Serial Data Transport Interface is a way of transmitting data packets over a Serial Digital Interface datastream. This means that standard SDI infrastructure can be used.
Developed to address the needs of the growing number of compressed video standards (DV, DVCPRO, BetaSX, MPEG2) it allows lossless transfer of data to other devices which have the same codec, for example DV to DV or SX to SX.
DV is a format for storing digital video.
Betacam is a family of half-inch professional videocassette products developed by Sony in 1982. In colloquial use, "Betacam" singly is often used to refer to a Betacam camcorder, a Betacam tape, a Betacam video recorder or the format itself.
Using a standard SDI transport, the extra data is placed within normal active video, between Start of Active Video (SAV), and End of Active Video (EAV). This gives 1440 10bit words of data at 270Mbit/s (1920 words in the 8bit 360Mbit/s standard).
If an SDTI stream is viewed using a standard SDI device, then the raw data can be seen as a small strip along the left hand side (usually in purple). The DVCAM SDTI has video data at the top, control data in the middle (Timecode, etc.) and audio at the bottom just like it is organised on the tape.
A timecode is a sequence of numeric codes generated at regular intervals by a timing synchronization system. Timecode is used in video production, show control and other application which require temporal coordination or logging of recording or actions.
Because SDTI is used for compressed data the area used is less than a full screen; this allows for faster than realtime transfers.
SDTI is standardized as SMPTE 305M. A 1.5 GBit/s version, using the high definition serial digital interface, is standardized as SMPTE 348M.
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