signal than low-level boost. This worked well with the particular pieces of music being performed as they contained a large number of high-level passages and very few low-level ones. The effects of these settings were emulated in the OB truck by the Dolby DP570 Multichannel Audio Tool. (Alternately, one could use a software plug-in such as the Dolby Media Emulator to perform the same actions.)
After mixing and emulation of the 5.1 audio and metadata, the media required formatting so that it could be contributed successfully to the ORF broadcast center. ORF chose to use Dolby E in this instance, due to the number of spare embedded AES pairs in the SDI signal over a fiber optic link.
In ORF’s case, the Dolby E was routed and decoded to baseband PCM to prepare the transmission encoder with audio and metadata. The audio encoder was then used to input the ATA board of the Philips platform 310 DVB multiplexer, which in turn fed the ORF DVB transmission over the Astra satellite.
Engineers performed 5.1 monitoring at the concert venue in a special room prepared for the ORF VIPs and at the ORF broadcast center, where the off-air feed was recorded and checked.
The service could then be decoded and enjoyed by ORF satellite viewers with a set-top box that was connected to a compatible 5.1 home cinema system.
It should be noted that to transmit multichannel surround sound, often all the broadcaster has to do is request that multichannel surround be present on the incoming live feed from the content provider, and connect a transmission encoder such as Dolby Digital Plus, which often requires only a software upgrade to existing equipment.