QTIF (QuickTime Image Format) is a now-deprecated container format for still images from a QuickTime video. It consists of a description section and an image data section. The image data may be of various formats, including JPEG. The "native" parts of this format use big-endian byte order, though the image data part may use a different endianness depending on that format's standards.
.qif is the recommended file extension, though .qtif can also be found. The MacOS file type identifier is 'qtif'.
There's no simple way to reliably identify a QTIF file, but most of them have "
idat" or "
idsc" at offset 4.