When converting audio files, it would make sense to avoid converting into a higher bitrate, as it is commonly understood that you can never recapture data lost in a previous conversion. Read on to see, however, when upgrading the bitrate is just what the digital doctor ordered.

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问题

超级用户阅读器Cipricus提出了一个问题：

When a certain file (mp4, flv, etc) has a 95 kbps audio bitrate – does it make sense outputing to a higher bitrate when converting to mp3 or other format (be it lossy or not)?

Would this result in higher audio quality or just in a bigger file?

这是一个重要的考虑因素；如果音频质量没有提高，那么将文件大小扩展X%是没有意义的。

答案

超级用户贡献者Linac为他的问题提供了一个实用的答案。尽管流行的观点会让我们相信，但在转换过程中提升比特率还是有实际原因的：

Yes, it might actually make sense if you are being forced to change formats.

If you have a file with 95kbps in a highly efficient format, to retain the same quality, a relatively inefficient format as mp3 needs a higher bitrate.

Of course you will never get anything back that was lost in the first place. On the contrary, encoding as mp3 will reduce the quality further. Every lossy format uses other means to reduce the amount of data that is stored, by (simplified) throwing away “unneeded” parts of the data. Round trip through a bunch of different formats and there won’t be much left …

So if you want to stay as close a possible to the quality your file has now, you should chose a higher bitrate. 320kbps are probably wasted space, but for mp3 something in the order between 128 and 192 is needed to maintain – or at least come close to – the quality of a more efficient 95kbps file.

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