Videonics Firestore Instruction Manual page 52

PAGE 46 VIDEONICS FIRESTORE
FireStore File Formats (cont)
FireStore also records DV clips to your FireWire disk drive in what we refer
to as an "edit-ready" file format. This allows you to use recorded clips in-
stantly in most DV based edit systems. Files are recorded in one of four dif-
ferent formats. These are RawDV (.dv), AVI Type 1, AVI Type 2 or AVI Type
2 Canopus. Follows is a brief description of these file types.
Raw DV (.dv) File Format
During playback aDV video camera sends 'raw DV' out over the Fir eWire
connection to whatever device is listening on that FireWire path. Each frame
of DV data (exactly 120,000 bytes for NTSC) is self contained. It contains a
single frame of video, and contains 1/30 (1/25 in PAL) second worth of
audio data. The format is strictly defined and agreed upon by all major
manufacturers. The format describes where the information goes, and is
designed to withstand some loss of data during transit without becoming
totally unusable. It also includes timecode information for each frame, and
some auxiliary data about the recording.
A raw DV file captured on a hard drive, then, is a file that contains exactly
the same bytes that came in through the FireWire plug. That exact same file
can be sent out the FireWire plug back to the camera or VCR for playback.
Needless to say a raw DV file is the simplest and most ef ficient method for
storing DV data on a hard drive.
T ypically, this sort of file has a '.dv' file type extension.
AVI Type 2 File Format
AVI was developed by Microsoft and in many ways is similar to QuickTime.
It is also a wrapper for an assortment of time based media. The technology
has morphed from the old Video For Windows tools into the newer
DirectShow and NetShow toolsets.
The format AVI-DV-Type2 specifies how a raw DV data stream should be
stored in a file. Like the QuickTime specification for the storage of DV, each
DV frame has (120,000) bytes is stored in the file. Also, the audio data in each
frame is identified and copied to another place in the file. The AVI format
includes data at the start and end of a file that provides an index into that
file. The index points to every video frame and audio chunk in the file.
The Interleaved in AVI refers to the spacing and/or duration of the video
and audio chunks in the file. FireStore writes 16 intact 'raw DV' frames into
the file, then writes an audio chunk that contains the audio from those same
16 frames. 16 more DV frames are written, then another 16 frames worth of
audio, etc.