We now live in a high-definition society. Most TVs are HD, Blu-Ray grows every month, and HD cable and satellite is a given. Back in 2003, when HD was in its infancy, a consortium of electronics manufacturers began working on a high-definition tape that would replace Mini DV. The idea was to create a new video format that would enable high-definition video to be stored on the regular Mini DV tapes that many consumers already had. They called it High Definition Video, or HDV.
Today, the idea seems quaint, since almost every camcorder is high-def, and tapeless to boot. But HDV provided excellent video quality, and we often see HDV tapes at Timeless DVD since many consumers took to the format. So if you’ve ever wondered what HDV was all about…read on.
How does HDV work?
HDV creates high-definition video in the widescreen, 16:9 aspect ratio. It can write directly to plain old Mini DV and DV tapes, and supports both 720p and 1080i definition. Like DVD, the format uses MPEG-2 compression and achieves the same bitrates of regular DV (25Mbps). Audio is written to MP3 and only compressed to 75%.
The downside of HDV
Unlike traditional DV encoding, HDV encodes to MPEG-2 (actually a format called MPEG-2-TS). MPEG-2 is the same format that is used on DVD discs, and so HDV is subject to the same compression issues.
The drawbacks of MPEG-2 technology can be best understood via a crash-course on “GOP,” which is an acronym for “Group of Pictures.” In American (NTSC) video, 29.97 frames occur during every second of video. In DV video, each frame carries complete data information, which is why DV video is so high-quality and takes up a significant amount of hard drive space.
MPEG-2 video, on the other hand, has been compressed so that only a few frames carry complete picture information. The other frames are space-saving, downgraded images of the real video picture. These downgraded frames aren’t noticeable when watching a DVD, but quickly become apparent during editing.
A typical GOP:
Each square in the diagram represents a frame of video. The I frames contain complete picture data and only occur a few times during each second of video. P frames are the second-most prevalent and “predict” what the video should look like based on the I frames. B frames are the most numerous and calculate data from both the full I frames and reduced P frames.
What this all means is that frame-accurate, high-quality editing is impossible with MPEG-2 video. It’s the reason why we tell customers over and over again: NO, it’s not a good idea to edit the video that’s on your DVD. So while HDV is a great video format and definitely useful for HD recording, its use of MPEG-2 encoding is its primary drawback–at least where editing is concerned.
One last note: If you do have HDV tapes and want to watch your video on regular DVD discs, Timeless DVD can accommodate you. We have decks that can downgrade the HD signal to regular standard-def video, and the results are actually pretty fantastic.
