Encoding mono audio

[tiresias]

I am encoding some VHS footage to DVD. As it is quite old the audio is from the mono VHS track. It seems a waste to encode mono as stereo but I can't see any mention of encoding a single mono channel rather 2 channels, one of which is effectively useless and would be better used slightly increasing the video bitrate. Is there a way to encode a single mono channel, or are there any tricks for encoding mono efficiently.

[Asmodeus]

MP2 or AC3 support single chanell mode compliant with DVD standard.
For VHS source you can use MP2 at ~64kbps (try also 56). I think it will be enought.

[joshyg2]

If you are using the audio for DVD, just encode the audio as MONO AC3, I use SonicFoundry Soft Encode.

Very good program, but you can't purchase it anymore, I was lucky.

But you can also go for MPEG1 Layer 2, but AC3 is better.

[Asmodeus]

Acording to all coments on this forum (and my private tests), there is no quality difference betwen low bitrate stereo (or mono) MP2 and AC3, and BeSweet does good job with mp2enc. ac3enc is still not as good in quality, maybe SFSE is, but I don't use it.
So I sugest MP2 mono encode with BeSweet which is of course much much much cheaper than SFSE ... in fact it is free :D

[colinb]

Thanks. So AC3 mono is possible. I'm using BeSweet with AC3Machine GUI. AC3Machine does not appear to have a mono encoding mode selectable. Is this a failing of AC3Machine or does BeSweet itself not support mono? If BeSweet does support mono then I guess I'll have to run it directly from the command line.

[Asmodeus]

AC3 mono is possible, but BeSweet has no option for that. It's uses 5.1 or stereo. I've tryed encode mono to AC3 and it outs stereo :confused: AFAIR FFmpeg can encode to AC3 mono, but it uses PCM as input. But, as I already sugested, AC3 mono at low bitrate will have no beter quality than MP2, specjaly if it is talking (non music video) source. For sure there will be no difference if source is VHS.

[joshyg2]

I agree Asmodeus, that AC3 wont have much better quality, than MPEG1 Layer 2 with MONO audio, but MP2 dosn't have features like, Dialog Normalization, Dynamic Range Compression, RF Modulation Protection, etc.

With AC3 all this important audio information is stored within the stream.

[tiresias]

Interestingly if you feed a mono WAV file into BeSweet it does seem to output a mono AC3 file. Unfortunately it plays at half speed (although correct pitch) so is completely useless.

In another thread someone said that they thought that a mono track would just come out of the centre speaker, while some people would prefer it to come out of the left and right speakers (like traditional stereo equipment) even though it is mono.

In that case I'll stick to encoding it as stereo.

Thanks for the comments.

[hendrix]

mp2 is fine if youre a PAL user but it isn't a NTSC standard...true there are NTSC DVD players that can play them but most do not...i say stay with the standard.

[joshyg2]

really, not in the NTSC DVD standard ? i thought it was

oh and, never i mean never use BeSweet to Encode AC3, the quality is bad.

use a Licenced Dolby(c) Digital software encoder, whether it is SonicFoundry Soft Encode, or Sony Vegas. these programs give you crystal clear Dolby Digital AC3, whether it is:

* 1/0 (C)
* 2/0 (L,R)
* 3/0 (L,C,R)
* 2/1 (L,R,l)
* 3/1 (L,C,R,l)
* 2/2 (L,R,l,r)
* 3/2 (L,C,R,l,r)

channels.

[hendrix]

i would use Vegas 4 or 5 over Soft Encode...

Soft Encode uses Dolby Digital Encoder v.6.2.2 - released December 2, 1997; Vegas uses version 7.

plus vegas 5 is more flexible in mixing 5.1...it lets you follow the action with key frames...very cool

i agree with joshyg2 dont use BeSweet to encode DD...i've read that it's buggy although i cant confirm since i use Vegas 5 for encoding

[hendrix]

For VHS source you can use MP2 at ~64kbps (try also 56). I think it will be enought.

when encoding a 1/0 mono track .ac3, encode @ 128kbps anything will just be wasting space

56 kbps has an audio bandwidth of 9.09 khz
64 kbps has a 10.22 khz bandwidth....which will sound worse than an old am radio - plus @128kbps hardly takes any space