Canon PowerShot G2 (PC1015) Reference Manual page 37

The following information may also appear with some image files.
Audio file is attached (wav file).
An audio file other than a wav file or a file with an unrecognized format is attached.
A JPEG file not supported by "Design rule for Camera File system" standards.
A file with an unrecognized format.
• Please note that image information recorded by this camera may not display
correctly on other cameras and image information recorded by other cameras may
not display correctly on this camera.
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Basic Functions