ConvertFPS( ) doesn't work on DVD (.d2v) input?

[augi]

I try to include ConvertFPS() in a .avs script for processing a DVD. The scipt is :

LoadPlugin("C:\dvd\utilz\GORDIA~1\mpeg2dec3.dll")
LoadPlugin("C:\dvd\utilz\GORDIA~1\undot.dll")
mpeg2source("C:\dvd\movies\mona\mona.d2v")
crop(0,22,716,532)
LanczosResize(688,352)
ConvertFPS(20)
Undot()

When I try to open it with VirtualdubMod, there is an error: "ConvertFPS: requires YUY2 input".
That means that convertFPS can't filter a DVD stream?

[Guest]

Add ConvertToYUY2(interlaced=false) before your ConvertFPS() call.

I assume that your video is progressive, because you resize without deinterlacing.

[augi]

Ok thanks. I'll do that. My video is progrsessive.

I have another question. I ran ChangeFPS(20) instead of ConvertFPS(20) and it worked OK. Same thing wiht WirtualDubMod's filter for fps conversion. The strange thing is this: my original movie clip was 25fps and had 4500 frames with each frame having a duration of 0.04 sec (1/25 sec). The final movie after the fps conversion had 3600 frames with 0.05 sec (1/20 sec) duration each. The 3600 is the outcome of : 20/25*4500=3600 frames

BUT, the size of the .avi file was not : 20/25*original size
Instead it was only decreased by 4% (not 20% that 20/25 gives).
Why is that? Given that I reduce the number of frames my video contains, that doesn't meen I reduce the amount of information and that should produce a smaller avi file?

[Guest]

The final file size depends also on the type and amount of compression you apply during the final encoding.

[augi]

In both cases I apply the same compression : DivX codec , 5.5 Mbps, 2pass. I can't understand why the file size is not by 20% smaller. As I give less frames to the codec, with each frame having a longer duration, it should produce a .avi file with size proportional to the frame number reduction (3600/4500=20/25=20% smaller). The vompression bitrate is the same for both cases...
Anyway, I do all that as part of my dioploma thesis. I am measuring the efficiency of a Wlan under multimedia services. I want to see how the same video, streamed over the wlan with different fps, bahaves (packet loss, delay). I was expecing thath by reducing the fps, the size would reduce, as my final goal is to make the video more easy to stream over the wireless lan.

[Guest]

The total duration of your video remains the same, so the product of duration and bitrate remains a constant as well! That means the filesize remains constant too. :)

[scharfis_brain]

but note: using blending to convert between framerates, will result in lesser compressibility, because ghosting means more complexity to an encoder.
also, a 30->20 blendconversion might result in juddery motion