Section: MJPEG tools manual (1)
Updated: 2 June 2001
mp2enc - Simple MPEG-1 layer-II audio encoder
Mp2enc is a simple MPEG-1 layer-I/II audio encoder. It is actually a very
mildly warmed over version of the MPEG Software Simulation Group's
reference encoder. It accepts a WAV file or stream on stdin and
ouputs an a layer-I/II elementary audio stream. It is included in the
(1) primarily for reasons of completeness and because it
is able to perform sampling rate conversion.
Those seeking a faster (and probably higher quality) layer II encoder are
recommended to use toolame(1) which can be obtained from:
GENERAL FUNCTION LETTERS
- -o output_filename
Specifies the name for the output file.
An integer format code (e.g. %d) in the name is replaced the number of
the file generated (see printf(3)).
- -v num
Set verbosity level to num. 0 = warnings and errors only, 1 = information as well, 2=really verbose.
Display a synopsis of the command syntax.
- -R rate,chans,bits
Indicate, that the input is raw PCM without header. You must specify 3
numbers: rate is the samplerate in Hz, chans is the number of channels
(1 or 2) and bits is the number of bits per sample. 8 bits are unsigned,
16 bits are signed in machine native byte order.
FUNCTION LETTERS CONTROLLING OUTPUT STREAM STRUCTURE
- -b bitrate
This sets the bit-rate of the output stream in kBit/sec. Typical
values for layer II might be 224kbps for good-quality audio suitable for capturing
Dolby pro-logic signals. A rate of 192kbps or 128kbps is reasonable
for low quality audio (e.g. mono TV audio). Really high compression
is, of course, better achieved using MPEG-1 layer III ("MP3") audio
encoding or AAC. A more appropriate value for layer I might be 384kbps.
- -r sampling_rate
Sets the audio sampling rate of the reconstructed output signal in Hz.
Legal values are 32000, 44100 and 48000Hz. mp2enc will automatically
sample-rate convert the input signal if necessary.
- -l layer
Sets the audio layer.
Legal values are 1 and 2. The default is layer II.
Force stereo output. A mono input signal is channel doubled before
encoding to make it stereo. This is useful for players
which simply can't handle a non-stero signal.
Force mono output. A stereo input signal is down-mixed before encoding.
Useful if you've captured a mono signal in stereo and your player can
handle mono MPEG-1 Layer 2 audio.
Use CRC error protection.
Force VCD compatible output. The primary effect of this is to make certain that
the sampling rate is set to 44100 (-r 44100). The VCD2.0 specifications
permit mono audio at 64,
96 and 192 kbits/sec and stereo at 128, 192, 224, and 384 kbits/sec. Using
-V checks that the bitrate is valid for the number of channels.
The defaults (unless -m or -b are used) are stereo at 224 kbits/sec.
- -o outputpathname
The name of the output file to generate. If '-' is given as the pathname output is written to standard output.
Mono output does not work for layer I.
This man page was written by Andrew Stevens.
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