Message ID | 20200511133445.95631-1-guillaume.kh.alt@gmail.com |
---|---|
State | New |
Headers | show |
Series | [FFmpeg-devel] doc/encoders: ffaacenc does not output CBR | expand |
Context | Check | Description |
---|---|---|
andriy/default | pending | |
andriy/make | success | Make finished |
andriy/make_fate | success | Make fate finished |
May 11, 2020, 14:34 by guillaume.kh.alt@gmail.com: > The documentation and wiki imply the native AAC encoder can output CBR and VBR files : > >b > >Set bit rate in bits/s. Setting this automatically activates constant bit rate (CBR) mode. If this option is unspecified it is set to 128kbps. > >> >> > >q > >Set quality for variable bit rate (VBR) mode. This option is valid only using the ffmpeg command-line tool. For library interface users, use global_quality. > The twoloop coder (not the default) does CBR. The fast coder for now tries to approximate it. So the documentation is correct. If you do need more accurate CBR just use the twoloop coder for now. I'm working on the encoder now and that should improve its CBR constraints with the fast coder.
diff --git a/doc/encoders.texi b/doc/encoders.texi index aa3a6eeb66..44ff5e469b 100644 --- a/doc/encoders.texi +++ b/doc/encoders.texi @@ -30,17 +30,19 @@ follows. Advanced Audio Coding (AAC) encoder. -This encoder is the default AAC encoder, natively implemented into FFmpeg. +This encoder is the default AAC encoder, natively implemented into FFmpeg. It +supports a constrained variable bit rate mode and a true variable bit (VBR) +rate mode. @subsection Options @table @option @item b -Set bit rate in bits/s. Setting this automatically activates constant bit rate -(CBR) mode. If this option is unspecified it is set to 128kbps. +Set maxmimum bit rate in bits/s. Setting this automatically activates constrained +variable bit rate mode. If this option is unspecified it is set to 128kbps. @item q -Set quality for variable bit rate (VBR) mode. This option is valid only using +Set quality for true variable bit rate (VBR) mode. This option is valid only using the @command{ffmpeg} command-line tool. For library interface users, use @option{global_quality}.