Anatomy of a video file

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Resolution This is the number of pixels in each video frame. A frame is one of many still images you view in quick succession to get the illusion of motion. If you’ve ever riffled the pages of an animation flip-book, it’s the same concept, with each page representing a frame.

Video resolution is usually stated as the number of pixels horizontally by the number of pixels vertically. HD camcorders offer at least two resolutions: 1920-by-1080 (Full HD) and 1280-by-720. These are usually shortened to just their vertical measures, such as 1080 and 720.

Frame rate Continuing with the flip-book example, if you flip the pages slowly, you see a series of still images. But speed up the page-flipping, and those images start to run together in a fluid unbroken motion. The number of frames per second that you see is called the frame rate. For video, common frame rates are 30fps and 60fps. The faster the frame rate, the smoother fast-motion scenes will appear. When filming high-speed events like a NASCAR race or a football game, when given the same choice of scan method (interlaced or progressive, see below), choose the higher frame rate number. For example, if you have a choice between 1080/60i, 1080/30p, and 720/60p, choose 720/60p.

Scan method With scan method, you have two choices: interlaced and progressive. Progressive is the newer, better method, and it’s steadily pushing interlaced video out of the picture. Interlaced was developed in the 1920s to handle display limitations of the cathode-ray tube (CRT), that large glass monitor that made older television sets so heavy. Nimbler, solid-state flat-panel screens (LCDs or Liquid Crystal Displays) have largely replaced CRTs, letting progressive-scan video move to the fore.

Progressive scan video looks smoother and crisper than interlaced, with fewer artifacts. Two common camcorder video settings are 1080/60i (interlaced) and 720/60p (progressive). For shooting fast motion events, you’re usually better off filming in 720/60p, the progressive mode setting, even though the 720 resolution is half of the 1080 setting. The 720 setting gives you only 0.9 megapixels per frame compared with more than two megapixels for the 1080 resolution.

Until recently, if you wanted to shoot at the top available video quality, you had to choose between 1080/60i and 720/60p. Now we’re starting to see the best of both worlds. Last year the industry upgraded the AVCHD format to include 1080/60p, and some of this year’s new camcorders—such as the Panasonic HCs X900, V700, and V500 series models—offer it.

Bit rate The more you compress a video stream, the lower the bit rate, which speeds up file transfers and uses less memory. But lower bit rates yield lower video quality. For some video formats, such as AVCHD, your camcorder usually offers several bit rate levels, so you can choose your best trade-off between file size and video quality. For AVCHD, typical bit-rate levels include 24, 17- 13- and 9-megabits per second.

Camcorder shopping is easier than ever

Shopping for complex electronic equipment has never been a cakewalk. But if you're in the market for a new camcorder, your task will take a lot less effort than in the past. After a long transition away from standard definition (SD), mainstream high-definition (HD) camcorders are cheaper to buy and easier to work with.

We’re also seeing camcorder and computer makers, video software developers, and social network sites all syncing up more readily on standards. Video formats now consist of two main players: MPEG-4 and AVCHD. For video resolution, most casual shooters will be fine sticking with 1920-by-1080. For storage, SD memory is about the only game in town. Pretty much all camcorders use USB 2.0 and HDMI to let you pipe your video to your computer and TV.

Plus, it’s become much easier to quickly do what you want to do with your new camcorder. More than ever, you can shoot, edit, and post video in the same format, allowing an unbroken workflow from the time you capture that candid camera moment to when you toss it up onto YouTube. You already do that with your smartphone and pocket camcorder. It’s about time you can enjoy the same seamless operation with a traditional camcorder.

Bryan Hastings is a freelance writer in the San Francisco Bay Area.

This story, "Anatomy of a video file" was originally published by Macworld.

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