A nice feature on DTVs: volume normalization

[David Nebenzahl]

Keep in mind this is just me musing about what would be a nice feature in digital TVs (and converter boxes), not something that actually exists, so far as I know. The thread on how commercials are inevitably louder reminded me of another common problem I've noticed: TV stations have grossly different volume levels. I crank it up for channel 65, then switch to 7 and the damn speaker nearly burns out.

So what would be nice would be a "volume normalization" function. Could work lots of ways: easiest to implement, but most difficult for users, would be a setup option that let you adjust the *relative* volume level for each channel individually (probably just a simple +/- slider control). When you tuned to that channel, it would retrieve this factor and apply it to the current volume setting.

Better for the user, but harder to implement would be an auto-normalization function that would run when you do a scan (or rescan) of channels; it would take a short sample (say 5-10 seconds) of each channel's audio and automatically calculate the normalization factor, then store it. Of course, this would take a lot longer, and it's not guaranteed that the sample time would be representative of that channel's sound level.

This does nothing to alleviate the annoyance of loud commercials; it would simply be a way of "leveling out" the sound level of TV stations without requiring legislation, FCC regulation, etc.

[John Gilmer]

A quick and dirty solution to the problem is "soft limiting" of the audio signal so that the loudest sound tracks are only slight louder than "normal" tracks.

The limiter circuit will detect when a sound source is pushing the limits and insert some loss to minimize the clipping.

It should have a customer preference control to determine whether it should "boost" very quiet tracks or not.

A good sound system will have a good range between the loudest clear reproduction without distortion and the quietest signal that can be heard without distortion. But folks with hearing loss might prefer that the quiet sections be boosted.

Regardless, the "soft limit" will tone down the worse commercials.

I have no idea whether any consumer stuff has these features but the "technology" is old hat.

[larry]

It should get better once the changeover is made. The station engineering staff should have time to adjust their equipment to equalize all their different sources. Then there'll be little change as they switch sources like the studio mike and network feeds. They have their hands full, making all the station changes while trying to simocast in both analog and digital formats.

In the Dallas market, there are substantial sound level differences as I switch around the 40 channels available. The FCC requires monthly station performance tests, to assure all stations provide a consistent, quality signal.

Their advertising rate is based on signal quality and coverage, they must report to the FCC when their power or pattern does not comply with their station license. You pay for ads, you expect a well defined number of possible listeners/ viewers for your money.

-larry / dallas

[dadiOH]

JVC has/had it.

[dadiOH]

You could do all of the above now if you wish and if you are willing to put up with the inconvenience of running the sound from your TV (or any other audio appliance) through your computer as long as that appliance has sound out jacks. Here's how...

1. Get a Winamp 2.x version and install on computer. Winamp bcause it has myriad plug-ins available.
2. Get a DSP (digital signal processor) plug-in that will compress...dsp_compwide is a good one many others are available at Winamp. Comp/wide is configurable via Winamp preferences.
3. In Winamp's preferences, select line input for "input"; select your DSP plug-in under "DSP/effect".
4. Sound out from TV to computer line in, computer line out to your speakers.

You now have even sound.

[greenpjs]

My SA Explorer 8300HD (Time Warner Cable DVR) has it.

[DT]

My Panasonic has it. It claims to "equalize volume levels across all channels and inputs".

[hallerb]

We DVR nearly everything we watch skipping the commercials so the volume doesnt matter.

Have dish satellite TV but looking at getting a dish DTV pal DVR

Why be tied to a network schedule and waste time watching commercials?

[Ed Pawlowski]

The commercial pay for the shows. It would be immoral to skip over them :)

[David Nebenzahl]

On 2/14/2009 8:50 PM DT spake thus:

Yes, but I suspect this is not exactly what I was proposing. What they're no doubt doing is some kind of compression, which tends to equalize volume "on the fly". I'm talking about a more complex system where each channel is adjusted individually.

As there seems to be some confusion here, this has nothing to do with the disparity between the sound levels of commercials vs. regular program material: it has to do with the overall level of each TV station compared to other stations, in which there is wide variation.