I tried encoding audio stream into AAC with a variable bitrate mode — I followed the advice from FFmpeg VBR Settings and changed my original option -b:a 128k
to -q:a 1.3
in this original command
ffmpeg -channel_layout stereo -i sc2.avs -b:a 128k -ar 24000 -ac 2 sc2.mp4
But I still obtained a constant audio bitrate.
Output from MediaInfo:
Audio ID : 2 Format : AAC LC Format/Info : Advanced Audio Codec Low Complexity Codec ID : mp4a-40-2 Duration : 1 min 26 s Duration_LastFrame : -29 ms Bit rate mode : Constant Bit rate : 119 kb/s Channel(s) : 2 channels Channel layout : L R Sampling rate : 24.0 kHz Frame rate : 23.438 FPS (1024 SPF) Compression mode : Lossy Stream size : 1.23 MiB (8%) Default : Yes Alternate group : 1
The Any Video Converter (the old version 3.5.8), which internally uses FFmpeg, convert the same input into VBR mode:
Audio ID : 2 Format : AAC LC Format/Info : Advanced Audio Codec Low Complexity Codec ID : mp4a-40-2 Duration : 1 min 26 s Bit rate mode : Variable Bit rate : 75.3 kb/s Maximum bit rate : 142 kb/s Channel(s) : 2 channels Channel layout : L R Sampling rate : 24.0 kHz Frame rate : 23.438 FPS (1024 SPF) Compression mode : Lossy Stream size : 778 KiB (9%) Language : English Encoded date : UTC 2019-12-19 13:30:13 Tagged date : UTC 2019-12-19 13:30:13
How to reach VBR audio output?
(I need it because of Dissolve()
function in AviSynth source file produces horrible sound for CBR, whereas it's nice for Any Video Converter's VBR audio output.)