QuickTime Streaming

Media Preflight

Once QuickTime has selected and opened a packetizer component, it will call the packetizer's RTPMPPreflightMedia function to verify that the packetizer can handle the specific media and sample description. A packetizer can reject media as a result of this call, even if the media fits the profile described in the packetizer's public resource.

For example, the 'pcki' resource for the Qualcomm PureVoice audio packetizer indicates support for audio media and PureVoice compression, but the packetizer only supports 8 kHz sample rates over RTP. The RTPMPPreflightMedia call to this packetizer returns noErr for 8 kHz audio, and an error for any other sample rate.

The media preflight function is defined as follows:



 
pascal ComponentResult RTPMPPreflightMedia(RTPMediaPacketizer rtpm,

                OSType inMediaType, 

                SampleDescriptionHandle inSampleDescription);

This call is made to make sure your packetizer can handle a given media type and sample description. Return noErr if you can support it. Return qtsUnsupportedFeatureErr if you cannot.