How Do I Write a Filter with no clip argument

[scmccarthy]

I started writing a filter that creates color bars in YUY2 instead of RGB. But I stuck it in an old script I was using to test an RGB conversion filter.

After I got it working, I created an example script for it and discovered my problem. It won't work unless I open a clip even though it does nothing with the clip.

Once I remove the IClip* argument, GenericVideoFilter does not have a valid argument and can't be used.

So the real question becomes: How do you replace GenericVideoFilter or the argument it needs?

Stephen

[dividee]

When writing a source filter, it's better to inherit from IClip directly, not from GenericVideoFilter. Don't forget to initialize vi yourself then, and to implement each pure virtual function of IClip.

[scmccarthy]

@dividee

I was hoping I could side step implementing each pure virtual function. There are four of them now:

GetParity(int)
GetAudio(void *,__int64,__int64,IScriptEnvironment *)
SetCacheHints(int,int)
GetVideoInfo(void)

I tried this before after looking at source.cpp. Is this how I should start it then?

#include "avisynth.h"
class ColorBars_YV12 : public IClip {
VideoInfo vi;
public:
ColorBars_YV12(int _w, int _h) {
vi.width = _w;
vi.height = _h;
}
PVideoFrame __stdcall GetFrame(int n, IScriptEnvironment* env);
};

Stephen

[scmccarthy]

Here's an update of my progress. This sort of works:

#include "avisynth.h"
class YUVColorBars : public IClip {
VideoInfo vi;
public:
YUVColorBars(int _h) {
vi.width = 720;
vi.height = _h;
vi.fps_numerator = 4;
vi.fps_denominator = 1;
vi.num_frames = 188;
vi.pixel_type = VideoInfo::CS_YUY2;
SetCacheHints(CACHE_NOTHING,0);
}
PVideoFrame __stdcall GetFrame(int n, IScriptEnvironment* env);
bool __stdcall GetParity(int n) { return false; }
void __stdcall GetAudio(void* buf, __int64 start, __int64 count, IScriptEnvironment* env) { }
void __stdcall SetCacheHints(int cachehints,int frame_range) { };
const VideoInfo& __stdcall GetVideoInfo() { return vi; }
};


Media Player trys to download an activex component and then goes ahead and plays the clip.

Stephen

[dividee]

Media Player trys to download an activex component and then goes ahead and plays the clip.

That's probably because you forgot to tell that the clip has no audio:
vi.audio_samples_per_second = 0;

[scmccarthy]

I am going to post before I try it. Certainly, that is right.

Thank you very much.

Trying to follow the internal ColorBars as an example didn't work, because it has audio.

Stephen