FFmpeg录制音频

最近在学习怎么用FFmpeg录制音频，在按照网上教程整理过程中碰到一些问题，以下集中记录下录制音频时碰到的一些问题。

 

• 在调用FFmpeg的avformat_open_input函数时，由于设置options这个参数，然后程序立即报这个错误：

[dshow @ 0000026cebd068c0] Could not set audio only options
[dshow @ 0000026cebd068c0] Searching for audio device within video devices for virtual-audio-capturer
[dshow @ 0000026cebd068c0] Could not find audio only device with name [virtual-audio-capturer] among source devices of type video.

由提示可以知道肯定是options这个参数设置有问题，而我只参照其他文档只设置了一项：

ret = av_dict_set(&dict, "sample_rate", "44100", 0);

在网上搜了下查看本设备的详细参数的命令：

>ffmpeg -f dshow -list_options 1 -i audio="virtual-audio-capturer"
ffmpeg version 6.0-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
......
  libpostproc    57.  1.100 / 57.  1.100
[dshow @ 000001761dca7e40] DirectShow audio only device options (from audio devices)
[dshow @ 000001761dca7e40]  Pin "Capture Virtual Audio Pin" (alternative pin name "1")
[dshow @ 000001761dca7e40]   ch= 2, bits=16, rate= 48000
audio=virtual-audio-capturer: Immediate exit requested

发现仅支持采样率仅支持48000，原来不能和这个值不一样。

既然如此，那干脆就采用默认值算了，有需求的话再重采样。

 

• avformat_write_header fail.  Error ret: -22 , info:  Invalid argument

完整提示如下：

avformat_write_header fail.  Error ret: -22 , info:  Invalid argument
[dshow @ 0000022ddb8368c0] Selecting pin Capture Virtual Audio Pin on audio only
[dshow @ 0000022ddb8368c0] passing through packet of type audio size     1920 timestamp 294129990000 orig timestamp 294129990000 graph timestamp 294130090000 diff 100000 virtual-audio-capturer
[dshow @ 0000022ddb8368c0] All info found
[file @ 0000022ddb827f00] Setting default whitelist 'file,crypto,data'
Output #0, mp3, to '2_16_48000.mp3':
  Stream #0:0, 0, 0/0: Unknown: none
[mp3 @ 0000022ddb83a2c0] Only audio streams and pictures are allowed in MP3.
[AVIOContext @ 0000022ddb87b300] Statistics: 0 bytes written, 0 seeks, 0 writeouts
Received stop event after 2 passes

错误提示在avformat_write_header处，错误是参数错误，但是由于第一次搞这块，实在没看懂哪个参数有问题。

然后只能把这些提示一行行去搜，终于用Only audio streams and pictures are allowed in MP3.搜到一份源代码。

 突然醒悟过来，的确我从网上抄来的代码没有设置codecpar这个参数，那么只需要把这个参数给设置上就可以了。