mp2enc

Section: MJPEG tools manual (1)
Updated: 2 June 2001
Page Index

NAME

mp2enc - Simple MPEG-1 layer-II audio encoder

SYNOPSIS

mp2enc [-v num] [-b bitrate_kbps] [-r output_sampling_rate_hz] [-R rate,chans,bits] [-s ] [-m ] [-e ] [-V ] [-?] -o output_filename

DESCRIPTION

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 mjpegtools(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:

http://www.planckenergy.com

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.

-s

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.

-m

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.

-e

Use CRC error protection.

-V

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.

BUGS

Mono output does not work for layer I.

AUTHOR

This man page was written by Andrew Stevens.
If you have questions, remarks, problems or you just want to contact the developers, the main mailing list for the MJPEG-tools is:
mjpeg-users@lists.sourceforge.net

For more info, see our website at: http://mjpeg.sourceforge.net