将M4a采样率更改为自定义值 [英] Changing M4a sampling rate to a customized value

问题描述

我正在尝试将M4a文件的采样率从44100Hz更改为自定义值，例如51200Hz.我使用了可以在WAV采样率转换中正常工作的followingng命令:

  ffmpeg -i audio.m4a -ar 51200 audio_51200.m4a 

不幸的是，它会生成一个采样率为48000 Hz的文件.有什么想法吗?

解决方案

AAC配置文件的频率集有限.例如，HE AAC:

选择采样频率的建议:

I am trying to change the sampling rate of an M4a file from 44100Hz to a customized value let's say 51200Hz. I used the followng command which worked fine with wav sampling rate conversion:

ffmpeg -i audio.m4a -ar 51200 audio_51200.m4a

Unfortunately, it generates a file with a 48000 Hz sampling rate. Any ideas?

解决方案

There is a limited set of frequencies for AAC profiles. For example for HE AAC:

http://www.atsc.org/wp-content/uploads/2015/03/A153-Part-8-2012.pdf

So ffmpeg adjust any non-standard frequency to nearest available

Update: The set of available sampling frequencies is limited by AAC ADIF (Audio Data Interchange Format) and ADTS (Audio Data Transport Stream). So other rates just can't be encoded. Here are values for field sampling_frequency_index form subclause 8.1.1.2 in ISO/IEC 13818-7 standard:

Recommendations for selecting sample frequency:

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