About HDV
HDV (High Definition Video) is a video format that allows you to record HD video in standard DV tape. Its compression scheme is called long-GOP MPEG2. HDV is an HD format created by a consortium of manufacturers including Sony, JVC, Canon, and Sharp. HDV allows you to record an hour of HD video on standard mini-DV videocassettes. You can connect an HDV camcorder to your computer via FireWire, so you can capture and output just as you would with a DV device.
It uses Long-GOP MPEG2 compression to achieve a maximum data rate of 25mps, which is the same as normal DV video. This standard yields extremely High Definition images in shorter space. The term long refers to the fact that P- and B-frames are used between I-frame intervals. At the other end of the spectrum, the opposite of long-GOP MPEG is I-frame-only MPEG, in which only I-frames are used. Formats such as IMX use I-frame-only MPEG, which reduces temporal artifacts and improves editing performance. However, I-frame-only formats have a significantly higher data rate because each frame must store enough data to be completely self-contained. Therefore, although the decoding demands on your computer are decreased, there is a greater demand for scratch disk speed and capacity.
1080-line HDV media uses an open GOP structure, which means that B-frames in the MPEG stream can be reliant on frames in adjacent GOPs. 720-line HDV media uses a closed GOP structure, which means that each GOP is self-contained and does not rely on frames outside the GOP.
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