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Editorial Team
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Asked: 2026-05-15T12:33:13+00:00

I am building an application that needs to read H264 and AC3 streams from

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I am building an application that needs to read H264 and AC3 streams from a MP4 container and mux them into a single ISMV file. The source MP4 file contains a number of video streams of different bitrates and a number of audio streams of different languages.

When I call IGraphBuilder::AddSourceFilter for my source file, I get a filter that has just two output pins: “Video” and “Audio”. How do I choose which particular stream (e.g.: which bitrate of a video stream) to use for “Video” and “Audio”?

Do I have to instantiate multiple source filters to read that file and mux them into ISMV, or am I missing something?

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  1. Editorial Team

    That depends on the demux you are using for MP4. I don’t think there is a stock MP4 demux, so you have probably got one as part of a decoder package, and that is acting as both source and demux.

    You can try the free open-source MP4 demux at http://www.gdcl.co.uk/mpeg4. You will need to AddSourceFilter (getting a file source with a single output) and then explicitly connect the source output to the demux input. Then you will have output pins corresponding to all enabled streams that the demux understands, and you can select the ones you want.

    G

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