Req Option to allow "Volume Amplification" for Dolby Digital (explanation inside)
#1
Rainbow 
Hey there, Blush

although there is not much talk about it, the simple "Volume Amplification" (DRC) feature in KODI works really great to reduce the insane volume difference between dialogues and explosions in most movie HD audio soundtracks. (Even for big home cinema setups, the difference is just too big in many cases.)

Over time, i got to love the following setup:


Hardware is an AVR with larger 5.1 Surround cinema speakers. KODI is running on a i5 4-core Intel NUC.


KODI Setup:

Number of channels: 2.0 (Which does NOT mean you only got 2.0 audio for Multichannel audio. You still get your 5.1!)

Resample Quality: High (It may not be relevant for transcoding (KODI Team members maybe can answer that?) - but since the hardware can handle it, i preffered High.)

_CHECK_ Enable passthrough
_CHECK_ Dolby Digital (AC3) capable receiver
_CHECK_ - Enable Dolby Digital transcoding (So every other (HD) audio format gets transcoded back to simple and nice 5.1 Dolby Digital after Volume Amplification (DRC) has been done)
_ DISABLED_ Dolby Digital Plus (E-AC3) capable receiver
_ DISABLED_ DTS capable receiver
_ DISABLED_ TrueHD capable receiver
_ DISABLED_ DTS-HD capable receiver

KODI Audio Main Volume: -10.2db
KODI Audio Volume Amplification: +10db

Result:

Almost every movie audio gets decoded, Volume Amplification +10db is applied, Main Volume -10.2db gets the volume back to a normal state and with transcoding back to simple Dolby Digital AC3 you wind up with a nice DD 5.1 Signal without insane volume differences between dialouges and explosions.

It works very very well and gets the job done for almost all situations!
Only if the source audio is DD AC3, it doesn't work, because this audio gets passed through untouched and therefore no Volume Amplification (DRC) is applied.


Feature request would be an (really optional) option, that allows you to force decoding and transcoding even if the source audio i already simple DD 5.1 AC3.


So this could be done:

- The new option "- Allow/Force Dolby Digital transcoding even if source is already simple Dolby Digital AC3" is _CHECKED_
- Movie audio is "old" simple Dolby Digital AC3, but still gets decoded
- Volume Amplification is applied
- Transcoding back to Dolby Digital AC3
- Larger volume differences between dialouges and explosions are reduced for simple DD AC3, which was not possible before in that way




Thanks for reading!
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#2
Any passthrough means xbmc/kodi doesn't touch the audio at all.

so

KODI Audio Main Volume: -10.2db
KODI Audio Volume Amplification: +10db

^^ isnt used at all while on passthrough its actually disabled since its now the job for your AVR to handle this.

What you are asking is for this to change tbh idk but I doubt it. but this is just my thoughts.
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#3
(2014-12-16, 22:29)uNiversal Wrote: Any passthrough means xbmc/kodi doesn't touch the audio at all.

KODI Audio Main Volume: -10.2db
KODI Audio Volume Amplification: +10db

^^ isnt used at all while on passthrough its actually disabled since its now the job for your AVR to handle this.

Thanks for your reply!

Yes. That's what i said? ^^
Only the simplest AC3 DD 5.1 source audio can't profit from the setting because KODI does not see the need to decode it and encode it back to AC3 DD 5.1 again like it does with all other multichannel audio tracks. (Since my settings say the AVR is AC3 capable, it doesn't allow decode+encoding back to AC3 again. One solution would be to disable AC3 and output Multichannel LPCM via HDMI, but not all AVR support LPCM.

Result at this state:

Works:
- DolbyDigital TrueHD - [decode] - VolumeAmplification (DRC) - [encode] - AC3 DolbyDigital 5.1
- DTS - [decode] - VolumeAmplification (DRC) - [encode] - AC3 DolbyDigital 5.1
- DTS-HD - [decode] - VolumeAmplification (DRC) - [encode] - AC3 DolbyDigital 5.1

Does not work:
- AC3 DolbyDigital 5.1 - [decode] - VolumeAmplification (DRC) - [encode] - AC3 DolbyDigital 5.1


With the mentioned settings you can use -10.2db combined with +10db VA for a very good Dynamic Range Compression for almost all movies that exist, except for movies which already have basic AC3 DD 5.1 audio. If your AVR supports LPCM HDMI you're lucky and can use that as final output, but if you want AC3 DD 5.1 as final output, you can only use DRC for everything except for movies which already have simple AC3 DD 5.1.


At the end it's about KODI not knowing why it should allow decoding+encoding something like this:
AC3 DD 5.1 - [decode] - VolumeAmplification(DRC) - [encode] - AC3 DD 5.1,
because you selected the AVR is capable of AC3 in the settings.


The possibility that one like would like to have VolumeAmplification(DRC) in the middle of the process has not been considered in the past.

I think Volume Amplification is barely talked about at all, although it's so useful for home setups.
Most users don't even know what it's about, not to mention they couldn't know how to set it up for DRC (-10.2db & +10db) without the extensive testing some more experienced users did. (There has been an old thread with one user who ended up at -12db & +12db, so almost the same result i came to trying it out myself over a long time.)
I can assure it works better than most of DRC-mechanisms which are integrated in many AVR.


Thanks again, have a good night
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#4
Isn't it easier to set it up in your reciever ?
This way xbmc can passthrough the audio without any post processing.
Some receivers have dynamic volume control (could be named different on your system)
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#5
(2014-12-17, 06:59)TRaSH Wrote: Isn't it easier to set it up in your reciever ?
This way xbmc can passthrough the audio without any post processing.
Some receivers have dynamic volume control (could be named different on your system)

Hey!

The DRC in most AVR is bad and often even useless. Many AVR have licenced some DRC-technology or even have their own, but mostly they are not good and effective. (I tested many not so cheap AVR)


Besides that, i've written down everything i could in the last two posts. Smile


Greets
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#6
Why don't you simply send everything to the AVR as PCM?
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#7
Hey jjd-uk,

thanks for checking in!

The AVR has no HDMI ports and therefore doesn't support Multichannel LPCM. 2 Channel PCM is max (SPDIF Optical/Coax). Since SPDIF Optical Out is still very common in home cinemas, i think it's not ONLY me that would benefit from it.

If it had HDMI i would have used exactly this workaround (send everything via HDMI Multichannel LPCM) as mentioned in my second post.


I know it may not happen, but allow me to ask:

In theory, technically it should be no problem for KODI to do:
- AC3 DolbyDigital 5.1 [decode] VolumeAmplification (DRC) -10db +10.2db [encode] - AC3 DolbyDigital 5.1
is that correct?

Thanks again!
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#8
Ah ok, it wasn't that clear to me the AVR didn't have HDMI.

I think it's unlikely like this will be added by the Audio devs, however a Audio DSP system is under review which will utilise add-ons for stuff like DRC which may allow you to achieve what you're after at some point in the future.
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#9
Side note (should not be important for the topic):

Although the AVR has no HDMI, my KODI-device outputs audio via HDMI.
KODI AUDIO setting: HDMI, 2 channels, Enable passthrough, Enable DD, Enable DD Transcoding, _Disabled_ all other formats below that (AC3-E, DTS, DTS-HD, DDTrueHD)

Reason:
I got the NUC connected to a good (1.4a) HDMI 4x2 matrix which has a COAX SPDIF port. This is where i catch the DD AC3 from the HDMI signal and put it right into my AVR.
Works well! Smile
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#10
Allright, thank you.

Then i think i'll look for an old used AVR (the exact successor model to mine) which has HDMI so i can use it for Multichannel LPCM. (I won't use the AVRs HDMI for anything else then audio, the rest of the setup will stay as it is)
May be the best idea to get a quick solution.

Can i do something to make this request last, so the devs may read it while reviewing the Audio system? I know it still most likely won't happen. Thats okay. Smile
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#11
OK - I was pointed to this thread from another. When I ripped all my DVDs I used Handbrake and the sound I left as auto-passthrough, so they have (mostly) been left as AC3. So it looks like I would benefit from a "force transcoding" option.

However, as this isn't likely, I will probably ffmpeg the whole library - any suggestions as to best format to move them all to?
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#12
I have to ask again: Does your AVR has HDMI ports?
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#13
So as you mentioned in the other thread - there are no HDMI ports on your AVR.

Without a force transcoding option in KODI to allow transcoding on AC3 you only have the option to transcode the AC3 track in your files - which really isn't an option in my opinion. (if there are many files)
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#14
Made some tests just out of interest...

If you are willing to transcode your AC3-tracks in your files (which would be no option for myself, but maybe you want to do it):

Using ffmpeg to transcode AC3 to EAC3 (Dolby Digital Plus) would (one) solution. The audio tracks would stay almost the same size but KODI is willing to decode them because they are not simple AC3 anymore, but EAC3.

(just a snippet, not complete command for ffmpeg)

-c:a eac3 -b:a 640k

(As bitrate i would at least choose 640k (which is max. for simple AC3). EAC3 can go higher, but 640k may be enough for you (decide yourself).)



If you don't care about some extra MB in your files, you could create a EAC3 audio track and add it to the original file as an additional audio track, so you don't lose the original AC3 data.
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#15
thanks - I may give that a shot - or just re-rip those movies that have massive sound differences - some of them I think I applied DRC in Handbrake on the rip, so I'll do it on a case by case basis
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