Internet MPEG Audio Archive/IMAA.mdf/util/dos/l3v100n/manual.txt

Text File | 1994-07-18 | 9KB | 204 lines

Manual.txt for Version 1.00 of ISO/MPEG Audio Layer 3 software only
encoder/decoder for PCs.

1. ENCODER
   =======

 L3ENC.EXE is an ISO/MPEG Layer III software only encoder. It takes
 PCM audio data files as input and delivers Layer III coded bit stream
 files as output. Several options can be selected via command line
 switches. Usage:

   L3ENC <PCM audio data> <bitstream> [-switch1 [-switch2 [...]]]

 L3ENC.EXE should work on any IBM PC compatible computer with a 386 type
 CPU or better with external or built in 387 hardware floating point
 support. A 486DX CPU or better is recommended.

 L3ENC uses one of the Dos extenders EMX.EXE or RSX.EXE supplied together
 with this shareware package. EMX.EXE is used for Dos Real Mode and RSX.EXE
 is used for V86 Mode (e.g. Dos Box under Windows). L3ENC automatically
 loads the appropriate extender when started. In order to find the extender,
 L3ENC needs the environment variables EMX and RSX. So before you start
 L3ENC, please execute the commands:
   SET EMX=C:\PATH\EMX.EXE
   SET RSX=C:\PATH\RSX.EXE
 where "C:\PATH\" shows the directory where EMX.EXE and RSX.EXE can be found.

 EMX.EXE is copyright by Eberhard Mattes and RTX.EXE is copyright by
 Rainer Schnither. Please read the documentation supplied with the
 dos extenders for details.

1.1 PCM audio input file
 The first command line argument specifies the name for the PCM audio
 data file. Version 1.00 of the encoder accepts either raw PCM audio
 data files or PCM audio data files in RIFF/WAVE format as used by
 Microsoft Windows. The samples must be 16 bit signed integer values.
 The sampling rate must be 44.1 kHz.

 A) raw PCM audio data
    By default the input file is assumed to contain raw PCM audio data.
    Stereo audio data is input in interleaved format, the first channel
    beeing the left channel.
      <sample #1 channel #1> <s. #1 ch. #2> <s.#2 ch.#1> <s.#2 ch.#2> ...
    Mono audio data has the format
      <sample #1> <sample #2> <sample #3> ....
    Whether the input file is treated as mono or stereo audio data is set
    by the encoding mode parameter (1.3). Default is stereo.

 B) RIFF/WAVE format
    If the '-wav' option is specified, the input file is assumed to contain
    16 bit PCM audio data in RIFF/WAVE format as used by Microsoft Windows.
    Audio parameters are extracted from the Wave header and checked against
    the settings of the encoder. If not supported options are found
    (e.g. 8 bits/sample), the encoding process is aborted. The encoding
    mode (mono or stereo) is determined by the settings in the WAVE header.

1.2 bitstream output file
 The second command line argument specifies the name for the bitstream
 output file. As for now there is no default value for the filename or for
 the extension of the file name. The format of the bit stream is as defined
 in the ISO/MPEG publication IS11172-3.

1.3 encoding mode
 Depending on the setting of the '-mod' switch, the encoder will treat the
 two input channels as:
    -mod 1  stereo (joint stereo),
    -mod 2  mono audio data.

 Default is joint stereo.
 For stereo, the first channel is the left channel. The second channel is
 the right channel.

 If input files in WAVE format are used, the encoding mode is determined by
 the settings in the Wave header.

1.4 sampling rate
 Version 1.00 of the encoder is still restricted to 44.1 kHz.
 Look for support of 32kHz, 44.1 kHz and 48 kHz in the near future.

1.5 bitrate
 The bitrate of the bit stream output is selected via the '-br' switch.  The
 bitrate is specified in bits/second. The bitrate is the total bitrate for
 all encoded channels, i.e. if you select 'br 128000' and 'stereo', both
 channels will be stuffed into one bit stream of 128000 bits/second.
 Currently only ISO bit rates are accepted by the encoder. Valid bit rates
 are:

 32k  40k  48k  56k  64k  80k  96k  112k  128k  160k  192k  224k  256k  320k

 The default bitrate is 128000 bits/sec.

 Version 1.00 of the encoder is restricted to stereo bit rates greater
 than 64 kBit/s and to mono bit rates less than 320 kBit/s.

1.6 crc check
 If '-crc' is asserted, ISO/MPEG1 crc checking is enabled. Without the 'crc'
 switch, crc checking is disabled.

