Sony DCR-TRV Operating Instructions Manual page 50

Using the wide mode
ID-1 system
The ID-1 system sends aspect ratio (screen horizontal/vertical ratio) information (16:9,
4:3, or letter box) with video signals.
ID-2 system
The ID-2 system sends a copyright protection signal with ID-1 signals inserted
between video signals when you connect your camcorder to other equipment using the
A/V connecting cable.
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