[Request] Add a matrixed stereo decoder (e.g. Pro Logic II) to LAV Audio Decoder

[E119E]

LAV Audio Decoder can downmix a multi-channel source to 2.0 stereo and encode it with Dolby Pro Logic II matrixed surround sound that can be decoded by an A/V receiver. However, it can't do the opposite -- decode a matrixed stereo source into 5.1 surround. There are older movies that are getting released on new formats with matrixed stereo tracks, so this would be a nice functionality.

It should be easy to add, LAV Audio Decoder already has a Pro Logic II encoder, just add the option to reverse the process. Then you can let the user decide if they want to run it by default on all stereo sources or have the option to select it when they want to.

A more advanced functionality would be to detect whether the stereo source contains matrixed surround (and what it is exactly) and decode/upmix it automatically, and if not keep it as stereo. This may be harder to implement, but it would be more useful.

Edit: An example of a Pro Logic II decoder is the foobar2000 FreeSurround plug-in.

[tebasuna51]

I don't know how detect whether the stereo source contains matrixed surround, the only coded than have a flag to indicate this is the AC3, all other codecs can't be detected on the fly if are dpl coded.

If an stereo AC3 flaged like dpl coded is passed to AVR must be automatically decoded to surround.

If you suspect than any other stereo format is dpl II encoded use the FreeSurround plugin of foobar2000 to convert it to surround or activate manually the dplII decoder of your AVR.

Implement that request in LAV Filter is a hard work without many usage.

BTW if the developpers are interested the FreeSurround plugin is a good aproach: http://www.hydrogenaudio.org/forums/index.php?showtopic=52235

Here there are also some interesting info: http://forum.doom9.org/showthread.php?t=112122