Changes between Initial Version and Version 1 of Encoding VBR (Variable Bit Rate) mp3 audio

Timestamp:

07/04/2012 03:48:33 AM (11 months ago)

Author:

burek

Comment:

--

Encoding VBR (Variable Bit Rate) mp3 audio

@@ +1 @@
+To encode VBR mp3 audio with FFmpeg, using libmp3lame library, we would specify a command like this:
+{{{
+ffmpeg -i input.wav -aq 2 out.mp3
+}}}
+
+Option "-aq" needs a parameter, that tells FFmpeg something about expected "audio quality" (of course, this parameter has a different meaning for each audio encoder used, and we are now describing the libmp3lame encoder).
+
+The table for LAME option "-V <num>" is shown here (and that option is mapped to FFmpeg's "-aq" option):
+[http://wiki.hydrogenaudio.org/index.php?title=LAME#VBR_.28variable_bitrate.29_settings]
+
+{{{
+Switch        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
+}}}
+
+So, in our example above, we selected "-aq 2", meaning we used LAME's option "-V 2", which gives a VBR mp3 audio in the range of 170-210 kbit/s.
+
+If you want constant bit rate (CBR) mp3 audio, instead of using "-aq" option, you need to use "-ab" option to set the preferred "audio bit rate" in bps, like "-ab 256k" if you want 256 kbit/s audio.