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Codec Private Data missing


I’m trying to stream a VOD encapsulated in mp4 format. When a iOS client requests the video (call it video1), it plays perfectly. However, when a silverlight player requests it, it can’t be played. Using the same silverlight player, i try to reproduce another mp4 file (call it video2) and it works like a charm.

So, i captured some packets when the player requests both of them, and i found something odd. The only difference i could find between each VOD manifest WMS sends, is that in the case of video1, the video ‘QualityLevel’ tag has no ‘CodecPrivateData’, i.e., the field exists but it’s empty!. Now, according to the IIS Smooth Streaming specification (, that field is mandatory and it’s quite clear what it should contain (SPS and PPS info).

I suppose this field is filled by Wowza when creating the manifest by parsing the data from the mp4 file. I believe the mp4 file contains such information…

Any clues?

Thanks in advance!,


Do whatever you did to create video2, is all I can suggest. What works.