1.7 swap low and high byte of input samples
 If the '-tfs' option is specified, the low and high bytes of each audio
 data input sample are swapped. Use '-tfs' if you move your PCM audio data
 from little endian to big endian machines (or vice versa).

1.8 examples of switch settings
    L3ENC infile.pcm out.bit -br 112000 -cr
    L3ENC c:\music\pcm\newage.pcm c:\bitstr\l3\newage.bit -mod 2 -br 64000
    L3ENC pop.wav -wav -br 96000


2. DECODER
   =======

 L3DEC.EXE is an ISO/MPEG Layer 3 software only decoder. It takes
 Layer 3 bit stream files as input and delivers PCM audio data files
 as output. A number of options can be selected via command line
 switches. Usage:

    l3dec <bit_stream> [<PCM_audio_data>] [-switch1 [switch2 [...]]]

 L3DEC.EXE should work on any IBM PC compatible computer with a 386 CPU
 or better with external or built in 387 hardware floating point support.

 If you specify no output file name, the bit stream is nevertheless
 (partially) decoded but PCM audio output is discarded. This option is
 only useful, if you want to check the correct format of a a bit stream
 file without actually producing any output. And yes --- this is much
 faster than the full decoding process.

2.1 bit stream input file
 The format of the bit stream input file must comply with ISO/IEC
 IS11172-3. Currently there is no default file name extension.

 The decoder will process all valid MPEG1 Layer3 bit stream data
 without restrictions to bit rate or sampling frequency.

2.2 PCM audio data output file
 Audio data is output as samples of 16 bit signed integer PCM data.
 The default format is raw PCM data and can be either one channel or
 two interleaved channels.
    format of one (mono) channel PCM audio data:
        <sample #1><sample #2>....
    format of two channel (stereo) PCM audio data:
        <spl.#1 ch.#1><spl.#1 ch.#2><sp.#2 ch.#1><spl.#2 ch.#2>...
 If one or two audio channels are used depends on the encoded information in
 the bit stream. For stereo output data the first channel is the left
 channel. Information about sampling frequency and number of used channels
 is displayed at the beginning of the decoding process.

2.3 RIFF/WAVE format
 If selected by the '-wav' switch, audio data is output in RIFF/WAVE format
 (*.WAV) as used by Microsoft Windows. The audio data itself is still
 written as 16 bit PCM data as described in 2.2 but it is preceded by a
 WAVE-header. The WAVE-Header contains information about the number of
 channels (1 or 2), sampling frequency (32k/44.1k/48k) and used bits per
 sample (16).

2.4 [Sound Header]
 If selected by the '-snd' switch, audio data files are output in
  [description of audio format]

2.5 skip frames
 With the '-fb' option you can skip a number of frames in the bit stream
 before the decoding starts. '-fb nnn' skips the first nnn frames. Each
 frame contains 1152 samples of audio data. Depending on the used sampling
 frequency, the duration of a frame is calculated as 24 msec (@ 48kHz), 26.1
 msec (@ 44.1kHz) or 36 msec (@ 32kHz).

2.6 decode only nnn frames
 If you want to decode only a certain number of frames, specify the '-fn'
 option. '-fn xxx' will decode only xxx frames (see also 2.5).

2.7 search again after loss of synchronisation
 Normally the decoding process is stopped, if a loss of synchronisation is
 detected, i.e. the synch information is incorrect. To enable decoding of
 partially damaged bit stream files, you may assert the '-sa' option. In
 this mode the decoding is not stopped and the file is searched for valid
 synch information until end of file is encountered.

2.8 write audio data as ascii hex 24bit output file
 If the option '-h24 xxx' is specified an (additional) output file with
 name 'xxx' is opened. PCM Audio data is output as 24 bit ascii hex values
 followed by carriage return and line feed. Accuracy of the output values
 is 24 bit compared to the 16 bits raw output mode. Files output in
 'h24' format take four times the storage capacity necessary for raw
 16bit output format.

2.9 ignore error messages
 If errors in the bit stream are detected, the decoding process is normally
 halted. If the '-ign' option is specified, the decoder tries to continue
 with the decoding process.

2.10 accept free format bitstream
 If the '-ff' option is specified, a free format bitstream is accepted.

2.11 ancillary data
 If the bit stream contains ancillary data (user data integrated into
 the bit stream) the decoder can write this data into an ancillary
 data file. Ancillary data will be supported in a future version of the
 encoder.


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