Mp3与标记
做的比较精致的Mp3可以看到作曲家的名字选自哪张专辑。这些都源自于ID3标记的作用。什么是ID3标记呢，请看。翻译的不准确的地方参见下面的原文
标记简史
过去
很久以前，有这样的一些大公司，带着为实现4声道而奋斗的记忆犹新的失败，组织了一个专家小组, 目标是开发未来的声音压缩技术。幸运的是，他们做到了。一种名叫MP3的格式（ MPEG Layer 3的缩写）, 利用了我们耳朵听觉上的欺骗性，牺牲了一些不管怎样我们都不会听到的频率. 同时，他们通过把声音用小的独立的压缩包的来表示声音数据格式这个方式来实现流式点播。每个包有一个包头包括一些解压缩的相关信息。 包头最后用一些或者多个字节来结束，他们用它来添加一些附加信息，诸如一个“版权”字节或者一个“私有”字节。
因为Mp3这个格式具有如此出众的压缩率并且仍能保持很好的声音质量（我们都知道声压缩率越高，声音质量往往越差），他很快被视为数字音乐的真正标准。缺乏在文件中包含文本信息的能力是一直让人头疼的。突然，一些人 (Eric Kemp alias NamkraD, 就如我以前说过的) 有了一种设想，用一种标签(tag),使用固定大小的128-byte,存放在声音文件的最后。他会包含，标题，艺术家，专辑名，曲风，注释等字段（title, artist, album, year, genre and a comment field）. 一些人，（很有可能就是前面说到的那些）实现了这一设想，让所有的人感到高兴。之后很快， Michael Mutschler,MP3ext的作者,扩展了这个标签， 命名为ID3，同样包含了这个音乐来自CD的第几个track的信息。他使用“评论“comment字段的最后两个字节实现这个功能。并将此名为他的变体ID3 v1.1.
现在
但是 ID3 v1.1 标签人仍然有着许多明显的限制和缺陷。他只支持很少的一些字段信息, 并且这些字段限制在30字符的长度，这样一来就不可能正确表述诸如"The Hitchhiker's Guide to the Galaxy from BBC Radio" 或者 "P.I. Tchaikovsky's Nutcracker Suite Op. 71 a, Ouverture miniature danses caract閞istiques by The New Philharmonic Orchestra, London, conducted by Laurence Siegel". 因为ID3 v1.1标签的位置是声音文件的末尾，在声音流式传送的时候他也是最后到达的。固定的128 bytes也无法更好的扩展. 那就是为什么我(Martin Nilsson)和一些同伴认为新的ID3标签会更加适合的原因.
新的ID3标签命名为ID3v2并且现在是一个非正式的标准。也就是说，我们决定，因为这个标准只有少之又少的改进和增加，不足以把这个草稿定为标准。 (没有标准化的组织来支持这个标准). 你可以在此找到非正式的标准. ID3v2 经常跟着修订版本号，例如当前的非正式标准为ID3v2.4.0.
The short history of tagging
The past
Once upon a time, there were some giant companies that, with the failure of the 4-channel battle fresh in mind, formed an expert group with the mission to invent tomorrow's technology in sound compression. Fortunately, they did. The format, named MPEG Layer 3 or for short MP3, took advantage of the fact that our ears are not nearly as good as we generally believe them to be, and thus omitting frequencies that we wouldn't hear anyway. They also made the format suitable for streaming by letting the sound be represented in small, individually compressed blocks of audio data. Each block had a header containing some information relevant to the decoding process. As they ended up with a few bits to much, they used them for some additional information such as a 'copyright' bit and a 'private' bit.
Since the format had such an outstanding compression and still very good sound quality, it was soon adapted as the de facto standard for digital music. The lack of possibilities to include textual information in the files was however disturbingly present. Suddenly, someone (Eric Kemp alias NamkraD, I've been told) had a vision of a fix-sized 128-byte tag that would reside at the end of the audio file. It would include title, artist, album, year, genre and a comment field. Someone, possibly the very same someone, implemented this and everyone was happy. Soon afterwards, Michael Mutschler, the author of MP3ext, extended this tag, called ID3, to also include which track on the CD the music originated from. He used the last two bytes of the comment field for this and named his variant ID3 v1.1. (more information about ID3 and ID3v1.1 can be found here)
The present
The ID3 v1.1 tag still had some obvious limitations and drawbacks, though. It supported only a few fields of information, and those were limited to 30 characters, making it impossible to correctly describe "The Hitchhiker's Guide to the Galaxy from BBC Radio" as well as "P.I. Tchaikovsky's Nutcracker Suite Op. 71 a, Ouverture miniature danses caract閞istiques by The New Philharmonic Orchestra, London, conducted by Laurence Siegel". Since the position of the ID3 v1.1 tag is at the end of the audio file it will also be the last thing to arrive when the file is being streamed. The fix size of 128 bytes also makes it impossible to extend further. That's why I (Martin Nilsson) and several along with me thought that a new ID3 tag would be appropriate.
The new ID3 tag is named ID3v2 and is currently in a state of 'informal standard'. That is, we decided, since there were less and less improvements and additions made, to proclaim the draft as a standard (an informal one since no standardization body has approved this decision). You can find the informal standard here. ID3v2 is often followed by its revision number, i.e. the current informal standard is ID3v2.4.0.
ID Tag 3 v1 &1.1
www.id3.org/id3v1.htmlID Tag 3 v2 4.0
www.id3.org/develop.html 歌词的标准
www.id3.org/lyrics3.html
