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Topic: AC3 volume - What is the story? (Read 9683 times) previous topic - next topic
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AC3 volume - What is the story?

Hi,

All movies with AC3 audio I play in my computer I get a low volume output.

I tried:
- Updating audio drivers/codec
- AC3 Filter
- Media player Classic Home Cinema
- VLC

It still plays at a low volume.
There are so few hardware players that supports AC3, why this audio format is still being used anyway?
Does anybody knows a way to fix this volume issue with AC3?

AC3 volume - What is the story?

Reply #1 –
Quote from: Azevedo on
All movies with AC3 audio I play in my computer I get a low volume output.


Most likely, the gain is actually low in the files.  Increase the gain to compensate.

AC3 volume - What is the story?

Reply #2 –
Quote from: saratoga on
Most likely, the gain is actually low in the files.  Increase the gain to compensate.

Can you show me how to do that please?

AC3 volume - What is the story?

Reply #4 –
There is a theater/movie loudness standard that requires headroom (at least for the dialog...  Loud effects or certain loud parts of music may be "maxed-out" and quite a bit louder than most of the movie).   

Modern MP3s and CDs are generally mastered with zero headroom (normalized/maximized) and highly compressed/limited for that modern constantly-loud sound.

Quote
Does anybody knows a way to fix this volume issue with AC3?
Your best bet is probably to use a player with ReplayGain or just turn-up the volume when you watch a movie.  If these files are not as dynamically compressed as your other music, they may not get as loud.  But, RepayGain will reduce your loud files as well as boost your quiet files to bring everything toward a similar playback level. 

Or, you can open the files in an audio editor to boost the volume.  The downside to that is if you re-save as AC3 (or other lossy format) you'll potentially loose quality.

Quote
There are so few hardware players that supports AC3, why this audio format is still being used anyway?
Every DVD player supports AC3!!!!  It's one of the DVD standards.  About 90% of DVDs have Dolby AC3.  Every NTSC (North America) DVD is required to have either an uncompressed LPCM audio track or an AC3 track.    Since AC3 is compressed, it leaves more room for higher-quality video.  Almost all 5.1 channel DVDs use AC3, although some also have an additional 5.1 DTS track.

Quote
Can you show me how to do that please?
Any editor that supports AC3.    Audacity is FREE (open source) and with the optional FFMPEG import/export library it can import and export AC3.  Or, you can export to any other format of your choice.  Audacity's Amplify effect will scan the file and default to whatever gain is required to normalize (maximize) the volume.


P.S.
I don't know if any video players support ReplyGain.

Also, Audacity will open the audio from an audio/video file, but you'd need a video editor to re-combine the edited audio with the video...  Probably not worth the trouble...

AC3 volume - What is the story?

Reply #5 –
Quote from: Azevedo on
...There are so few hardware players that supports AC3, why this audio format is still being used anyway?....

You probably know it better as "Dolby Digital". 

I produce (small volumes) of DVDs (weddings, mainly) and we always encode and deliver stereo sound as AC3 (and label it as "Dolby Digital 2.0").  Few members of the public have heard of AC3, but Dolby Digital they know.  No-one has ever complained of audio playback compatibility problems.  As DVDdoug says, all DVD players handle AC3 - in fact, I would suggest it is the dominant audio format on DVDs.
Martin - HeadSpin Videography

AC3 volume - What is the story?

Reply #6 –
In MPC-HC i use Normalize. In Options / Audio Swithcer, check Enable built-in audio switcher filter, Normalize, and Regain volume. It helps for me.

Im not the one to explain how this works under the hood, but try it.

AC3 volume - What is the story?

Reply #7 –
Thanks for the answers.

Quote
There is a theater/movie loudness standard that requires headroom (at least for the dialog... Loud effects or certain loud parts of music may be "maxed-out" and quite a bit louder than most of the movie).

Well I don't have the slightest problem with DTS. But dolby Digital is getting me the nerves!


