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August 2008 MEETING
Big Screen, Big Sound: Dialnorm, Loudness, Metadata, Proper Monitoring for Multi-Channel 5.1 TV Audio
- Jim Hilson, Dolby Application Engineer for Live Sound and Broadcast
- John Hartwell, Wohler Technologies Chief Technical Officer
- 7:00 PM social hour with refreshments
- 8:00 PM presentation
Program:
For most of US television history, audio has played second fiddle to video, the sound an afterthought to the picture. 25 years ago, two-channel stereo was introduced, the first real audio advance since TV's commercial inception here in 1946. Screens have slowly gotten bigger, although just three years ago, the average diagonal picture size in America was still 27 inches. Lately, picture size has been increasing thanks to aggressive Asian-manufacturer marketing of 16:9 sets in "big box" stores, but the norm for broadcast television remains: "big picture, little speaker". In some cases, "little" doesn't mean "little sound-pressure level" but "cheap and noisy".Now, with the looming deadline next February of the end of NTSC analog TV transmission, along with its limited two-channel audio, we're quickly moving to the universal transmission of 5.1 multi-channel sound, for the first time putting audio at center stage of the viewing experience.
With digital audio's greater dynamic range, broadcasters and cablecasters don't need the extreme compression and expansion ("compansion") that analog forced them to use. NTSC audio's lack of dynamic range, combined with compansion, caused some audio tracks -- e.g., commercials -- to sound louder than the rest of the programming. Ad agencies certainly have always loved this, but viewers have been irritated by it for 60 years. Public outcry has now become organized, with the US Congress wading into the middle of the fray.
ATSC digital means huge dynamic range, about which people may complain more -- or less! -- depending on what the producer and the 'caster do in their audio chains.
Many past analog practices will haunt us as we move forward into digital:
- Locally produced audio, mostly two-channel, needs to match the network audio that has become mostly 5.1, AKA the “We need to keep the 5.1 red light lit” syndrome.
- Producers and advertisers -- programming and spots -- still think they have to compete for viewers' eyes and ears with “We need to be louder than the competition”.
- The current loudness of commercial spots compared to the programs has prompted the US Congress to consider the “Commercial Advertisement Loudness Mitigation Act” [CALM Act, HR 6209] that would require the FCC to enforce commercial loudness limits. But what are those limits in digital, if any?
About our speakers:
Jim Hilson, Dolby Application Engineer for Live Sound and Broadcast www.dolby.com, will tell us about dialnorm (dialog normalization), metadata, and some of the technical requirements for authoring multi-channel audio for broadcasts, cablecasts, and webcasts.John Hartwell, Wohler Technologies Chief Technical Officer www.wohler.com, will explain what loudness really means -- ask six audio-for-video engineers and you'll get seven opinions! -- including the differences between “dialnorm” and “program loudness”, also known as ITU BS-1770/1771, along with monitoring techniques for multi-channel broadcasts.
Welcome:
SMPTEsf welcomes members and friends to attend without charge.Location:
Wohler Technologies31055 Huntwood Avenue
Hayward, CA 94544-7007