Question

我需要在需要导入Python（ndarray）的Android应用程序中录制音频以进行绘图和信号处理。这看起来很简单。
我从AAC / MPEG4录制的简单代码开始。录音效果很好。我可以在Android手机（Nexus 5X）和Mac（Quicktime）上播放。没问题！对？！？但是找到Android和Python之间匹配的编解码器/格式似乎并不是微不足道的。我想知道Android编写的文件/编解码器格式是否是非标准格式，而FFMPEG无法读取它。
如果是这样，什么是好的音频格式/编解码器，可以简单地在Android中编写并在Python（2.7.x）中读入数组。感谢。

详细说明：这是android代码的缩写形式：

private final int AUDIO_SAMPLE_RATE = 16000;   
private final String FILE_EXTENSION = "m4a";  // Audio file extension
mAbsolutePathFile = workingDir + "/" + mFilename + FILE_EXTENSION;
mMediaRecording = new MediaRecorder();
mMediaRecording.setAudioSource (MediaRecorder.AudioSource.MIC);
mMediaRecording.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
mMediaRecording.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
mMediaRecording.setAudioSamplingRate(AUDIO_SAMPLE_RATE);
mMediaRecording.setOutputFile(mAbsolutePathFile);
mMediaRecording.prepare();
mMediaRecording.start();

正如我所提到的，结果音频在Android和MacOS中都很好用，所以一切都很顺利。我做了一些搜索，找到了AAC音频的python包，pydub看起来最简单（我试过audiotools，但无法找到示例代码）。要安装pydub，我按照instructions：

进行了操作

pip install pydub

和

brew install libav --with-libvorbis --with-sdl --with-theora

和

brew install ffmpeg --with-libvorbis --with-ffplay --with-theora

在讨论（here）之后，我测试了ffmpeg，它确实从命令行执行：

  $ffmpeg
  ffmpeg version 3.2.2 Copyright (c) 2000-2016 the FFmpeg developers
  built with Apple LLVM version 8.0.0 (clang-800.0.42.1)

但是当我尝试使用Python读取文件时：

import pydub
pydub.AudioSegment.from_file("sensorlog_2017-02-03_12-50-25-345_Dev26c5_Loc27_TypeAUDIO.m4a", "aac")

我明白了：

Traceback (most recent call last):
  File "...anaconda2/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 2881, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-8-607e3f2a62c3>", line 1, in <module>
pydub.AudioSegment.from_file("sensorlog_2017-02-03_12-50-25-345_Dev26c5_Loc27_TypeAUDIO.m4a", "aac")
File ".../anaconda2/lib/python2.7/site-packages/pydub/audio_segment.py", line 472, in from_file
    raise CouldntDecodeError("Decoding failed. ffmpeg returned error code: {0}\n\nOutput from ffmpeg/avlib:\n\n{1}".format(p.returncode, p_err))
CouldntDecodeError: Decoding failed. ffmpeg returned error code: 1
Output from ffmpeg/avlib:
avconv version 11.4, Copyright (c) 2000-2014 the Libav developers
  built on Feb  3 2017 12:09:15 with Apple LLVM version 8.0.0 (clang-800.0.42.1)
[aac @ 0x7ff30001cc00] get_buffer() failed
[aac @ 0x7ff30001cc00] channel element 3.14 is not allocated
[aac @ 0x7ff30001cc00] Sample rate index in program config element does not match the sample rate index configured by the container.
[aac @ 0x7ff30001cc00] Input buffer exhausted before END element found
[aac @ 0x7ff30001cc00] More than one AAC RDB per ADTS frame is not implemented. Update your Libav version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[aac @ 0x7ff30001cc00] Error decoding AAC frame header.
[aac @ 0x7ff300001000] Could not find codec parameters (Audio: aac, 4.0, fltp, 213 kb/s)
[aac @ 0x7ff300001000] Estimating duration from bitrate, this may be inaccurate
/var/folders/cm/1r6x6rbj7hn_51qvfjzj7nx80000gn/T/tmps7b8Gf: could not find codec parameters

总之，这是Android和FFMPEG之间的冲突吗？我应该使用不同的编解码器/格式吗？我应该使用不同的Python音频库吗？感谢。

Answer 1

在pydub的GitHub issues中还有一些额外的讨论，但对于未来的流浪者，我相信解决方案是使用＆＃34; mp4＆＃34;作为格式

from pydub import AudioSegment
sound = AudioSegment.from_file("./sensorlog.m4a", format="mp4")

旁注：如果你无法找出正确的格式，你可以完全省略格式参数，pydub / ffmpeg / avconv /无论谁想要弄明白。

sound = AudioSegment.from_file("./sensorlog.m4a")

您可能会发现尝试pydub.utils.mediainfo()很有用，但根据您的ffmpeg / avconv安装它可能会或可能不会（它在内部使用ffprobe）

>>> from pydub.utils import mediainfo

>>> mediainfo("./sensorlog.m4a")

{u'DISPOSITION': {u'attached_pic': u'0',
  u'clean_effects': u'0',
  u'comment': u'0',
  u'default': u'1',
  u'dub': u'0',
  u'forced': u'0',
  u'hearing_impaired': u'0',
  u'karaoke': u'0',
  u'lyrics': u'0',
  u'original': u'0',
  u'timed_thumbnails': u'0',
  u'visual_impaired': u'0'},
 u'TAG': {u'com.android.version': u'7.0',
  u'compatible_brands': u'isommp42',
  u'creation_time': u'2017-02-03T20:50:33.000000Z',
  u'handler_name': u'SoundHandle',
  u'language': u'eng',
  u'major_brand': u'mp42',
  u'minor_version': u'0'},
 u'avg_frame_rate': u'0/0',
 u'bit_rate': u'15539',
 u'bits_per_raw_sample': u'N/A',
 u'bits_per_sample': u'0',
 u'channel_layout': u'mono',
 u'channels': u'1',
 u'codec_long_name': u'AAC (Advanced Audio Coding)',
 u'codec_name': u'aac',
 u'codec_tag': u'0x6134706d',
 u'codec_tag_string': u'mp4a',
 u'codec_time_base': u'1/8000',
 u'codec_type': u'audio',
 u'duration': u'7.808000',
 u'duration_ts': u'62464',
 u'filename': u'/Users/jiaaro/Downloads/sensorlog_2017-02-03_12-50-25-345_Dev26c5_Loc27_ActvAppTesting_TypeAUDIO.m4a',
 u'format_long_name': u'QuickTime / MOV',
 u'format_name': u'mov,mp4,m4a,3gp,3g2,mj2',
 u'id': u'N/A',
 u'index': u'0',
 u'max_bit_rate': u'12200',
 u'nb_frames': u'61',
 u'nb_programs': u'0',
 u'nb_read_frames': u'N/A',
 u'nb_read_packets': u'N/A',
 u'nb_streams': u'1',
 u'probe_score': u'100',
 u'profile': u'LC',
 u'r_frame_rate': u'0/0',
 u'sample_fmt': u'fltp',
 u'sample_rate': u'8000',
 u'size': u'15167',
 u'start_pts': u'0',
 u'start_time': u'0.000000',
 u'time_base': u'1/8000'}

Android：在Android中录制音频，然后将音频读入python

1 个答案: