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The formats: HDV (High Definition Video) and AVCHD (Advanced Video Codec High Definition)

There are two distinct formats for consumer level high definition camcorders: HDV (High Definition Video) and AVCHD (Advanced Video Codec High Definition).

HDV

HDV uses the DVD-like MPEG2 compression to squeeze high definition video onto MiniDV tape used in standard definition camcorders, along with compressed stereo sound.

HDV, however, captures a picture that has a resolution of 1440 x 1080, which is a bit short of the 1920 x 1080 resolution that is the real-deal high definition (not that this stops one camera company from calling their HDV 'True-HD', even though the video signal has only 1440 picture elements). This is because to record full resolution 1920 x 1080 on Mini DV tape would exceed the mini DV tape's capabilities. To get around this, the 1080i HDV format uses rectangular pixels, rather than uniformly square ones, that when replayed, fill a standard
1920 x 1080 frame.

This doesn't make HDV inferior; in fact it's in good company. The broadcast formats XDCAM HD, DVCPRO HD and HDCAM all have the same or lower resolution as HDV.

There are two main problems with HDV, though. First, tapes wear out. The magnetic material eventually wears away under repeated playing and recording. When the wear becomes significant, your video is gone. Second, getting to the place that you want is slow with tape. It has to be wound forwards and backwards, just like the VCR tape of old.
On the up side, HDV has the advantage of wide support in computer software for editing, and the tapes themselves are cheap, and each can fit 60 minutes of high definition recording.

AVCHD

AVCHD is the relative newcomer and has some pluses and minuses. Based on the MPEG4 AVC/H.264 standard, the format is compressed in a similar approach to that used on the Blu-ray and HD DVD disc formats. It brings with it the advantage of up to eight channels (7.1) of surround sound but takes up less space than HDV.

These camcorders can use 8cm recordable DVDs, hard disk drives, or even memory cards as their recording media. The system is very flexible, so you can select a trade-off between the amount of video you want to capture and the quality you are after.

At the high-quality settings, about 20 minutes of video recording can be captured on an 8 cm DVD. The main advantage of this is that you can drop the resulting DVD into a Blu-ray player and immediately enjoy your high definition video on the screen.

Those AVCHD camcorders that use memory cards for recording are packaged with a new version of the Secure Digital memory card, called SDHC (for Secure Digital High Capacity). These currently have a capacity of 4GB or almost the size of a regular 12 cm recordable DVD, so at the higher quality settings over an hour of recording to one card is possible.

These provide fast access to a chosen part of your recording, low power requirements, good proof against shock, and the possibility of carrying plenty of recording media with you. While they presently cost around $150 each, expect the prices of the cards to fall sharply, and their capacities to increase further (16GB is just around the corner).
Hard disk-based AVCHD camcorders can fit a lot more video on them, but you have to delete, or download the video onto a computer, to make more room eventually.

A big advantage of hard drive, disc and memory card storage is random access; no need to spool through kilometres of tape. Another is that AVCHD records in the full high definition resolution: 1920 x 1080.

Regarding quality, I have shot and viewed the results from both formats with different camcorders. The results are amazing: well-shot high definition footage is equal to the best of normal programming.

Some people have reported that AVCHD camcorders were a peg or two lower than HDV units - I suspect some models use a higher compression level, getting more on the hard drive/memory card but dropping in quality.

Back Page 4 of 9  Next - High definition = more room needed for storage  

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In this article

• High definition camcorder buyers guide
• Standard definition vs high definition
• Steady shooting with image stabilisation
• The formats: HDV (High Definition Video) and AVCHD (Advanced Video Codec High Definition)
• High definition = more room needed for storage
• What accessories and software do you need?
• Viewing and keeping home video
• Pros and cons of going HD; Purchase checklist
• Using a videocamera

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