NAME

mp3enc − create mp3 audio files

SYNOPSIS

­games/mp3enc [ ­-hprv ] [ ­-b ­bitrate ] [ ­-B ­bitrate ] [ ­-m ­mode ] [ ­-q q ] [ ­-s ­sfreq ] [ ­-V ­q ] [ ­long or silly options ]

DESCRIPTION

­Mp3enc compresses audio on standard input, normally PCM-encoded, and produces MP3-encoded audio on standard output.  By default, the MP3 file will use ‘constant bit-rate’ (CBR) encoding, but that can be changed via ­--abr (average bitrate desired, ABR) or -v (variable bitrate, VBR). 

Options

­-b set minimum allowed ­bitrate in Kb/s for VBR, default 32Kb/s.  For CBR, set the exact bitrate in Kb/s, which defaults to 128Kb/s. 

­-B set maximum allowed ­bitrate in Kb/s for VBR, default 256Kb/s. 

-h same as -q 2. 

­-m ­mode may be (s)tereo, (j)oint, (f)orce or (m)ono (default j).  ­force forces mid/side stereo on all frames. 

­-p add CRC error protection (adds an additional 16 bits per frame to the stream).  This seems to break playback. 

­-q sets output quality to ­q (see -V). 

­-r input is raw pcm

­-s set sampling frequency of input file (in KHz) to sfreq, default is 44.1.

­-v use variable bitrate (VBR) encoding

­-V set quality setting for VBR to q. Default ­q is 4; 0 produces highest-quality and largest files, and 9 produces lowest-quality and smallest files. 

Long options

--abr bitrate sets average ­bitrate desired in Kb/s, instead of setting quality, and generates ABR encoding. 

--resample sfreq set sampling frequency of output file (in KHz) to sfreq, default is input sfreq.

--mp3input ­input is an MP3 file

Silly options

-f same as -q 7.  Such a deal. 

-o mark as non-original (i.e. do not set the original bit)

-c mark as copyright

-k disable sfb=21 cutoff

-e emp de-emphasis n/5/c (default n)

-d allow channels to have different blocktypes

-t disable Xing VBR informational tag

-a autoconvert from stereo to mono file for mono encoding

-x force byte-swapping of input (see dd(1) instead)

-S don’t print progress report, VBR histograms

--athonly
only use the ATH for masking

--nohist
disable VBR histogram display

--voice experimental voice mode

EXAMPLES

Encode a ­.wav file as highest-quality MP3. 

games/mp3enc -q 0 -b 320

Create a fixed 128Kb/s MP3 file from a ­.wav file. 

games/mp3enc -h <foo.wav >foo.mp3

Streaming from stereo 44.1KHz raw PCM data, encoding mono at 16KHz (you may not need dd):

dd -conv swab | games/mp3enc -a -r -m m --resample 16 -b 24

SOURCE

­/sys/src/games/mp3enc

SEE ALSO

dd(1), mp3dec(1), audio(3), cdfs(4), audio(7), juke(7), playlistfs(7)
­http://www.sulaco.org/mp3

BUGS

Quality is much better than encoders based on the ISO routines, but still not as good as the FhG encoder. 

It’s a GNU behemoth, lightly rehabilitated.  There are zillions of undocumented options. 

Plan 9  —  March 14, 2011