I tried EVERYTHING. Nothing can produce a decent AC3 volume output

Video producers should consider that not everyone live in North America and have a 5.1 system attached to their PC. And yes, there are other hardware players besides "dvd players" and MOST of them (at least in Brazil) won't decode AC-3 audio format.

AC3 volume - What is the story?

Reply #8 –
Quote from: Azevedo on
I tried EVERYTHING. Nothing can produce a decent AC3 volume output


Did you try increasing the gain like described above? 

Quote from: Azevedo on
Video producers should consider that not everyone live in North America and have a 5.1 system attached to their PC. And yes, there are other hardware players besides "dvd players" and MOST of them (at least in Brazil) won't decode AC-3 audio format.


AC-3 is required for DVD video in all regions, so anything that can decode DVD will decode AC3.

AC3 volume - What is the story?

Reply #9 –
So...  AC3 isn't the problem. 

The "problem" is that there IS a loudness standard for moves.  The theater is calibrated so the volume control doesn't have to be re-adjusted when a different movie is shown.  You can also calibrate your home theater system.  I have a Dolby test disc and I think it has volume calibration files on it, but like most people I simply adjust the volume to whatever I feel like at the moment.

On the other hand, there are NO STANDARDS for music except that every producer wants to be louder than everybody else (Loudness War).  If you listen to a classical CD, the volume is probably a lot closer to your movie volume.

I'm not sure if Dolby requires  DVDs with Dolby AC3 to meet the standard, but they certainly encourage or recommend it. 

Somewhere I read that DTS is often 4dB louder than AC3.  I don't know if DTS has their own loudness standard, or that's just something the DVD producer is doing.  (In a commercial movie theater different formats shouldn't have different volumes, but of course movie theaters are not playing DVDs.)

AC3 volume - What is the story?

Reply #10 –
Quote from: saratoga on
AC-3 is required for DVD video in all regions, so anything that can decode DVD will decode AC3.


Ok, let me clear myself...
I'm not referring to retail brand discs like blu-ray or dvd.

I'm referring to players that have an USB port and have an embarked software that can play .mkv, .mp4, ...
Here is when AC-3 won't play.

For PC, using this tweak 'kinda' works
http://www.ac3filter.net/wiki/AC3Filter:Co...sic_Home_Cinema
The output is a bit louder but the sound quality worsens.

IMHO, AC3 should be discontinued...
What a hassle to play files with AC3 codec!

AC3 volume - What is the story?

Reply #11 –
Quote from: Azevedo on
Quote from: saratoga on
AC-3 is required for DVD video in all regions, so anything that can decode DVD will decode AC3.


Ok, let me clear myself...
I'm not referring to retail brand discs like blu-ray or dvd.

I'm referring to players that have an USB port and have an embarked software that can play .mkv, .mp4, ...
Here is when AC-3 won't play.


Well yes, but thats because there is really no reason to support this.  AC3 files are the sound tracks to DVDs.  Having one on a USB stick wouldn't make sense.

Quote from: Azevedo on
The output is a bit louder but the sound quality worsens.


If it sounds worse you're doing something wrong...

Quote from: Azevedo on
IMHO, AC3 should be discontinued...


Its fine for its purpose, a low complexity transform codec that can be used for audio tracks on DVDs. 

AC3 volume - What is the story?

Reply #12 –
Quote
Ok, let me clear myself...
I'm not referring to retail brand discs like blu-ray or dvd.
I assume your movies were copied/pirated from DVD.  I also assume you didn't do it yourself or you would have "ripped" to a different format.

Quote
I'm referring to players that have an USB port and have an embarked software that can play .mkv, .mp4, ...
Here is when AC-3 won't play.
There is PLENTY of software if you want to convert your audio and/or video to another format.    I use a free program called SUPER which can convert to/from almost any audio/video format.    But if you want to try SUPER, BEWARE that it wants to install crapware so you have to be careful about what you click when you install it. 

