How to feed video data into a DirectShow filter to compress/encode and save to file?

Question

First of all, here is what I'm trying to accomplish: We'd like to add the capability to our commercial application to generate a video file to visualize data. It should be saved in a reasonably compressed format. It is important that the encoding library/codecs are licensed such that we're allowed to use and sell our software without restriction. It's also important that the media format can easily be played by a customer, i.e. can be played by Windows Media Player without requiring a codec pack to be installed.

I'm trying to use DirectShow in c++ by creating a source filter with one output pin that generates the video. I'm closely following the DirectShow samples called Bouncing Ball and Push Source. In GraphEdit I can successfully connect to a video renderer and see the video play. I have also managed to connect to AVI Mux and then file writer to write an uncompressed AVI file. The only issue with this is the huge file size. However, I have not been able to save the video in a compressed format. This problem also happens with the Ball and Push Source samples.

I can connect the output pin to a WM ASF Writer, but when I click play I get "This graph can't play. Unspecified error (Return code: 0x80004005)." I can't even figure out how to connect to the WMVideo9 Encoder DMO ("These filters cannot agree on a connection"). I could successfully save to mjpeg, but compression was not very substantial.

Please let me know if I'm doing something wrong in GraphEdit or if my source filter code needs to be modified. Alternatively, if there is another (non-DirectShow) option that would work for me I'm open to suggestions. Thanks.

Answer 1

You don't give details to help you with your modification of the filters, however Ball sample generates output which can be written to a file.

Your choice of WM ASF Writer filter is okay - it is a stock filter and it is more or less easy to deal with. There is however a caveat: you need to select video only profile on the filter first, and then connect video input. WM ASF Writer won't run with an unconnected input pin, and in default state it also has an audio input. Of course this can also be done programmatically.

The graph can be as simple as this, and it can be run and it generates a playable file.