Question - Duplicate left to right channel of sound

jirim100

Member
Please, I very often edit videos (from DVD disks) which have dual channel sound (for example type of AC3) but is heard only left or right channel. Is it possible to duplicate left channel to right channel (or vice versa) and leave the same input encoding (for example AC3)?
 

Dan203

Senior Developer
Staff member
One correction.... The Pro version has the ability to remap and duplicate audio channels however it does NOT have the ability to save those remapped streams to AC3. We do not have a license to encode AC3 audio. So once you remapped the channels you'd have to save the audio to MP2 or PCM instead.

Yes the Pro version is the $200 upgrade you mentioned before. It has a bunch of features that mainly only apply to the broadcasting and syndication industry so we don't recommend it to average users unless you really have a need for one of those features.
 

jmc

Active member
Please, I very often edit videos (from DVD disks) which have dual channel sound (for example type of AC3) but is heard only left or right channel. Is it possible to duplicate left channel to right channel (or vice versa) and leave the same input encoding (for example AC3)?
I use Audacity to alter audio streams that VRD will not (like AC3).
You do Elementary Streams then Mux the video component and Audio Stream wanted
back together.

http://audacity.sourceforge.net
(you will find instructions on the hoops you have to jump through to get AC3 working in it
on the Audacity home page)


jmc
 

jirim100

Member
My simple workaround for this problem is convert this AC3 audio to "MPEG layer 2" audio with one output channel. Then both, left and right repro emit sound.

For me is not important AC3 output format.
 
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jmc

Active member
My simple workaround for this problem is convert this AC3 audio to "MPEG layer 2" audio with one output channel. Then both, left and right repro emit sound.

For me is not important AC3 output format.
I'm not very sensitive to audio changes, can change it all around and notice nothing quality wise.

But one element that may or may not matter to you is that MPEG audio may be twice the
size of AAC or AC3 audio.

jmc
 

jirim100

Member
But one element that may or may not matter to you is that MPEG audio may be twice the
size of AAC or AC3 audio.
No, this is not true. For example now I converted movie of length 01:14:37 and according to MediaInfo:
- original dual channel of AC3 audio has size 137 MB (whole size of movie is 1 271 120 051 bytes).
- after conversion one channel of MPEG audio has size only 69 MB (whole size of movie is 1 200 728 861 bytes).

My conclusion is that both compression is roughly the same (size one channel of AC3 is roughly the same as size of one channel of MPEG audio).
 

Dan203

Senior Developer
Staff member
I'm not very sensitive to audio changes, can change it all around and notice nothing quality wise.

But one element that may or may not matter to you is that MPEG audio may be twice the
size of AAC or AC3 audio.

jmc
Audio bitrates are pretty insignificant to the total file size. We're talkeding about 128-256kbps. Compared to the video bitrate that's a tiny fraction. The only one that makes the size jump significantly is PCM and that's because it's over 1.5Mbps.
 

jmc

Active member
Audio bitrates are pretty insignificant to the total file size. We're talkeding about 128-256kbps. Compared to the video bitrate that's a tiny fraction. The only one that makes the size jump significantly is PCM and that's because it's over 1.5Mbps.
Glad you mentioned bitrates.

My test files showed MPG audio to be twice the size of AC3 but
your message made me realize that I had paid no attention to
the bitrate etc of my test encodes... sloppy on my part.

thanks,
jmc
 

jirim100

Member
Please, exist any chance to detect zero volume (no sound) in left or in right channel programmatically? Exist any program which can do it from commnad line?
 

MrVideo

Active member
Please, I very often edit videos (from DVD disks) which have dual channel sound (for example type of AC3) but is heard only left or right channel. Is it possible to duplicate left channel to right channel (or vice versa) and leave the same input encoding (for example AC3)?
I've never heard of a professionally produced DVD having stereo audio but only putting the audio in one of the two channels. That would, IMHO, pissed off a lot of people.

What is the source of these DVDs?
 

jirim100

Member
What is the source of these DVDs?
They aren't professional DVDs. They are created/burned in home DVD recorders.

But I found how to resolve this problem - simply converting stereo sound to mono sound, then both, left and right speakers are heard.
 
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