Quote
IMHO, AC3 should be discontinued...
What a hassle to play files with AC3 codec!
AC3 is the most universal format for 5.1 surround, and almost everybody in the world can play it because almost everybody has a DVD player.    CD, DVD, MP3, and AAC are the MOST UNIVERSAL formats.  These formats are GOOD because almost everybody can play them.  Not everybody has a Blu-Ray player yet, but the standardization means that your Blu-Ray player can play any Blu-Ray disc you buy.     

AC3 volume - What is the story?

Reply #13 –
Quote from: DVDdoug on
The "problem" is that there IS a loudness standard for moves.  The theater is calibrated so the volume control doesn't have to be re-adjusted when a different movie is shown.


There is a standard that says that a -20dB FS pink noise in the file should be played at 83dB SPL in the theater (don't know if it's for a single channel or for all channels played simultaneously). It there really one that says something like "normal dialogs should be mastered at xxdB FS" ?

AC3 volume - What is the story?

Reply #14 –
Quote
It there really one that says something like "normal dialogs should be mastered at xxdB FS" ?
Is far as I know there is no rule that prevents someone from releasing a movie that blasts the viewers with loud dialog.  And, there is enough headroom/loudness available that they certainly can  blast viewers with loud effects or loud or dynamic music.

The calibration standard allows the producers to know (approximately) how loud the sound will be in the theater and it allows the mixing  mastering engineers to do their audio mixing/editing/processing while monitoring at the same calibrated level that the viewers will hear in the theater.  They can use their judgment to make sure the dialog is loud enough to be heard but not so loud that it's annoying.

This is from Bob Katz' K-System paper:
Quote
Over 1000 convention attendees filled the theatre center section. At the end of the demonstration, Tom asked for a show of hands. “How many of you thought the sound was too loud?” About 4 hands were raised. “How many thought it was too soft?” No hands. “How many thought it was just right?” At least 996 audio engineers raised their hands.

This is an incredible testament to the effectiveness of the 85 dB at 0 VU standard originally proposed by Dolby's Ioan Allen in the mid-70's. It’s stood the test of time.


There is a TASA Standard for the maximum loudness of movie trailers.  From what I understand there is no rule that says your trailer can't be quieter.    This is not specifically a dialog  standard but it does say:  "Care should be taken on dialog levels in particular,
such that they do not exceed normal feature film levels...

...If the Leq(

AC3 volume - What is the story?

Reply #15 –
Quote from: saratoga on
Well yes, but thats because there is really no reason to support this.  AC3 files are the sound tracks to DVDs.  Having one on a USB stick wouldn't make sense.

My point exactly. AC3 should be used exclusively on DVD authoring, nowhere else.


Quote from: DVDdoug on
I assume your movies were copied/pirated from DVD. I also assume you didn't do it yourself or you would have "ripped" to a different format.



Well, **** you for wrongful assumptions.
Well then I will assume that Sony, Samsung and LG are pro-piracy by selling players that can play non-bluray/non-dvd files / usb

AC3 volume - What is the story?

Reply #16 –
If you created these files, and you didn't want to use ac3, why did you choose ac3? Just use some other format.

AC3 volume - What is the story?

Reply #17 –
If I get a video file, which I didn't encoded and it is in an AC3 audio format, why you guys are so quick to say that I got a pirated movie? And WHAT IF it was a pirated movie?

I am discussing AC3 format here... not what is right and wrong.

The topic is: "AC3 volume - What is the story?"
and NOT: "Guess if I am a pirate"

AC3 volume - What is the story?

Reply #18 –
Quote from: Azevedo on
The topic is: "AC3 volume - What is the story?"
and NOT: "Guess if I am a pirate"


This was originally brought up in the context of explaining why AC3 gain is different than the gain on CD sourced files.  It was relevant to the topic; you're just overreacting, and quite ridiculously at that.