[MPlayer-dev-eng] [PATCH] Proof of concept extrasurround plugin

[Stephen Davies]

On Thu, 4 Apr 2002, Anders Johansson wrote:

> Try using my lowpass filter you find it in libao2/fir.h. It is
> assembly optimized and quite easy to use. Have you read the specs of
> how steep and how long the filter should be? Guess you will find them
> in the dolby surround specifications. According to Steve Davies who
> wrote the plugin the filter needs to be quite long to sound well. I
> will be happy to help you out with using the FIR filter. We could
> replace the other filters in this plugin as well while we are at it.

Hi - the thing with fir filters is that you need a lot of taps to get a
steep roll-off at a low frequency.  That may be fine with the asm filter
you wrote but my C version wouldn't be fast enough.

So I agree to replace the filter with yours.  I haven't looked at it.  One
question in my mind is whether it will be compatible with the coefficient
calculating that I do.

> We might want to use this even if there is no surround sound
> information just to generate the necessary sub-woofer channel. That
> would make the sound a lot better on cheap surround sound systems,
> where the front L and R speakers are small.

Don't speaker systems like that usually do that bass diversion anyway?  As
you can tell I only have 4 speakers!

Steve