Convolver DSP plug-in for Windows Media Player 10 - Page 5

Sure, but you could presumably write your own filter just as NVIDIA, Intervideo et al have done and add the sound processing in there. (Perhaps even some of the DScalers already done this.)

TT contains an NVIDIA decoder and so I suspect that MCE uses that, rather than TT itself. (This is based on speculation, rather than direct experimentation.)

But mymovies effectively pushes MCE out of the way and runs TT?

Rolling your own, is indeed, as your smiley suggests, a bit of a tall order...

convolver 2.12 is now up on http://convolver.sf.net

This now contains the first version of ConvolverFilter which provides an alternative, but functionally equivalent, DirectShow filter to ConvolverWrapper.

This now shows up as a DXFilter in applications such as Adobe Audition.

Enjoy.

and 2.13 ...

Automatic zero padding of filter lengths for optimal FFTW performance

The distribution package registers ConvolverFilter

I've also added ConvolverFilter.filterdata and ConvolverWrapperDMO.filterdata files for Zoom Player Pro

2.14 corrects a bug introduced in 2.12 that stopped the plug-in from functioning

Quick poll:

I note that many of the impulse response freely available on the net are stereo wavs. At present, convolver only accepts mono impulse response files (which are applied to the sum of 1 or more input channels) and the results summed to produce the output channels specified in the config file.

To add a little more flexibility (and save having to split the stereo wavs) I propose to add to the config file a line after each impulse response filename specifying which channel should be take from that impulse response file.

I realise that this will be just extra clutter for those generating their (mono) impulse respone files using DRC, but I think that it may, on balance, be worth it.

Yes, mono would still be possible, but you would have to add a 0 on a new line afer each filter filename to say "take the first channel".

(I realise that this is not v elegant, but I am reluctant to spend a lot of time on building a smarter config file parser when I hope to replace the config file with a user interface when the basic architecture is stable.)

That's right. Any libsndfile-compatible format is acceptable for Impulse Responses, with the proviso that raw .pcm or .PCM files are interpreted as 32-bit mono floats.

Convolver 2.15 is now up on http://convolver.sf.net

This allows multi-channel filter files to be used (specifying which channel is to be used for a filter path through the config file) -- so you can use all those stereo impulse files available on the internet, for example. Note that existing config files with mono filters will need to be edited to add a single line containing 0 after each filter file name.

It also allows tuning rigour to be set through the properties page.

Negative scaling factors are allowed (which will result in phase inversion). For straight inversion, don't use -0.0 for channel 0; use -0.99999 instead.

There has also been a good deal of internal refactoring and cleaning up for future optimization (so I would be particularly grateful for those interested in giving convolver a thrashing, as the testing needs to be much more extensive).

As ever, feedback welcome. In particular, I have been considering putting on a windows interface to replace the config text file approach.

Other feedback that I have had suggests, however, that the text file approach is straightforward even for the inexperienced, with the consequence that I would be better spending my time on

- making the config file parser more robust / helpful in its error messages and concentrating on features such as

- delay (not clear what that means yet), and

- the ability to select different configs automatically, depending on the input sample rate / channel numbers

for example.

The windows interface would be quite a lot of work and it is not clear that it would make convolver much easier to grasp (essentially because for each filter path you still need to specify

- the input channels and scaling factors to be applied to them;

- the impulse response file that is to be used (and which channel from that file)

- and the output channels are to receive the output (again with scaling factors, and the assumption that the outputs from different filter paths to a particular channel are summed)

I don't really want to spend time on the interface until convolver is feature complete.

However, I am open to persuasion about priorities.

Wes,

Check out www.duffroomcorrection.com which has pointers to methods both for cross-over generation and impulse response generation.

ACXO output should be usable, as should rec_imp (http://www.duffroomcorrection.com/wi...Measuring_Tool)

I've had a go at compiling up rec_imp and there are indeed problems with the RTAudio library that it uses. I will pop a version that uses only DirectSound in with 2.16, which will contain some smalll optimizations, unless someone comes up with some show-breaking bugs with 2.15.

2.16 is now up on http://convolver.sf.net

It contains some internal optimizations over 2.15

2.16i is compiled with the Intel C++ compiler, 2.16 with the VC++ 2003. The former *may* be faster if you have a newer CPU. I'd be interested in hearing reports of any differences that you find.

I attach a DirectSound version of rec_imp (no ASIO support) for generating impulse response files. See http://www.duffroomcorrection.com/wi...Measuring_Tool for more details. No guarantees. The RtAudio library still seems to contain some bugs, but it works for me on a couple of different machines. I'll do a little more work on this, so feedback would be welcome.

 

rec_imp.zip 136.2021484375k . file

I've compiled up separate DS and ASIO versions of rec_imp and put them on http://www.duffroomcorrection.com/wi...Measuring_Tool

The ASIO version is still flakey, but see how you get on.

Coming soon: I am adding the capability to specify a list of filter paths (ie, a list of config files) which will be tested in turn and the first to match the input stream (no of channels, sample rate) will be used.

I am hoping that this will make Convolver more usable with, eg, DVDs where the source format can change from stereo to 5.1 and back again on some DVDs.

I will also try to allow the specification of filter paths that by-pass convolutiuon.

For those of you that have managed to get something usable working, it would be helpful to make a contribution either here or on http://www.duffroomcorrection.com/wi...Player_plug-in (so that others can learn from our experience) setting out your filters (and how you generated them), configuration files and equipment.

Equally, you might want to highlight any show-stopping usablity features (including complexity, I know).

Thanks for the feedback, and glad that you have got rec_imp working on your setup.

Convolver is able to read .pcm files, interpreting them essentially as a sequence of 32-bit floats, which means that they can provide an impulse only for a single channel / filter path.

This means that if you are using stereo, or multi-channel, you will need a series of .pcm files to do the job (as you correctly surmise).

There are different schools of thought about how best to do this. Eg for a stereo setup:

i) record mono impulses from each speaker separately and apply them to the corresponding channel -- the method that you are outlining;

ii) record stereo impulses L-LR and R-LR and apply the sum of convolved L-L and R-L to the left channel, and of convolving L-R and R-R with the right channel. (See http://www.ramsete.com/aurora/waveconv.htm for a schematic diagram)

Let us know how you get on.