Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > General > Audio encoding

Reply
 
Thread Tools Search this Thread Display Modes
Old 4th February 2007, 17:08   #1  |  Link
ddawes
Registered User
 
Join Date: May 2006
Posts: 8
lowpass filter when encoding ac3

Morning,
Downmixing 6ch wav to 5.1 ac3 using BeSweet. Is there a CLI switch that I may use to control whatever the preset freq is for the lowpass filter to LFE? I would like to remove bass from all other channels and send directly to LFE. I can set that from the BeSweet GUI "Azid 1" settings page, correct, by checking "LFE to LFE output" box? Am I not seeing an option to adjust that freq, somewhere? Also, since I am selecting LFEto LFE in the DOWNMIX LEVELS area , in the OUTPUT MODES area, should I select DECODE(Front/Rear) 3/2? I know that LAME has --lowpass switch. Can that work with Azid as well?

Thank You.
ddawes is offline   Reply With Quote
Old 5th February 2007, 11:32   #2  |  Link
Skelsgard
foobaring my ass off
 
Skelsgard's Avatar
 
Join Date: Nov 2005
Location: Argentina
Posts: 618
Quote:
Downmixing 6ch wav to 5.1 ac3 using BeSweet.
1) If your source has the same channel number than your output, then youŽre not downmixing nor upmixing (6ch --> 5.1, where 5+1=6).
2) DonŽt use BeSweet for AC3 encoding, its ac3enc.dll is a low quality encoder.

Quote:
Is there a CLI switch that I may use to control whatever the preset freq is for the lowpass filter to LFE?
No, at least not in any encoder at this moment.
Lowpass filters for LFE in AC3 are about 120 Hz (should ask what frequencies Aften developers are using for lowpass), though Vegas, in its project settings has an option for setting the lowpass to use with the LFE channel , and offers 4 choices:
- 80 (Dolby consumer/DVD)
- 116 (DTS)
- 120 (Dolby pro/film)
- 180

Quote:
I would like to remove bass from all other channels and send directly to LFE. I can set that from the BeSweet GUI "Azid 1" settings page, correct, by checking "LFE to LFE output" box?
Nop, that setting is not for that.
LFE to LFE Output controls the gain the LFE channel will have if directed to the LFE output(as in no downmixing of the LFE into other channels is being done). 0 gain (no gain) means the LFE will go untouched to the LFE output of the output file.
If you want to send the low frequencies from all the channels to the LFE, youŽll need an advanced audio editor with some frequency filtering capabilities.

Quote:
Also, since I am selecting LFEto LFE in the DOWNMIX LEVELS area , in the OUTPUT MODES area, should I select DECODE(Front/Rear) 3/2?
You don't need azid in your command line as youŽre encoding to ac3 with besweet, which uses the -ac3enc() command, and azid is an AC3 decoder.
Code:
BeSweet.exe -core( -input 6ch.wav -output 6ch.ac3 -logfile BeSweet.log ) -ac3enc( -b 448 -6ch )
Quote:
I know that LAME has --lowpass switch. Can that work with Azid as well?
Azid doesn' have a lowpass filter like the one you need.

Cheers
__________________
"Damn, respect my authoritay!!" - E. Cartman
Skelsgard is offline   Reply With Quote
Old 5th February 2007, 14:12   #3  |  Link
ursamtl
Registered User
 
Join Date: May 2004
Location: Montreal
Posts: 729
Quote:
Originally Posted by ddawes View Post
I would like to remove bass from all other channels and send directly to LFE.
Just remember that if you do remove frequencies and send them only to the LFE, and then use the file to create a DVD or surround CD, these frequencies will be completely lost for playback on Dolby Pro Logic systems, as the LFE data is discarded.
ursamtl is offline   Reply With Quote
Old 5th February 2007, 14:34   #4  |  Link
ddawes
Registered User
 
Join Date: May 2006
Posts: 8
Thank you very much indeed for the helpful info. You've helped me make better sense out of what I'm doing, and that says alot, lol.
ddawes is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 07:30.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.