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Up-mixing stereo to 5-channels

I want to up-mix some stereo audio streams to 5 channels.
All of these stereo audio streams have been converted from their 5.1 version to stereo.
Now, I just want to get the surround effect back.
So, basically, the problem is as follows:

5.1 Stream --------> Stereo --------> 5.0 Stream

While I understand that the resultant 5.0 stream won't give as much surround effect as the original 5.1 stream, but, it sure would be better than stereo.

According to FFMPEG,
"ffmpeg integrates a default down-mix (and up-mix) system that should be preferred (the -ac option) over the pan filter unless you have very specific needs".
I couldn't figure out the default up-mix system provided by FFMPEG.

What I'm looking for is something similar to what Dolby Pro Logic II does. If a Dolby Digital Decoder knows that the down-mixed stereo will ultimately be converted back to surround audio, then it converts to Lt/Rt (which is termed as left total and right total by Dolby), as mentioned on Page 12 here:
http://www.dolby.com/us/en/technologies/a-guide-to-dolby-metadata.pdf

Is there anything similar to this that can be done?


Re: Up-mixing stereo to 5-channels

Reply #2
I tried this, for a while: https://en.wikipedia.org/wiki/Hafler_circuit Simple enough for even me to wire up without the loss of many lives.

My current living room is not suited for using it, on grounds of space and placement of various immovable objects. And I was happy with 2-channel stereo, really.

But it was an interesting effect to try out for a while. And it doesn't require the purchase of extra electronics or soldering - unless you feel the need for a resistor or volume control - just plenty of wire.

Re: Up-mixing stereo to 5-channels

Reply #3
Quote
What I'm looking for is something similar to what Dolby Pro Logic II does.
It would make more sense to simply play it back on a system that can decode Dolby Surround (Pro Logic).     Any 5.1 channel setup that can play 5.1 DVDs or Blu-Rays should have Dolby Surround decoding and there's no reason* to up-mix it in advance of playback.    

But, if it was simply downmixed without being properly encoded it's unlikely that you'll get good results with the Pro logic Movie Mode and you'll probably need to use one of the other soundfield options that are designed for regular stereo.



* The exception would be if you wanted to do your own editing, panning, delay, EQ, etc, with the individual channels.     I did that once or twice with concert videos, converting a mono track to surround.    For example, I used some stereo-simulation effects, panned the talking between songs to the center, and copied applause from various parts of the recording and mixed it into the rear channels so it was added to the existing regular-stereo applause in the front channels (maybe while fading-down the front channels a bit), etc.

Re: Up-mixing stereo to 5-channels

Reply #4
Quote
What I'm looking for is something similar to what Dolby Pro Logic II does.
It would make more sense to simply play it back on a system that can decode Dolby Surround (Pro Logic).     Any 5.1 channel setup that can play 5.1 DVDs or Blu-Rays should have Dolby Surround decoding and there's no reason* to up-mix it in advance of playback.    

But, if it was simply downmixed without being properly encoded it's unlikely that you'll get good results with the Pro logic Movie Mode and you'll probably need to use one of the other soundfield options that are designed for regular stereo.



* The exception would be if you wanted to do your own editing, panning, delay, EQ, etc, with the individual channels.     I did that once or twice with concert videos, converting a mono track to surround.    For example, I used some stereo-simulation effects, panned the talking between songs to the center, and copied applause from various parts of the recording and mixed it into the rear channels so it was added to the existing regular-stereo applause in the front channels (maybe while fading-down the front channels a bit), etc.

This. Id just run the stereo into a receiver that can do Dolby ProLogic surround processing and it will upmix for you in real time.

Re: Up-mixing stereo to 5-channels

Reply #5
It would make more sense to simply play it back on a system that can decode Dolby Surround (Pro Logic).     Any 5.1 channel setup that can play 5.1 DVDs or Blu-Rays should have Dolby Surround decoding and there's no reason* to up-mix it in advance of playback.


The reason is that I'm limited by bandwidth in what I'm trying to do. I need to transmit only stereo and not more than that.
That is why I want to downmix the 5.1 stream in a way so that least surround information is lost.
You're right, the downmixing also has to be done accordingly, so that the surround channels are obtained during the post-processing, at the receiving end.
So, from what I understand, are you trying to say that I should be using a Dolby Pro Logic Encoder on the transmitting side, and a Dolby Pro Logic Decoder on the receiving side?

Re: Up-mixing stereo to 5-channels

Reply #6
It would make more sense to simply play it back on a system that can decode Dolby Surround (Pro Logic).     Any 5.1 channel setup that can play 5.1 DVDs or Blu-Rays should have Dolby Surround decoding and there's no reason* to up-mix it in advance of playback.


The reason is that I'm limited by bandwidth in what I'm trying to do. I need to transmit only stereo and not more than that.
That is why I want to downmix the 5.1 stream in a way so that least surround information is lost.
You're right, the downmixing also has to be done accordingly, so that the surround channels are obtained during the post-processing, at the receiving end.
So, from what I understand, are you trying to say that I should be using a Dolby Pro Logic Encoder on the transmitting side, and a Dolby Pro Logic Decoder on the receiving side?

Just give the receiver a stereo signal and let it do upmixing to pro logic itself. My Yahama AV receiver done it, and so does my Denon AVR-X1200. I can give it stereo audio from any source I want and select a DSP such as 5 channel stereo, Dolby PLII etc...., the upmixing is done in receiver.

Re: Up-mixing stereo to 5-channels

Reply #7
You could try DTS Neural UpMix. I had nice results with it on regular stereo CDs.

Cheers
If age or weaknes doe prohibyte bloudletting you must use boxing

Re: Up-mixing stereo to 5-channels

Reply #8
It depends whether your file has been downmixed or if it still contains the original 5.1 stems. Upload a file and I can tell you.

 
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