問79
頻出度★☆☆
映像データや音声データの圧縮方式はどれか。
平成25年度 春期 ITパスポート試験 問79
テクノロジ系情報メディア › マルチメディア技術
This question's explanation and your answers so far.
解説
問 79
Incorrectア
BMP (bitmap) is the standard still-image format on Windows, and it basically stores the color information of each pixel just as it is, without compression. It handles neither video nor audio, and it cannot even be called a compression method, so it is wrong.
Incorrectイ
GIF is a still-image format supporting up to 256 colors, and it uses lossless compression. Animated GIFs that switch between several frames do exist, but GIF cannot handle audio and is not a compression method for video and audio, so it is wrong.
Incorrectウ
JPEG is a lossy compression method for full-color still images such as photographs. It is indeed a compression method, but its target is a single still image; video (moving images) and audio are outside its scope, so it is wrong.
- エ
正解 The correct answer is エ, MPEG. MPEG (Moving Picture Experts Group) is a family of compression standards for video (moving images) and audio, including MPEG-2, used for DVDs and digital broadcasting, and MPEG-4, aimed at network delivery and mobile devices. By combining “inter-frame compression”, which records only the parts that change between successive frames, with lossy compression that discards information people are unlikely to notice, it can greatly shrink video and audio, which carry large amounts of data. MPEG-1 Audio Layer-3, the audio part taken out on its own, is what is commonly called MP3. Among the choices, MPEG is the only compression method that handles both video data and audio data, so エ is correct.
ここがポイント
- MPEG is a compression method for video (moving images) and audio. MPEG-2 is used for DVDs and digital broadcasting, MPEG-4 targets network delivery and mobile devices, and MP3 corresponds to the audio part of MPEG-1.
- Sorting out the still-image formats: BMP is uncompressed, GIF is 256 colors with lossless compression, PNG is full color with lossless compression, and JPEG is full color with lossy compression. Memorize them in contrast with “video and audio means MPEG”.
用語