The two applications which drive many aspects of personal computing are video and games - and they are obviously closely related. With the availability of inexpensive capture devices such as IOmega's Buz, many are jumping into video and becoming frustrated in the process. This note is intended to address the beginning user of digital video.
Like audio, most video begins with an analogue signal. If your camera generates a digital signal directly, most of this page does not apply. For the rest of us, some capture device is required which converts the analogue information to digital as your sound card does with audio. In general, the capture is to a lightly compressed format. (Without compression, you would have to record at around 30 MB/sec. That would both load your system very heavily and rapidly use up all available space on a hard drive.) The lightly compressed format is usually compressed further offline with a codec (encoder/decoder) that limits the quality of the resulting file. One popular format is whitebook MPEG, which is used to generate VCD. In that form, the data rate is about 1x in CD-ROM terms, meaning that the signal has been compressed 200:1. In that format, a CD-R can hold about an hour of video. At 50:1 compression, a CD-ROM can hold only about 15 minutes of video. Obviously, the more compression used, the lower the resulting quality of both video and audio.
In order to play back a video, the playing computer must have the same codec installed as was used to create it. Many such are available and whenever you install one to encode, you will be able to play it back. However, the person to whom you send it may not have that codec - and in that case will need to find it and to install it before she can watch your product. Intel has several Indeo codecs and there are many others with modest advantages from one to the next. Those codecs usually generate AVI files on a PC (MOV is more common on Mac). AVI and MOV are different envelopes wrapped around the same raw data stream - as WAV and AU are envelopes for audio data. Because of the variation in AVI codecs, it may be most convenient to compress your video to MPEG, which is consistent across platforms and has a standard codec. You can produce MPEG with other products, but many find the Xing encoder most convenient and reasonably priced.
A key factor is the size of the file you generate. Since your original recording will be an AVI even if you are going to compress it to MPEG, you are limited by the specification of AVI. The definition of that format limits it to 2.1 GB total size. While that seems immense, in video terms it is quite limiting. If your original capture is compressed 50:1 (which is very high), an individual capture must be less than 45 minutes. Compression to MPEG is similar to compression to MP3 in audio - and similarly makes editing in that format almost impossible. In order to edit your video, you will need to operate with an AVI and use a tool such as Adobe Premiere or ULead MediaStudio. Editing is very demanding on your system, so be prepared to add large, fast HD's, plenty of RAM and powerful processors if you want to deal with ten minutes' worth at one time. However, it is important to recognize that a high-performance capture card is of little value for home video. If you have a very high quality digital signal, you may throw away 90% of it in compression. If you start with a half-frame source, you will 'only' throw away 60%. The results will be indistinguishable. (Obviously, the rules and the systems are very different for broadcast quality.)
No one can tell you what picture quality is good enough for your purposes. But once you know what you want, do not overbuy to achieve it. High quality in capture means major system revision; modest quality will let you know how much you are willing to invest and give you satisfying results.
E-mail me at cdrecording@mrichter.com
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