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Old 24th March 2018, 00:06   #1  |  Link
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Join Date: Jul 2014
Posts: 758
Implementing dual Vapoursynth/Avisynth filters

In coding a single DGDecodeNV.dll to support native use by both Vapoursynth and Avisynth(+) I run into practical matters that I hope you may be able to suggest some good approach for. The issue is to avoid unnecessary code duplication.

For example, in Avisynth GetFrame() is nonstatic and has access to its class variables directly. In Vapoursynth, GetFrame() is static and receives an instance pointer. So I have vs-> references throughout the GetFrame() code but not for Avisynth, making it very hard to use common code. There are some other similar things but I'll concentrate on this for now.

I've been able to 'commonify' the other calls but GetFrame() is looking difficult. Naturally, I don't want to duplicate large chunks of code just to add vs-> to all the member references, etc.

Any ideas would be appreciated and could help others to make good dual plugins. Thank you.
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Old 24th March 2018, 00:15   #2  |  Link
Stephen R. Savage
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Posts: 341
Try to make a filter class that is independent of VS and AVS APIs.

class MyFilter {
    MyFrame GetFrame(/* ... */);

class MyAvsFilter {
    MyFilter *pFilter;
    PVideoFrame GetFrame(/* ... */)
        MyFrame frame = pFilter->GetFrame();
        PVideoFrame avs_frame = /* ... */;
        return avs_frame.

struct MyVsFilter {
    MyFilter *filter;

VSFrameRef *vs_get_frame(/* ... */)
    MyFilter *filter = ((MyVsFilter *)instanceData)->filter;
    MyFrame frame = filter->GetFrame();
    VSFrameRef *vs_frame = /* ... */;
    return vs_frame;
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