What is HDV?

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HDV - High definition video (DV)

HDV stands for "high definition video." It is a format that allows recording high-definition video on regular DV tapes. The format was pioneered by JVC (the wonderful company that released and later discontinued the absolutely fantastic DV 700 16:9 mini DV camera). Sony, Sharp and Canon supported the development of the HDV format.

The rationale underlying the HDV format was the provision of high-definition video production capabilities at low cost, with what are essentially high-definition camcorders. Don't forget that the only other options at the time if you wanted to shoot high definition were expensive cameras like the Sony F900.

There are two versions of HDV: 720p and 1080i. JVC cameras use the 720p format (720 lines at 30 frames per second, also called HDV1) whereas Canon and Sony use the 1080i format (1080 lines at 60 fields per second, HDV2).

As mentioned above, HDV involves recording a high-definition signal on regular DV tapes. For this reason, regular DV compression cannot be used. Instead, long-GOP MPEG-2 compression is used. This is similar to the compression used for DVD video.

The fundamental difference between regular DV impression and long-GOP MPEG-2 compression is that DV compression uses infra-frame compression, which basically means that every single frame includes all the data needed to interpret and display it. In other words, with regular DV compression, every frame is independent of others. In long-GOP MPEG-2 compression, on the other hand, compression has an inter-frame nature, which means that a certain amount of data is shared by several frames grouped together -- hence the name GOP, which stands for “group of pictures.” In this type of encoding, the correct interpretation of a frame may need data that is stored in neighboring frames. 1080i HDV uses a GOP length of 15 frames (if you know about MPEG-2 compression, this parameter will be familiar to you.)

Basically what this means is that editing HDV is not quite as computationally straightforward as editing regular DV, because in order to scrub the timeline frame by frame, the video editing program needs to take into account the fact that frames are not individually self-sufficient, as described above.

HDV audio is compressed by using the MPEG-1 layer II algorithm.

Examples of HDV cameras include Canon's XL H1, the Sony's HVR-V1U and JVC's GY-HD250U.