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Help with video terminology
Posted : Wednesday, July 15, 2009 7:23:01 AM(UTC)
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What are "compressors" and "bitrates"? How can I decide what settings to use when ripping my DVDs?
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Posted : Wednesday, July 15, 2009 7:25:02 AM(UTC)
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A "Compressor" is a method of reducing the size of a video or audio file, by mathematically changing the data according to a set of rules. Using a compressor can reduce the size of a file by up to 95%. Generally, the higher the compression level, the smaller the file, and also the lower the quality when the file is played back. Some of the more commonly-seen video compressors are MPEG 2, MPEG 4, and Windows Media Video. Common audio compressors include MP3 (MPEG 1 Layer 3), AAC (Advanced Audio Codec), and Windows Media Audio.

A "bitrate" measures how much information is used to describe a video or audio stream per second. The more bits that are available, the more accurate the reproduction of video and audio can be. Higher bit rates also mean larger files. In video, a DVD uses 5,000-7000 Kbps (Kilobits per second). HDTV can use up to 15,000 Kbps.

Note that with compression, lower bitrates can give good quality. To most people, an MP3 file at 320 Kbps sounds as good as a music CD at 1400 Kbps. One advantage of newer, more advanced compressors like the Advanced Audio Codec (AAC) is that they can give acceptable quality at low bitrates. An AAC file at 128Kbps can sound as good as an MP3 file at 256 Kbps. This lets an AAC file be smaller than an MP3 file while giving the same audio quality.

For more information on video and audio files, read our free eBook here.
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