mp2enc1

Usage

Overview

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.