[mythtv] Re: Audio handling classes [WAS: [PATCH] MythPhone ...]

Jeremiah Morris jm at whpress.com
Thu Jan 27 11:18:38 EST 2005

On 27 Jan 2005, at 7:06 AM, Ed Wildgoose wrote:

> Jeremiah Morris wrote:
>> I'd also love to have dynamic volume control, based on ambient noise. 
>> With pause and commercial skip taken care of, now our biggest TV 
>> annoyance is having to crank the volume when we're making dinner and 
>> running the faucet, boiling water, and so on.
> Basic algorithm is just to look at RMS of some small history of audio 
> samples.  Change volume to bring this up to some preset level.  The 
> trick is to do something sensible when the volume jumps up again (loud 
> explosion or something).  Perhaps it's best to do soft clipping on the 
> loud explosion and then slowly ramp down the volume...? Or perhaps 
> it's better just to immediately cut the volume and build it up slowly 
> again if needed...?

Um, I think you're describing dynamic range control, which is useful 
too but different from what I'm imagining. I want the overall output 
volume to change when the ambient (non-TV) noise level in the room 
changes. The feature would listen to the room, mask out the TV sound 
(this is the tricky part, but it could try to listen only during quiet 
parts of the audio), and send volume-up or volume-down events based on 
how much background noise it hears. If the volume is 60% when it's 
quiet in the room, the feature could adjust it to 75% when our noisy 
dishwasher is running, and bring it back down to 60% when it stops.

- Jer

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