Media Foundation Source or H264 / AC3 differences between Windows and Phone 8?

Question

I've got a working Matroska (MKV) Media Foundation Source for a Windows Store app (PC x86). It will play several different matroska files that contain H264 encoded video and AC3-encoded audio.  It even has seek support.  I've written the app
as a HTML/typescript Universal app with the MF Source as a C++ dll. 
The problem is that the same code will not work on Windows Phone 8.  I can play videos that don't require the external MF Source (i.e. MP4 files and AVI files) just fine on both platforms through my app, but the same MKV videos that played on an x86
PC will not play on Windows Phone 8 (Lumia 920).
I looked at the specs for the Snapdragon processor and it should be able to support both H264 at 720p resolution and AC3 (2-channel only).  So I don't know what else I need to do to get this to work on WP8.  The audio I'm trying to play is actually
6-channel, so that made me wonder if it was failing because WP8 supports 2-channel max, but I would have thought the audio just wouldn't work and the video would play normally.
Does anyone have any suggestions?
*edit* - just to be more specific, I can parse the file and create the presentation descriptor without errors.  But when I finish opening the file and call the event for that, nothing else happens.  What is weird is that the javascript video player
never throws the "canplay" event, nor does it throw the "error" event.
Lee McPherson

Answer 1

Thanks, not a bad suggestion to try. 
On my Windows machine, I tried to get the MediaEncodingProfile via the createFromFileAsyc method.  With a known file type, it outputs all properties of the video and audio streams (bitrate, etc).  With an MKV file (container file with H264 video
and AC3 audio), I only get the type and subtype properties. Everything else is zero or null.  This is because in my MFSource, I only set the type and subtype.  This still allows the video to play on my windows machine.  I assume the
built-in MFTransform for H264 video-to-uncompressed video parses the stream to get the relevant information.  Likewise for audio.
On Windows Phone, when querying the file's MediaEncodingProfile, I get the same result. This is telling me that my MFSource will parse the file properly and set the subtypes for video and audio correctly.  Everything else is still null or zero. 
However, the file does not play.  There is no returned event to the video element that it even *can* play.
Perhaps, I need to fill in the video and audio stream properties on the Windows Phone version.  I really don't want to because that would mean having to parse some of the underlying video and audio streams themselves, not just parsing the container
information.  (More work!)  But this is what I mean when I ask about the differences between Windows and Windows Phone... perhaps the WP8.1 & Windows MFTransforms are different? 
*EDIT* - I do get a JavaScript Console error that I didn't notice before: AUDIO/VIDEO: unknown MIME type.  (VS error code: MEDIA12899)
Lee McPherson