以下摘自 ffmpeg-full-document。
"""
Advanced Audio Coding (AAC) encoder.
This encoder is the default AAC encoder, natively implemented into FFmpeg. Its quality is on par or better than libfdk_aac at the default bitrate of 128k
bp
s. This encoder also implements more options, profiles and samplerates than other encoders (with only the AAC-HE profile pending to be implemented) so this encoder has become the default and is the recommended choice.
"""

wiki里面有另外一段描述。我向来是人耳听声，没有感觉太多玄学差别，有研究频谱的同学可以验证下。
"""
The bitrates listed here assume 2-channel stereo and a sample rate of 44.1kHz or 48kHz. Mono, speech, and quiet audio may require fewer bits.
* libopus Usable range >= 80Kbps. Recommended range >= 128Kbps
* libfdk_aac default AAC LC profile. Recommended range >= 128Kbps; see AAC Encoding Guide.
* libfdk_aac -profile:a aac_he_v2 Usable range <= 48Kbps CBR. Transparency: Does not reach transparency. Use AAC LC instead to achieve transparency
* libfdk_aac -profile:a aac_he Usable range >= 48Kbps and <= 80Kbps CBR. Transparency: Does not reach transparency. Use AAC LC instead to achieve transparency
* libvorbis Usable range >= 96Kbps. Recommended range -aq 4 (>= 128Kbps)
* libmp3lame Usable range >= 128Kbps. Recommended range -aq 2 (>= 192Kbps)
* ac3 or eac3 Usable range >= 160Kbps. Recommended range >= 160Kbps
"""

确实是属于能用水平

能vbr么

听说ffmpeg的重写vp系列编码没谷歌那么啰嗦，能省略n行代码，音频编码有没有省略就不知道了

64k 码率的情况下， faac 比 ffmpeg 好多了。压个老友记，ffmpeg 的连说话声音都听不清楚