usage

MP3编码程序和资料

% lame [options] inputfile [outputfile]

=======================================================================
Examples:
=======================================================================
fixed bit rate jstereo 128kbs encoding:
% lame sample.wav  sample.mp3      

fixed bit rate jstereo 128kbs encoding, highest quality:  (recommended)
% lame -h sample.wav  sample.mp3      

To disable joint stereo encoding (slightly faster, but less quality at bitrates<=128kbs)
% lame -m s sample.wav  sample.mp3     

Fast encode, low quality  (no psycho-acoustics)
% lame -f sample.wav  sample.mp3     

Variable Bitrate (VBR): (use -V n to adjust quality/filesize)
% lame -h -v sample.wav sample.mp3

Note: VBR is currently under heavy development.  Right now it can
often result in too much compression.  I would recommend using VBR
with a minimum bitrate of 112kbs.  This will let LAME increase
the bitrate for difficult-to-encode frames, but prevent LAME from
being too aggressive for simple frames:

% lame -h -v -b 112  sample.wav sample.mp3


=======================================================================
LOW BITRATES
=======================================================================
At lower bitrates, (like 24kbs per channel), it is recommended that
you use a 16kHz sampling rate combined with lowpass filtering.  LAME,
as well as commercial encoders (FhG, Xing) will do this automatically.
However, if you feel there is too much (or not enough) lowpass
filtering, you may need to try different values of the lowpass cutoff
and passband width (--resample, --lowpass and --lowpass-width options).


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STREAMING EXAMPLES
=======================================================================

% cat inputfile | lame [options] - - > output




=======================================================================

For more options, just type:
% lame --help

Scripts are included to run lame on multiple files:

bach script:  mlame     Run "mlame -h" for instructions.
sh script:    auenc     Run auenc for instructions



=======================================================================
options guide:
=======================================================================
These options are explained in detail below.


Quality related:

-m m/s/j/f     mode selection
-k             disable all filtering
-d             allow block types to differ between channels
--athonly      ignore psy-model output, only use masking from the ATH
--voice        experimental voice encoding mode
--noshort      disable short blocks


Constant Bit Rate (CBR)
-b  n          set bitrate (8,16,24,...,320)
-h             higher quality but slower
-f             disable noise shaping.  Encodes faster, but lower quality
--freeformat   produce a free format bitstream.  User must also specify
               a bitrate with -b, between 8 and 320 kbs.

Variable Bit Rate (VBR)
-v             VBR
--vbr-old      use old variable bitrate (VBR) routine
-V n           VBR quality setting  (0=highest quality, 9=lowest)
-b  n          specify a minimum allowed bitrate (8,16,24,...,320)
-B  n          specify a maximum allowed bitrate (8,16,24,...,320)
-F             strictly enforce minimum bitrate
-t             disable Xing VBR informational tag 
--nohist       disable display of VBR bitrate histogram

--abr n        specify average bitrate desired


Experimental (undocumented):  may work better or worse:

-X n           try different quality measures (when comparing quantizations)
-Y             
-Z             


Operational:

-r             assume input file is raw PCM
--decode       assume input file is an mp3 file, and decode to raw pcm.  
-s  n          input sampling frequency in kHz (for raw PCM input files)
--resample n   output sampling frequency
--mp3input     input file is an MP3 file.  decode using mpglib/mpg123
--ogginput     input file is an Ogg Vorbis file.  decode using libvorbis
-x             swap bytes of input file
-a             downmix stereo input file to mono .mp3
-e  n/5/c      de-emphasis
-p             add CRC error protection
-c             mark the encoded file as copyrighted
-o             mark the encoded file as a copy
-S             don't print progress report, VBR histogram
-g             run MP3x, the graphical frame analyzer
--strictly-enforce-ISO   comply as much as possible to ISO MPEG spec

--ogg          Encode using Ogg Vorbis (.ogg) instead of mp3.

id3 tagging:

--tt "title"     title of song (max 30 chars)
--ta "artist"    artist who did the song (max 30 chars)
--tl "album"     album where it came from (max 30 chars)
--ty "year"      year in which the song/album was made (max 4 chars)
--tc "comment"   additional info (max 30 chars)
--tg "genre"     genre of song (name or number)



options not yet described:
--nores            disable bit reservoir
--noath            disable ATH
--cwlimit <freq>   specify range of tonality calculation

--lowpass
--lowpass-width
--highpass
--highpass-width





=======================================================================
Detailed description of all options in alphabetical order
=======================================================================


=======================================================================
downmix
=======================================================================
-a  

mix the stereo input file to mono and encode as mono.  

