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bitrate
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-b n
For MPEG-1 (sampling frequencies of 32, 44.1 and 48 kHz)
n = 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320
For MPEG-2 and MPEG-2.5 (sampling frequencies of 8, 11.025,
12, 16, 22.05 and 24 kHz)
n = 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160
The bitrate to be used. Default is 128 kbps MPEG1, 80 kbps 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.
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max bitrate
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-B n
see also option "-b" for allowed bitrates.
Maximum allowed bitrate when using VBR/ABR.
Using -B is NOT RECOMMENDED. A 128 kbps CBR bitstream, because of the
bit reservoir, can actually have frames which use as many bits as a
320 kbps frame. ABR/VBR modes minimize the use of the bit reservoir, and
thus need to allow 320 kbps frames to get the same flexability as CBR
streams.
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fast mode
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-f
Same as -q 7.
NOT RECOMMENDED. Use when encoding speed is critical and encoding
quality does not matter. Disable noise shaping. Psycho acoustics are
used only for bit allocation and pre-echo detection.
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strictly enforce VBR minimum bitrate
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-F
strictly enforce VBR minimum bitrate. With out this optioni, the minimum
bitrate will be ignored for passages of analog silence.
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high quality
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-h
use some quality improvements. The same as -q 2.
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keep all frequencies
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-k
keep all frequencies. (Disable all filters)
LAME will automatically apply various types of lowpass filters. This
is because the high frequency coefficients can take up a lot of bits
that would be better used for lower, more important frequencies.
-k will disable all lowpass filtering. Not recommended.
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Modes:
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-m m mono
-m s stereo
-m j joint stereo
-m f forced mid/side stereo
-m d dual (independent) channels
-m i intensity stereo
-m a auto
MONO is the default mode for mono input files. If "-m m" is specified
for a stereo input file, the two channels will be averaged into a mono
signal.
STEREO
JOINT STEREO is the default mode for stereo files with fixed bitrates of
128 kbps or less. At higher fixed bitrates, the default is stereo.
For VBR encoding, jstereo is the default for VBR_q >4, and stereo
is the default for VBR_q <=4. You can override all of these defaults
by specifing the mode on the command line.
jstereo means the encoder can use (on a frame by frame bases) either
regular stereo (just encode left and right channels independently)
or mid/side stereo. In mid/side stereo, the mid (L+R) and side (L-R)
channels are encoded, and more bits are allocated to the mid channel
than the side channel. This will effectively increase the bandwidth
if the signal does not have too much stereo separation.
Mid/side stereo is basically a trick to increase bandwidth. At 128 kbps,
it is clearly worth while. At higher bitrates it is less useful.
For truly mono content, use -m m, which will automatically down
sample your input file to mono. This will produce 30% better results
over -m j.
Using mid/side stereo inappropriately can result in audible
compression artifacts. To much switching between mid/side and regular
stereo can also sound bad. To determine when to switch to mid/side
stereo, LAME uses a much more sophisticated algorithm than that
described in the ISO documentation.
FORCED MID/SIDE STEREO forces all frames to be encoded mid/side stereo. It
should only be used if you are sure every frame of the input file
has very little stereo seperation.
DUAL CHANNELS Not supported.
INTENSITY STEREO
AUTO
Auto select should select (if input is stereo)
8 kbps Mono
16- 96 kbps Intensity Stereo (if available, otherwise Joint Stereo)
112-128 kbps Joint Stereo -mj
160-192 kbps -mj with variable mid/side threshold
224-320 kbps Independent Stereo -ms