LAME's VBR mode only has advantage over a certain bitrate range. For very low and very high bitrate, use the ABR mode instead.
aac_at's CVBR mode produces very good quality and is not worse than its TVBR mode in blind testing. Use this mode for convenience.
The ffmpeg native aac encoder will have quality regression with its VBR mode. Always use CBR mode for ffmpeg's native aac encoder.
Signed-off-by: gnattu <gnattuoc@me.com>
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