Can someone explain the Normalization and Gain Options please

holygamer

Member
Can you please explain how the Compression, Normalization and Gain Options work. I've got h264 .TS with AC3 files that I'd like to convert to AAC.

Normally I would demux then convert the AC3 to AAC with DB Poweramp then remux. Then I'd use an AAC Gain script with this setting: -r -k -m 0 gain.m4a

Instead I'd like to take my TS AC3 source file and re-encode with VideoRedo to AAC and normalize it to the same volume. What setting should I use to do that.

I tried setting compression to manual and setting the gain level to 0 but that made it a lot louder than my AAC Gain script.

Even just using VideoRedo to convert AC3 to AAC without using an volume settings, the resulting video is out of sync.

I noticed with the Nero Digital AAC Codec that it says you can only convert from Wav to AAC yet VideoRdo and DB Poweramp seem to allow converting from AC3 to AAC? VideoRedo resulting file is out of sync.
 
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Danr

Administrator
Staff member
I think we need to get the sync issues addressed first.

Are you converting AC3 5.1 or 2.0? In either case the output will be 2.0 (at least in Version 4).

Normalization uses a simple peak algorithm. It measures the loudest sample (there are 48000 samples / second), in your output stream, and raises or lowers the volume so that the loudest sample in the output file matches the desired level (e.g. -3 dbFS, 0 dbFS, etc). I would recommend not to go over -3 dbFS.

Automatic Compression uses a smart algorithm that attempts to even out the volumes across the entire video. My favorite example is the 1812 Overture. There are loud parts with the cannon's booming and softer parts. The Compression algorithm will smooth the volumes so they all have roughly the same volume. You can tweak the level up or down with the gain setting.

Manual compression simply raises or lowers the overall volume by xx db.

Both normalization and automatic compression are two pass functions, i.e. we will go through your output edits twice, once to determine the source levels, and then in the 2nd pass to actually change them.
 

holygamer

Member
I'm converting 2 channel AC3. The VideoRedo conversion to AAC is out of sync. However I can demux and remux and it's in sync again but it's annoying that it's not in sync in the first place. There's no delay in the audio of the source.
 

jmc

Active member
@DanR
Quote...
"Automatic Compression uses a smart algorithm that attempts to even out the volumes across the entire video. My favorite example is the 1812 Overture. There are loud parts with the cannon's booming and softer parts. The Compression algorithm will smooth the volumes so they all have roughly the same volume. You can tweak the level up or down with the gain setting."

Heh, gotta try that. I was thinking "Normalization" did it.
Dropping the loud volumes and still being able to hear the lows!

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@Holygamer

I've done a fair number of AC3-MPG to AAC-H264s conversions in VRD
and had no audio sync problems. (with recent modern hardware)
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EDIT...
"Satellite box"... Hmm, never had access to that tech.
I'm all about mpg-tv/movies sources.
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You don't mention what hardware you are using.
Back when my hardware was struggling to do such things
there were audio sync issues.

The Normalization/loudness issues would be trial/error testing for me.

jmc
 
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holygamer

Member
1080i with AC3 recordings copied directly from my Satellite box and cut in VideoRedo. I then tried to save in VideoRedo to AAC without any normalization settings. Played back in MPC-HC and WMP and it's out of sync.
 

Danr

Administrator
Staff member
Is the converted file out of sync when played back in VRD?

I don't have any sync issues on our bug list for the current 681 build. Have you reported this to us?

One more thing, open the source file and click on Tools>Show Program Info. Using the copy button on that screen paste those results here.

Thanks.
 
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