QuickTime Streaming

Hint Track Format

You prepare a QuickTime movie for RTP streaming by adding hint tracks. Hint tracks allow an RTP server to stream QuickTime movies without requiring the RTP server to understand QuickTime media types, codecs, or packing. The RTP server needs to understand the QuickTime file format sufficiently to find tracks and media samples in a QuickTime movie, however.

Each track in a QuickTime movie is sent as a separate RTP stream, and the recipe for packetizing each stream is contained in a corresponding hint track. Each sample in a hint track tells the RTP server how to packetize a specific amount of media data. The hint track sample contains any data needed to build a packet header of the correct type, and also contains a pointer to the block of media data that belongs in the packet.

There is at least one hint track for each media track to be streamed. It is possible to create multiple hint tracks for a given track's media, optimized for streaming the same media over networks with different packet sizes, for example. The hinter included in this release of QuickTime creates one hint track for each track to be streamed.

Hint tracks are structured in the same way as other QuickTime movie tracks. Standard QuickTime data structures, such as track references, are used to point to data. In order to serve a QuickTime movie, your RTP server must locate the hint tracks contained in the movie and parse them to find the packet data they point to. You should review the QuickTime File Format documentation before you read the remainder of this hint track information. You will also find it helpful to refer to the QuickTime File Format periodically in the course of reading this document.

Hint Track Format

Locating Hint Tracks in a QuickTime Movie

Finding the Hinted Track from a Hint Track

Finding a Hint Track from a Hinted Track

Hint Track Structure

Media Atom

The Hint Track User Data Atom (`'udta'`)

Hint Track Samples

Hint Track Information Atom (`'hnti'`) in Movie User Data Atom