Request advice for 6-chan AC3 to 2-chan AC3 transcoding?

[LisaB]

As far as I know, BeSweet has a poor quality AC3 encoding engine, and ffmpeg has a good quality AC3 encoding engine....

However, if I use Batch ffmpeg GUI XP with a 6-chan AC3 as source file, will it do all the proper downmixing of the channels?

I have done very little 6-chan to 2-chan transcoding, and so I am not sure about the complexity of mixing, or how to set parameters.

I assume that there is some very special channel mixing that goes on, since you would not want to just take the L and R channels out of the source file and discard all the other channels.

I have certainly heard some stereo encodes where the voices seemed to be swallowed up by the background noise, and I assumed this was probably the result of a poor mixing job when transcoding from a 6-channel source.

Any advice on 6 to 2 channel encodes is appreciated.

[guns1inger]

If you really want to mix it properly, demux out to 6 mono wavs. load them up into your audio editor and mix down until you have a happy stereo track, then encode this. Vegas would let you mix down all 6 channels together and output a 2 channel AC3.

From what I read here, BeSweet seems to have put most of it's encoding problems behind it, so maybe you are being harsh. Of course, you could try for yourself and report back. Then everyone would learn something.

[LisaB]

If you take a look at the BeSweet homepage,

http://dspguru.doom9.net/

and click on the "FAQ" button, you will notice that item 16 of the official BeSweet FAQ reads as follows:

"ac3enc.dll creates (almost) useless ac3 streams. don't use it to encode things you care for. it's there only for test purposes."

Now, perhaps there is a way to encode AC3 with BeSweet without using the ac3enc.dll.....or maybe the ac3enc.dll has been fixed, and just not updated in the official FAQ....

But, this is why I am very skeptical about the ability of BeSweet to produce high quality AC3 encodes.

[guns1inger]

If you want a quality encoder then get an official licensed AC3 encoder. Pegasys have a 2 channel encoder, Sony have a 5.1 EX encoder, Surcode also have a 5.1 EX encoder. It is the only way to guarantee your outcome.