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View Full Version : How are AVI frames provided to encoder?

Prettz
1st February 2003, 21:36
When you open up an AVI file in VirtualDub, Nandub, or Avisynth (using AVISource()), who decodes and provides the input frames?
Say I have ffdshow installed and I open up an xvid avi in VirtualDub, does ffdshow provide the frames to VirtualDub? If so, would its postprocessing options be applied to each frame?
sh0dan
1st February 2003, 21:38
The VFW codec is used, when using AviSource. This will be the same codec as when opening the file in vdub.
Directshowsource will use the directshow filter.
Bidoche
2nd February 2003, 00:33
As far as I know, the code of avisource is mostly borrowed form Vdub, no ?
sh0dan
2nd February 2003, 01:41
Right - and adapted by dividee!
ErMaC
2nd February 2003, 03:17
To explain a bit more behind your question, here's what happens:

FFDShow is a DirectShow filter. AVISource uses the VFW interface, so ffdshow is not involved at all in the process. If you do want to take advantage of ffdshow's PP abilities as a preprocessor before the frames enter AVISynth, you can use DirectShowSource() on the file, and if MediaPlayer plays back that AVI file via ffdshow, then AVISynth will read in that file via ffdshow. Note, however, that then seeking becomes an issue since you can't seek backwards properly in Dshow.