controlling resolution of mpeg-2 from a timeline

From: thomas144 (anonymous_at_discussions.microsoft.com)
Date: 05/12/04 

Date: Wed, 12 May 2004 12:01:05 -0700

Ok, I have managed to hack up the timelinetest.cpp directshow sample
to write to an mpeg-2 file from an mpeg-2 source, using intervideo's mpeg2
encoder, the intervideo mux, and intervideo mpeg-2 file writer on the back-end.

The problem I am having is that DirectShow converts the source mpeg-2 video
from 720x480 to 320x240. I can save the graph I am creating in my program
and run it with graphedit to see directshow is inserting a Resizer filter and Frame
Rate Converter filter after the MPEG2 Decoder on the front end.

I will look at fiddling with the VideoGroupType when I create the timeline. Right now
the major type is set to MEDIATYPE_Video but I haven't yet figured out how to set
the subtype to MPEG2_Video and there could I suppose be some methods in the
IAMTimelineSrc object that might be useful.

(Basically what I want to do is extract a short clip at a particular start and stop time
from a much larger MPEG2 file and write that clip to an individual MPEG2 file.)

I've also noticed that there is support for writing my own resizer filter, but I guess
my working hypothesis is to try to understand why "ConnectFrontEnd" thinks it needs to
resize my source video in the first place.

Comments? Hints? Clues? Am I on the right track?

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