This option is only needed in the case of raw PCM stereo input 
(because LAME cannot determine the number of channels in the input file).
To encode a stereo PCM input file as mono, use "lame -m s -a"

For WAV and AIFF input files, using "-m m" will always produce a
mono .mp3 file from both mono and stereo input.


=======================================================================
average bitrate encoding (aka Safe VBR)
=======================================================================
--abr n

turns on encoding with a targeted average bitrate of n kbits, allowing
to use frames of different sizes.  The allowed range of n is 4-310,
you can use any integer value within that range.

It can be combined with the -b and -B switches like
lame --abr 123 -b 64 -B 192 a.wav a.mp3
which would limit the allowed frame sizes between 64 and 192 kbits.

Using -B is NOT RECOMMENDED.  A 128kbs CBR bitstream, because of the
bit reservoir, can actually have frames which use as many bits as a
320kbs frame.  VBR modes minimize the use of the bit reservoir, and
thus need to allow 320kbs frames to get the same flexability as CBR
streams.




=======================================================================
ATH only
=======================================================================
--athonly

This option causes LAME to ignore the output of the psy-model and
only use masking from the ATH.  Might be useful at very high bitrates
or for testing the ATH.  




=======================================================================
bitrate
=======================================================================
-b  n

For MPEG1 (sampling frequencies of 32, 44.1 and 48kHz)
n =   32,40,48,56,64,80,96,112,128,160,192,224,256,320

For MPEG2 (sampling frequencies of 16, 22.05 and 24kHz)
n = 8,16,24,32,40,48,56,64,80,96,112,128,144,160


The bitrate to be used.  Default is 128kbs MPEG1, 80kbs MPEG2.

When used with variable bitrate encodings (VBR), -b specifies the
minimum bitrate to use.  This is useful to prevent LAME VBR from
using some very aggressive compression which can cause some distortion
due to small flaws in the psycho-acoustic model.

=======================================================================
max bitrate
=======================================================================
-B  n

For MPEG1 (sampling frequencies of 32, 44.1 and 48kHz)
n =   32,40,48,56,64,80,96,112,128,160,192,224,256,320

For MPEG2 (sampling frequencies of 16, 22.05 and 24kHz)
n = 8,16,24,32,40,48,56,64,80,96,112,128,144,160

Maximum allowed bitrate when using VBR.


=======================================================================
copyright
=======================================================================
-c   

mark the encoded file as copyrighted



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block type control
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-d 

Allows the left and right channels to use different block types.
Normally this is not allowed, only because the FhG encoder does
not seem to allow it either.  If anyone finds a sample where -d
produces better results, let me know.  ([e-mail])


=======================================================================
mpglib decode capability
=======================================================================
--decode 

This just uses LAME's mpg123/mpglib interface to decode an MP3 file to
a raw pcm file.  The input file must be an MP3 file, and the raw pcm
data will be written to the output file in native endian format.
Under linux, on i386, to convert the output file to a wav, use:

% lame --decode input.mp3 output.pcm
% sox -c 2 -t raw -r 44100 -s -w output.pcm output.wav

(assuming output.pcm came from a stereo, 44.1khz mp3 file)



=======================================================================
de-emphasis
=======================================================================
-e  n/5/c   

  n = (none, default)
  5 = 0/15 microseconds
  c = citt j.17

All this does is set a flag in the bitstream.  If you have a PCM
input file where one of the above types of (obsolete) emphasis has
been applied, you can set this flag in LAME.  Then the mp3 decoder
should de-emphasize the output during playback, although most 
decoders ignore this flag.

A better solution would be to apply the de-emphasis with a standalone
utility before encoding, and then encode without -e.  



=======================================================================
fast mode
=======================================================================
-f   

disable noise shaping.  Encodes faster, but lower quality.
Psycho acoustics are computed for bit allocation and 
pre-echo detection.

=======================================================================
strictly enforce VBR minimum bitrate
=======================================================================
-F   

strictly enforce VBR minimum bitrate.  With out this optioni, the minimum
bitrate will be ignored for passages of analog silence.



=======================================================================
free format bitstreams
=======================================================================
--freeformat   

LAME will produce a fixed bitrate, free format bitstream.
User must specify the desired bitrate in kbs, which can
be any integer between 8 and 320.

Not supported by most decoders.  Decoders only required to support
up to 320kbs.  

Decoders which can handle free format:
                     supports up to
"lame --decode"          560kbs  
Freeamp:                 440kbs
l3dec:                   310kbs