blocks|key|1850857|text|Mp3是有损的，但它以一种非常特殊的方式有损。根据设计使用的算法，用于丢弃您的耳朵无法听到(或非常难以听到)的音频的某些部分。一遍又一遍地在相同的压缩级别上重复压缩过程可能会对给定的一段音频产生几乎相同的结果。然而，一些额外的损失可能会慢慢累积。如果你要经常修改文件，这可能不是一个好主意。如果你关心质量，这也不是一个好主意，但是如果你关心质量，那么使用MP3总的来说是个坏主意。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1850858|您可以使用编码器和解码器构建一个测试，对几个不同的mp3文件重新编码几次，并观察它们是如何变化的，这可以帮助您确定恶化的速度，并确定您是否可以接受它。听起来你已经有了可以用来运行这个简单测试的库了。|1850859|MP3文件是由音频的“帧”组成的，因此，通过一些努力，应该可以通过最小的处理来删除整个帧(删除帧，更新文件头中的一些次要细节)。我相信帧是相当短的(每个帧几毫秒)，这会给出你想要的精度。因此，在MP3+File+Format上进行一些阅读应该会为您提供足够的信息来编写您自己的python库来实现这一点。这与传统的“音频处理”有很大的不同(因为你不关心精确度)，所以你不太可能找到一个现有的库来做这件事。正如你已经发现的，大多数都会先解压缩音频，这样你就可以拥有完整的细粒度控制。|offset|length|1850860|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Image:Mp3filestructure.svg^0|0|0|2P|F|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@$F|S|G|T|1|U]]|A|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]]]

Mp3 is lossy, but it is lossy in a very specific way. The algorithms used as designed to discard certain parts of the audio which your ears are unable to hear (or are very difficult to hear). Re-doing the compression process at the same level of compression over and over is likely to yield nearly identical results for a given piece of audio. However, some additional losses may slowly accumulate. If you're going to be modifying files a lot, this might be a bad idea. It would also be a bad idea if you were concerned about quality, but then using MP3 if you are concerned about quality is a bad idea over all.

You could construct a test using an encoder and a decoder to re-encode a few different mp3 files a few times and watch how they change, this could help you determine the rate of deterioration and figure out if it is acceptable to you. Sounds like you have libraries you could use to run this simple test already.

MP3 files are composed of "frames" of audio and so it should be possible, with some effort, to remove entire frames with minimal processing (remove the frame, update some minor details in the file header). I believe frames are pretty short (a few milliseconds each) which would give the precision you're looking for. So doing some reading on the <a href="http://en.wikipedia.org/wiki/Image:Mp3filestructure.svg" rel="nofollow noreferrer">MP3 File Format</a> should give you enough information to code your own python library to do this. This is a fair bit different than traditional "audio processing" (since you don't care about precision) and so you're unlikely to find an existing library that does this. Most, as you've found, will decompress the audio first so you can have complete fine-grained control.

blocks|key|2064950|text|不能直接满足您的需求，但请检查执行您想要的功能的mp3DirectCut软件(作为图形用户界面应用程序)。我认为源代码是可用的，所以即使您找不到库，也可以构建自己的库，或者使用mp3DirectCut中的代码构建python扩展。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2064951|entityMap|0|LINK|mutability|MUTABLE|url|http://mpesch3.de1.cc/mp3dc.html#dwn^0|O|C|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Not a direct answer to your needs, but check the <a href="http://mpesch3.de1.cc/mp3dc.html#dwn" rel="nofollow noreferrer">mp3DirectCut</a> software that does what you want (as a GUI app). I think that the source code is available, so even if you don't find a library, you could build one of your own, or build a python extension using code from mp3DirectCut.

blocks|key|2065357|text|如果你想做一些底层的事情，那就使用pymad。它将MP3s转换为样本数据的缓冲区。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2065358|如果你想要一些更高层次的东西，使用Echo+Nest+Remix+API+(披露:我为我的日常工作写了一部分)。如果您查看cowbell示例(即MoreCowbell.dj)，您将看到一个pymad分支，它给您一个NumPy数组而不是一个缓冲区。这种数据类型使得分割部分和对它们进行数学运算变得更容易。|2065359|entityMap|0|LINK|mutability|MUTABLE|url|http://spacepants.org/src/pymad/|1|http://code.google.com/p/echo-nest-remix/|2|http://code.google.com/p/echo-nest-remix/source/browse/#svn/trunk/examples/cowbell|3|http://morecowbell.dj/|4|http://numpy.scipy.org/^0|H|5|0|0|R|9|1|1P|7|2|20|E|3|2Z|5|4|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@$A|W|B|X|1|Y]]|C|$]]|$1|D|3|E|5|6|7|Z|8|@]|9|@$A|10|B|11|1|12]|$A|13|B|14|1|15]|$A|16|B|17|1|18]|$A|19|B|1A|1|1B]]|C|$]]|$1|F|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]|P|$5|I|J|K|C|$L|Q]]|R|$5|I|J|K|C|$L|S]]|T|$5|I|J|K|C|$L|U]]]]

