QuickTime Streaming

Writing a Media Packetizer

A media packetizer takes media data and determines how to packetize it for transmission over RTP. A packetizer can be specific to a particular media type and compression format, such as a packetizer for Sorenson video, or it can be more generalized, such as a packetizer for any uncompressed audio, or even a packetizer for any QuickTime media.

QuickTime Streaming calls a media packetizer during the course of hinting a movie or during live transmission. The packetizer is passed sample data, which it breaks into packets and passes to a packet builder. The packet builder may then transmit the packets over RTP or use them to create a hint track. The media data is presented to the packetizer in the same format for a live transmission or for hinting, and the packetizer produces the same output in both cases.

The packetizer component must implement several functions, and must also provide a public component resource that describes the type of media, compression, and track characteristics that the packetizer supports. This resource also provides information on the packetizer's relative speed and the format's ability to handle loss.

This section describes

the sequence of events your packetizer should expect
the packetizer component type and subtype
the 'pcki' public resource
media preflight
initialization
set up and information functions
sample processing functions
flush and reset functions

Function definitions and additional discussion of all media packetizer functions can be found in the Media Packetizer Functions section.

Writing a Media Packetizer

Sequence of Events

Packetizer Component Type and Subtype

The 'pcki' Public Resource

Media Preflight

Initialization

Set Up and Information Functions

Sample Processing Functions

Calling the Packet Builder

Flush and Reset Routines