Version 5 (modified by llogan, 6 years ago) (diff)

nits and additional info on qscale:a range

VBR Encoding

Example to encode VBR MP3 audio with ffmpeg using the libmp3lame library:

ffmpeg -i input.wav -codec:a libmp3lame -qscale:a 2 output.mp3

Control quality with -qscale:a (or the alias -q:a). Values are encoder specific, so for libmp3lame the range is 0-9 where a lower value is a higher quality. 0-3 will normally produce transparent results, 4 (default) should be close to perceptual transparency, and 6 produces an "acceptable" quality. The option -qscale:a is mapped to the -V option in the standalone lame command-line interface tool.

LAME Bitrate Overview
Option Kbit/s Bitrate range kbit/s
-b 320 320 320 CBR
-V 0 245 220...260
-V 1 225 190...250
-V 2 190 170...210
-V 3 175 150...195
-V 4 165 140...185
-V 5 130 120...150
-V 6 115 100...130
-V 7 100 80...120
-V 8 85 70...105
-V 9 65 45...85

In our example above, we selected -qscale:a 2, meaning we used LAME's option -V2, which gives us a VBR MP3 audio stream with an average stereo bitrate of 170-210 kBit/s.

CBR Encoding

If you need constant bitrate (CBR) MP3 audio, you need to use the -b:a option instead of -qscale:a. Here you can specify the number of bits per second, for example -b:a 256k if you want 256 kBit/s audio.

Also see