If you want to do things low-level, use <a href="http://spacepants.org/src/pymad/" rel="nofollow noreferrer">pymad</a>. It turns MP3s into a buffer of sample data.

If you want something a little higher-level, use the Echo Nest <a href="http://code.google.com/p/echo-nest-remix/" rel="nofollow noreferrer">Remix API</a> (disclosure: I wrote part of it for my dayjob). It includes a few examples. If you look at the <a href="http://code.google.com/p/echo-nest-remix/source/browse/#svn/trunk/examples/cowbell" rel="nofollow noreferrer">cowbell</a> example (i.e., <a href="http://morecowbell.dj" rel="nofollow noreferrer">MoreCowbell.dj</a>), you'll see a fork of pymad that gives you a <a href="http://numpy.scipy.org/" rel="nofollow noreferrer">NumPy</a> array instead of a buffer. That datatype makes it easier to slice out sections and do math on them.

blocks|key|2065382|text|至于从mp3文件中删除或提取mp3段，同时保留在PCM域中(即不需要来回转换MP3格式)，还有一个开放源码包PyMp3Cut。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2065383|至于将MP3文件拼接在一起(添加例如我发现只要mp3文件具有相同的采样率(例如，44.1+the+)和相同的声道数量(例如，两个都是立体声，或者两个都是单声道)，你就可以简单地连接这些‘Credits文件。|2065384|entityMap|0|LINK|mutability|MUTABLE|url|http://sourceforge.net/projects/pymp3cut/^0|1I|8|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

As for removing or extracting mp3 segments from an mp3 file while staying in the MP3 domain (that is, without conversion to PCM format and back), there is also the open source package <a href="http://sourceforge.net/projects/pymp3cut/" rel="nofollow noreferrer">PyMp3Cut</a>. 

As for splicing MP3 files together (adding e.g. 'Credits' to the end or beginning of an mp3 file) I've found you can simply concatenate the MP3 files providing that the files have the same sampling rate (e.g. 44.1khz) and the same number of channels (e.g. both are stereo or both are mono).

I am looking for some general advice about the mp3 format before I start a small project to make sure I am not on a wild-goose chase.

My understanding of the internals of the mp3 format is minimal. Ideally, I am looking for a library that would abstract those details away. I would prefer to use Python (but could be convinced otherwise).

I would like to modify a set of mp3 files in a fairly simple way. I am not so much interested in the ID3 tags but in the audio itself. I want to be able to delete sections (e.g. drop 10 seconds from the 3rd minute), and insert sections (e.g. add credits to the end.)

My understanding is that the mp3 format is lossy, and so decoding it to (for example) PCM format, making the modifications, and then encoding it again to MP3 will lower the audio quality. (I would love to hear that I am wrong.)

I conjecture that if I stay in mp3 format, there will be some sort of minimum frame or packet-size to deal with, so the granularity of the operations may be coarser. I can live with that, as long as I get an accuracy of within a couple of seconds.

I have looked at <a href="http://pymedia.org/" rel="noreferrer">PyMedia</a>, but it requires me to migrate to PCM to process the data. Similarly, <a href="http://lame.sourceforge.net" rel="noreferrer">LAME</a> wants to help me encode, but not access the data in place. I have seen several other libraries that only deal with the ID3 tags.

Can anyone recommend a Python MP3 library? Alternatively, can you disabuse me of my assumption that going to PCM and back is bad and avoidable?

Python library to modify MP3 audio without transcoding

Python

在我开始一个小项目之前，我正在寻找一些关于mp3格式的一般建议，以确保我不是在白费力气。我对mp3格式的内部原理的了解很少。理想情况下，我正在寻找一个能够将这些细节抽象出来的库。我更喜欢使用Python (但也可以被说服)。我想以一种相当简单的方式修改一组mp3文件。我对ID3标签不是很感兴趣，而是对音频本身感兴趣。我...

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