[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: dynamic compression of comertials

Dear Zlatan,

analog TV "was" a compressed medium by nature, the audio being an FM transmission limited in modulation y the analog radio technology and related problems such as crosstalk with side frequency bands.

The audio, as in radio was limited or compressed and then expanded to compensate for the dynamic loss. You may check for a more scientific data but my believe is that the total range for this medium was around 60 dB.

I do not know the actual limitations in HDTV broadcating, the theoretical dynamic range given by bit depth and electrical noise floor.

I know Dolby Labs "Dolby E" technology was adopted in some HDTV standards. Although this improvement in TV broadcasting gives room to a more cinematographic kind of audio, meaning less limited and soft compressed mixes I think brickwall limiting is still a widely spread practice in audio mixing. Specially in commercials, were loud voicing seems to be still a need.

For cinema trailers the power levels of audio program has been regularized, because in this case exposure to high SPL levels for front rows in the theater could be a health hazard.
Again lacking precission I would say that different mean levels for mixes were approved in different countries, the Scandinavian being the most restrictive.

So the trailers could have tremendous peaks near the pain threshhold but you can not have a sustained level of energy through the entire duration because you must administrate for dynamic not to trespass the maximum mean level allowed.

For TV you can always use your remote control to reduce levels. I suspect some kind of regulation should exist for TV, relating commercial levels to content levels.

Dolby E carries metadata and I think the beginning and end of commercial space could be interpreted by digital receivers user configured to lower the level for those moments.

filmsound.org could be a source for specs on film trailers, Dolby has many papers in its site.

I hope ou find my thoughts useful

Diego Martinez

2011/9/20 Zlatan Ribic <zlatan@xxxxxxxxxxx>
Dear List,
compressed comertials in broadcasting are much louder if compared with "standard" program. Is there any norm limiting this misuse?