关于DC镜像格式：CDI、GDI、bin+cue、chd

klaus

使用 Dreamcast 模拟器时会遇到 CDI、GDI、bin+cue、chd 格式镜像，该选哪一个呢？

粘贴一段主流DC模拟器 Flycast 的使用说明：

CDI: They are cut-down images of the game originally made to be burned on a CD to save space, hence the name CD-I. Some CDI images have cut content, audio compressed and lowered in quality, FMVs cut/compressed to look even worse then they already do on large modern televisions, online or other content cut and removed, and these are just some ways we get the size down. DO NOT USE UNLESS YOUR SUPER LIMITED ON SPACE, OR BURNING TO A CD AND THE GDI VERSION IS OVER 700 MB. ONLY USE FOR CUSTOMIZED ROMS OR HOMEBREW GAMES.

GDI: This is a dump of the original GD-Rom. The size is always noticeably bigger than the CDI image format, with no cut content or anything changed. For many, GDI is the go-to for anything Dreamcast emulation related. Its only downside, is it is the largest a rom can be. large collections can be zipped to keep size down, BUT, you must unzip before playing.

CHD: This is the way to go with flycast as your emulator. Just another reason Flycast is a good choice, it supports the little supported, but highly sought, CHD format. See, Remember, we do NOT want CDI for most cases, unless we are buyrning to a CD, or your are VERY limited on space, due to the fact it has files missing, compressed audio, compressed FMV's, and more ways are used to reduce the size, where CHD, is a GDI, in teh sense it is a full rip, un touched, but CHD, is a form of compression, that few emulators can decode on teh fly. So you will get the same quality as your regular GDI version, but your CDH will be smaller with NO loss in quality/content.

CDI：简单说是一种有损压缩格式，主要压缩图片、视频和音频。优点为占用空间较小，缺点是有损压缩可能影响游戏体验。

左边为 cdi 格式截图，右侧为 chd 格式截图，通过对比看出 cdi 游戏视频码率较低：

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GDI：原始GD-rom转储，可以简单理解成1：1拷贝，很明显这类镜像没有经过压缩，存储空间较大。

bin+cue 格式在 Redump Sega Dreamcast 收集中很常见，有很多分轨文件，包含光盘中无用且仅用于填充的数据，这也是1：1拷贝，存储空间与gdi相当。

CHD：如果经常鼓捣mame，会接触到该格式，可以简单理解成无损压缩，存储空间比cdi还低，但图形视频音频质量与gdi一致。

每种格式都有优缺点和特殊用途，根据需求选择即可。