Convering mono AC3 2.0 to mono AC3 1.0

[nigor]

Makes u wonder, why the hell some DVDs have 2 channel mono sound? The whole point of mono is that you have 1 channel only, and convering it to 2 channels takes up bandwith, and is simply pointless. But alas, some DVDs have it, and there is nothing I can do about that.

Anyhow, I am trying to convert a mono 2 channel track @ 192kbits/s to mono 1 channel track @ 96kbits/s using BeSweet. No matter which options I set, I always end up with 2 channel track. The best I could do was to create an ac3 2.0 track @ 96kbit/s, and yes, the quality is noticebly worse than at 192kbit/s.

I played around with 'Dual Mono' 'Stereo' and 'Decode (Front/Rear)' options under "Azid 1" in Besweet, but to no use.

So is it even possible to create an AC3 1.0 track in BeSweet?

thanx.

[pacohaas]

yes, it might be nice to have the ability to simply split off left and right (and other) channels without needing an expensive ac3 processing tool. I don't think BeSweet can do this at present though.

[OvERaCiD23]

just curious why you're trying to produce an AC3 1.0? what are you gaining from using the AC3 format to encode one channel of audio? i would just encode to MP3/OGG, but maybe you have a good reason...

[DJ Bobo]

Well, this what I would do:
1) Use AZID to convert this 2.0 ac3 to mono wav:

azid -c normal -d1/0 -oc -a filename.ac3 filename.wav

You can add a "-F wav24" if you want better quality (24-bit WAV instead of 16-bit). This supposes your encoding application supports 24-bit WAV files (Lame supports 24-bit input). If it doesn't, you've got to dither the 24-bit file to 16-bit in an application like WaveLab or something.
2) Encode to MP3 @ 96kbps for DivX delivery, or MP2 @ 112kbps for SVCD or DVD delivery.

[nigor]

Well, here is what I normally do. I decompress the AC3 file in HeadAC3he to 32 bit float wav. Then, I use OggdropXPd to convert the file into a 96 kbits/s Ogg file (OggdropXPd has the 'mono' function). This process takes up time, and you do theoretically loose quality whilst re-encoding, although I doubt anyone can hear the difference. I just hope the mono function will be introduced in Besweet in the future.

Originally posted by OvERaCiD23
just curious why you're trying to produce an AC3 1.0? what are you gaining from using the AC3 format to encode one channel of audio? i would just encode to MP3/OGG, but maybe you have a good reason...

I have ripped a DVD which has AC3 2.0 mono audio. I just wish to cut off one of the channels to reduce the filesize by half. I do not want to re-encode, cuz it takes time, and you would loose quality in the process...

[specise_8472]

My 2c worth

Just use Sonic Foundrys Soft Encode.
Open the AC3 as seperate channels (decode to pcm)
Delete 1
File Encode - AC3
DONE

[DIggedy]

I think they use 2ch DD normally so that it decodes into the 2 front speakers instead of just the centre channel (widescreen review refer to this as 'big fat mono'). Some people prefer it this way (myself included) because my centre channel can't reproduce the complete dynamics of the signal so I'd rather use my beefy fronts instead so I get all the bass etc. If it is only 1.0 you can put the reciever into stereo mode to achieve this effect, but at a quality loss because it has to downmix the signal to do so. But the people who want it in the centre channel just have to engage Pro-logic on their reciever to achieve this.

[DJ Bobo]

@ specise
The MP3 way would be better then, because MP3 is slightly better than AC3.

BTW, I would also be interested in a way, to just extract one of the 2 channels of an AC3 2.0 mono track without reencoding.