Volume limiter in git...

Hey,

Just checked here:
https://github.com/xbmc/xbmc/tree/31e6e5...69d62d8432
and apx 2 hours ago it seems the 8 year old ticket was closed with the following description.

Added: simple dynamic range compression, a volume amplification slider is now available in the audio and subtitles dialog, which can be used to increase the video volume, a limiter is turned on to prevent clipping.

This limiter is also enabled when a downmix configuration can produce clipping, for example when boost volume on downmix is turned on.

The limiter's hold and release times can be configured through advancedsettings.xml.

Now, originally I think the ticket was opened as a DRC option for DTS etc and from what the description says, I'm a tad confused? Is this DRC for DTS/AC3 bitstreams etc or is this something else?

Can anyone shed any light on this for me, how it will function in the real world, does it amplify quiet sounds to a set db and limit loud sounds to a set db etc..

The description is a tad unclear for me as to how it will actually function and on what types of audio etc?

My main interest in this, is due to the fact that I have a VSX-921 (EU model) which cost apx £500 and has DRC for DTS/AC3 and HD Codecs etc .. However some movies has NO DRC information available and therefore it makes no difference when enabled. This may help to solve this issue if it does indeed add DRC to all content including DTS tracks etc.

Thanks in advance...

I'm hoping we can get a good response on this. I'm very interested in finding out as well.

It's explained in the commit message, that's all it does.

Built-in compressor?! Kick ass!

Is this in the nightly builds? How do you set up the advancedsettings.xml? Would love to test this.

You can configure the limiter hold and release times like this:
Those are the default values, you can use the limiter without adding anything to advancedsettings.xml, just increase volume amplification during playback.
The amount of volume attenuation is shown in the codec info, it's the att value.

Hi bobo,

Thanks for the reply, I've been in and read the commits, however (and this could be down to me being a dumbass) I'm still a tad unclear on how this will function in the real world (for me at least).

I undertstand you've mentioned in the commits that it may not even compile on windows yet, so that will need to be tested first etc so please don't think I'm rushing you or anything...

However, would you be able to confirm, that in essence, this mean, that if I play a DTS 5.1 encoded mkv etc with my audio settings set to DTS/AC3 capable receiver, that this will indeed, allow me to enable a variable "DRC" that will either raise the volume of the quiet parts of the movie (while leaving the louder parts exactly where they are) and/or vica versa?

Therefore, presumably, reducing the large dynamic range that is currently present in some of my movies, when transistioning been explosions and voices etc ...

Also will it be lossy or lossless?

Or is this slightly different from what I Think it is?

As I mentioned earlier, if so that's an Incredible feature, as I currently own a 2011 model £500 Pioneer AVR (VSX-921 EU Edition) That 2011 model AVR doesn't even have a DRC mode that works on all movies.

It has a DRC mode, however it only works for some movies that contain an audio track that includes DRC flags..

As not all my movies have DRC flags, my DRC on my amp is rendered pretty much useless!

As i own the UK version, it also does not have the "Midnight Mode" that is available on the sister "US" version of the AVR.

Also Pioneers ALC is designed to limit the difference in varying tracks (song 1.mp3 / song 2.mp3/ Tv adverts etc and the difference between Movie1.avi and movie2.avi) and not the difference in the tracks contained within a DTS bit stream.

Therefore my £500 "award winning" AVR can't be used at night as it blasts the house down, so currently I am religated to using my TV speakers as they are much quieter...

If this does what I think it does, then you may have stop me from hunting you down and giving you a big wet kiss as this is a HUGE deal for me, as currently, watching movies at night is a complete shambles.

After spending over £1200 on an AVR and 7.1 speakers etc i thought that in the year 2011 a "night mode" would come as standard on even the most basic of models, let alone a decent spec!

Yet, after £1200 total spend, i dont even have the ability to switch to night mode when watching movies in the evening?

Thanks again for the reply and the work you did on coding this into xbmc.

Pat~

night mode (and such raping of the sound) is something you find on the very low end. they have nothing else going for them...

Hey spiff,

It must be the exact opposite with pioneer as the elite range and the higher end 2021 in the VSX range all have midnight mode, where as the 1021 etc don't frustrating to say the least.

I agree that it's a distortion of thr sound, however I have kids and live in an apartment and therefore on an evening (12am-2am) I can't really watch films as the voices are so quiet and gun shots etc are so loud.

Enabling DRC does not resolve this as pioneers DRC works on a flag related encoded system meaning they require the flags to be present to controll the range. As not all movies carry the flags, it means I can't watch a film quietly at night as it just blasts the house down.

For odd occasions like that, or when a new born is asleep next to you in it's Moses basket, I think a night mode is a useful helpful tool, meaning you can still watch the movie and not wake the baby etc..

Headphones are an option but I find I then don't hear all the sounds around me such as baby crying from other room or knocks at the door etc..

while I agree DRC etc damage the enjoyment of the sound somewhat, I think they are very useful and considerate on some occasions.

I think 20mph speed limits damage my enjoyment of driving at times, but I appreciate them outside of my child's nursery

I may return my amp for the 2021 (which is twice the price) as it carries the "night mode" feature but it seems insane to pay almost twice the price (thousands of pounds) for a feature I thought would be standard in this day and age? I find it strange that all AVRs don't at least have the option?

Or if this new limiter does exactly what I need, then I'm very impressed as it will save me fro. Doing so.

However, I'm still a tad unclear on what it actually does? Can anyone explain it at all?

i'll try. in extremely simplified terms.

we have a fixed range [0..20]. where 0 is silence and 20 is max amplitude.
now we have a signal


we want to amplify this by 300% (yes, overkill, just to illustrate). that is multiply the signal by 3. you get

the 30 is outside our data range, so it has to be clipped; the signal becomes

thus the name range compression - the LOUD stuff with a large amplitude is compressed, and is relatively less loud compared to the silent stuff.

dynamic range compression is a "smarter" version of this.