ac3 with Dolby Surround tag?

[Laryllan]

Yes, I want to create an ac3-file with a Dolby Surround tag so that my external Dolby Surround decoder can decode it properly.

I´ve tried ac3machine and Besweet but none of them is able to write this tag. So all ac3 streams transported to my decoder are decoded in 2-channel stereo mode.

SoftEncode could probably do this but it doesn´t work on my system. (crash)

for example: I decoded an 5.1 channel ac3 with azid in surround mode and want to encode it in ac3 format signed as DS.

[OvERaCiD23]

If it's encoded with the Surround (DPL) downmix in BeSweet, all you need is a player/receiver that has Dolby Pro Logic. It will recreate the sound, as it was encoded for this (5.1 to 2, using the surround downmix). I do not believe there is a tag for this, it just needs to be encoded properly (as DPL can recreate surround from any 2ch source, for it to work as intended the source must be properly encoded).

[Laryllan]

There is a tag for this at the beginning of every ac3 file.
How else could a decoder distinguish Dolby Surround from Stereo?

[DJ Bobo]

In "Sonic Foundry Soft Encode" you can specify that the stream is Dolby Surround encoded.

But it's not necessary. Even if you encode with an "unknown" tag, just push the "pro-logic" button on the remote control of your receiver and it will work properly.

[Laryllan]

My Dolby Digital decoder is a Creative one - maybe one of the cheapest ever built. :( And as I said it enables ProLogic decoding automatically if it reads the tag in an ac3 stream. If there is no tag, the stream is played back as it is - mostly plain stereo. Enableing ProLogic decoding while playing ac3 is simply not possible.

So, maybe one of the programmers of an ac3 transcoding/encoding tool is reading this: this is kind of a feature request - a feature easily implemented (at least I hope so). Just write "Dolby Surround encoded" in the bitstream information of the new ac3 file...

[DSPguru]

try this out.

[Laryllan]

It works.
But output volume gets terribly low (using ac3machine).

Is it possible to get this one as an .exe to play around with?

[DSPguru]

exe of what ?

[Laryllan]

an .exe of ac3encoder.dll

btw, what to do about the low volume when encoding to surround?
Is it possible ac3encoder uses the dialog level at -27dB by default? I´ve tried decoding with acid to .wav (sounds volume is good) and then reencoding to ac3 using ac3machine (not using any options but channels mode surround) -> volume gets low in the encoded ac3. No options in ac3machine work to prevent it, neither any setting in "gain" nor SSRC does the trick.

That´s why I would like ac3encoder.dll as .exe, I could see the command line switches and do further testing. Hope it´s possible, sounds a bit lamer-like, I know.

[DSPguru]

don't have time for this.

the source-code can be found at http://ffmpeg.org

edit : direct link -
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/ffmpeg/ffmpeg/libavcodec/

[Laryllan]

You have no time for what? The CommandLineClient is not important, leveling the sound output of the ac3encoder would be appreciated. And I am not the only one having this problem.

[DSPguru]

Originally posted by Laryllan
I am not the only one having this problem. i'm not the only developer around here, either.
the source-code is accesible to everyone.

stop demanding! i have a very dense time in my persOnal life at the moment (quit my job, etc'..), and what do you know.. my personal life comes first :o.

[Laryllan]

Sorry, didn´t want to seem rude. Your life comes first.

Thanks for your help anyway! :rolleyes: