HDV stands for High-Definition Video. It should not be confused with HD video. HDV is the high-definition version as applied to the DV magnetic tape format. One of its selling points is HD video can be recorded on an inexpensive DV cassette tape.

HDV is a video format developed jointly by JVC, Sharp Canon, and Sony and was announced on September 30, 2003 in Japan.
Companies that expressed support for the format included :
- Adobe Systems Incorporated
- Canopus Co., Ltd.
- KDDI R&D Laboratories
- Sony Pictures Digital Networks
- Ulead Systems, Inc.
HDV Encoding
HDV is encoded in MPEG-2 (MP@H14 for video) and is recorded on a mini-DV tape or a standard DV tape. The aspect ratio supported is 16:9. Video resolution is available in 1080i and 720p.
Although it is recorded in higher quality, you get the same tape run time. This is because the video bitrate is set at that of DV. As such, you can capture HDV through a Firewire connection into a video editor.
HDV was meant as a replacement for DV. It allowed amateurs and pros to shoot video at a higher quality affordably using the same mini-DV tape. Recording, as mentioned earlier, can also be done on a standard DV tape.
That said, there are differences in the HDV format
Different Types of HDV
There are three HDV formats, each manufacturer has its own standard.
HDV 720p
JVC’s version of the format is called HDV1. Video is recorded at a data rate of 19Mbps. Resolution is 720p (1280 x 720), namely 720/60p, 720/30p,
720/50p and 720/25p
There’s an option to record at 720/24p.
HDV 1080i
Sony’s HDV format is called HDV2. So, is Canon’s. Video is recorded at a bit rate of 25Mbps. Resolution is 1920 x 1080 in interlaced mode (1080i) -1080i/60, 1080i/50.
There’s an option to record at 1080/30p, 1080/25p and 1080/24p
Color Sampling
Color sampling for both HDV 720p and HDV1080i is set at 4:2:0.
HDV 720p and HDV 1080i Audio
For audio compression MPEG1 Audio Layer II is used. Sampling Frequency is set at 48kHz.
Quantization is at 16 bits. Bit rate after compression is 384kbps.
Audio Mode is Stereo (2 channels) .
For HDV 720p there’s an option to record with MPEG1 Audio Layer II 2 channels and in PCM (2 channels or 4 channels) simultaneousy.
For HDV 1080i there’s an option to record in MPEG2 Audio Layer II or MP2 (4 channels).
Limitations and Incompatibility
You can’t play a JVC HDV tape or transfer through FIrewire on a Sony HDV deck or video camera. Similarly, JVC HDV will not support a Sony HDV tape.
Canon, won’t play JVC and Sony HDV tapes.
Video Editing
If you’re editing on Premiere Pro, for instance, and are capturing video into the program, you’ll be asked whether you are capturing DV or HDV.
You have to select one of these modes for the Firewire capture device to understand the type of video format it will be handling – DV or HDV?
HDV vs DV : Difference Between HDV and DV
Here are the main differences between HDV and DV
Compression Method
With DV compression is in the intraframe mode. Each frame is compressed independently of the other frames.
HDV uses MPEG-2 compression. With MPEG-2 intraframe and interframe compression is possible.
Interframe compression is undertaken within a Group of Pictures (GOP). Basically, the compression of a frame is dependent on the frame that comes before it. Repeated information (if there’s no change in movement) is discarded.
The disadvantage of the MPEG-2 compression is a single dropped frame affects the GOP. Experts recommend the use of DV tapes made specially for the HDV format.
Also, an hour of DV footage consumes around 13GB of hard disk space. HDV (native format) takes up around 11GB.
The MPEG-2 compression offers quality video but it requires a more powerful video editing computer.
Resolution
HDV is a high-definition tape format that offers 1080i resolution at 30 frames per second NTSC and 25 frames per second for PAL. This is just one of the resolutions available. DV on the other hand offers a standard definition resolution of 480i at 60 frames per second.
In other words, HDV 1080i offers at least 4 times the image area of standard definition DV.
HDV Camcorders
JVC released the first HDV camcorder (handheld) GR-HD1 in 2003. Sony’s first HDV camcorder was the HDR-FX1 (1080i) released in September 2004. Canon’s Canon XL H1 made its debut in September 2005.
By 2010 production of HDV camcorders had ceased.
Still, you may find used models online though.

Sony HVR-Z5P Professional HDV PAL Camcorder.
HDV Portable Video Recorder

The Sony GVHD700 is used to review HDV tapes after shooting.
HDV Tapes
Tapes specially made for HDV shooting are available online. These tapes will help you avoid incidences of dopped frames.

Check out the following:
PHDVM-63DM DigitalMaster DV/HDV/DVCAM Tape.
References
HDV: What You NEED to Know! The Complete Guide
How to Shoot, Edit and Distribute HDV: The Complete, up to Date Guide to Working with the HDV Format