Originally Posted by dr.sound
Then why is it KK that I have never had a QC report over spec?
They are mixing TV but they think they are mixing a feature.
It's TV specs. They are also missing it by 9/10th of a DB not
And don't use the L1 if you want something to sound good. It doesn't.
1. You've been lucky and haven't had program material that generated it...yet. Are you saying that this doesn't exist? Lots of mastering engineers
(including me) would disagree. As stated earlier, the Pohlmann text is illustrative, although it isn't elementary math.
2. TV is more restrictive than theater because they have to comply with FCC and now ATSC specs.
3. .9 dB still trips the meter.
4. When I was a sysop, I spent several hours on CompuServe chatting with Michael Gerzon whose groundbreaking research led to L1 among other Waves plugs. It's definitely an early implementation which has been superseded by later variations, but as with anything, there are ways to use it and not to use it, although I haven't used it lately. Still Gerzon was an excellent mathematician and it is he who first noticed the phenomenon, if I recall correctly. According to him the theoretical max possible clip level was +15, far above .9!!!! Of course you can brickwall limit a couple of dB below threshold, but then you're looking at -8 rather than -6 (assuming -6 is the spec) and you run into critical people who listen with their eyes. If you aren't hitting -6 they think you didn't do it right. Better to have something that will trigger the clip and let you fix the program at just that point.
FWIW, in full disclosure, I like the Waves guys, have written manuals for the company and helped set up sites in Nashville when they were generating IRs for their surround stuff. There's nothing like scooting on a huge Genelec across a hockey rink right after the Zamboni has smoothed the ice.
Oh yeah, we should probably clarify that this topic rears its head in two cases: with SRC and when sending the stream to a DAC. It's all about predicting what will happen inside the DAC, but since we don't listen digitally (yet, still waiting for that plug to otic nerve patch), it's important to know what the reconstructed waveform will be.
Also, here's a reference that shows where a lot of these current topics originated: http://www.itu.int/dms_pubrec/itu-r/...3-I!!PDF-E.pdf
Recommendation ITU-R BS.1770-2 (03/2011)
Algorithms to measure audio programme loudness and true-peak audio level