mpeg音频编码和解码

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION ISO/IEC JTC1/SC29/WG 11 CODING OF MOVING PICTURES AND ASSOCIATED AUDIO MPEG94/ Nov. 1994 Source: Davis Pan (Motorola Inc.), Chairman of the MPEG/audio ad hoc committee on software simulation Title: Working Draft of MPEG/Audio Technical Report Disclaimer of Warranty These software programs are available to the user without any license fee or royalty on an "as is" basis. ISO disclaims any and all warranties, whether express, implied, or statuary, including any implied warranties or merchantability or of fitness for a particular purpose. In no event shall ISO be liable for any incidental, punitive, or consequential damages of any kind whatsoever arising from the use of these programs. This disclaimer of warranty extends to the user of these programs and user's customers, employees, agents, transferees, successors, and assigns, ISO does not represent or warrant that the programs furnished hereunder are free of infringement or any third-party patents, copyrights or trade secrets. The purpose of this software is to provide a tool to help in the learning and understanding of the MPEG/audio compression and decompression algorithm. It is not an efficient implementation. Organization of this Report The main body of this report describes the organization and use of the software. The listings of the software, sample makefiles, and test bitstreams are contained in the appendices: Software Limitations The software implements levels I and II and psychophysical auditory models I and II as described in the ISO 3-11171 rev 1 standard. The input/output audio data may either be headerless raw 16 bit data or alternatively an AIFF formatted file (Audio Interchange File Format) with certain limitations. (For more information on the AIFF format see the postscript file /sgi/aiff-c.9.26.91.ps at the anonymous ftp site FTP.SGI.COM (192.48.153.1)). The AIFF formatted file is a convenient way for storing sampling rate of the audio file. The encoder and decoder software are configured to output the coded audio bitstreams as a string of hexadecimal ascii characters. For greater compression efficiency, compile flag, BS_FORMAT, in common.h can be switched to configure the bitstream reading and writing routines to process raw binary bitstreams. This software has been run and verified on a large variety of computers and operating systems. In particular UNIX, MS_DOS (with MicroSoft C version 6), Macintosh, AIX Platform (RS6000) and Convex. Organization of the Code The MPEG/audio Layer 1 and Layer 2 ** software package consists of: 21 data files tables 8 source files (*.c) 3 definitions files (*.h) 3 test bitstreams * makefiles ** There is a separate release note for the Layer 3 software Table 1 illustrates how the encoder and decoder is formed from the component files. In this table the definition files are enclosed in parenthesis and listed immediately below the primary source file which uses them. The data file names are listed within braces and also placed immediately below the source file which uses them. Table 1 encoder common decoder files files files ---------- ------------ ------------ musicin.c common.c musicout.c encode.c (common.h) decode.c (encoder.h) {alloc_0} (decoder.h) {enwindow} {alloc_1} {dewindow} psy.c, subs.c {alloc_2} {absthr_0} {alloc_3} {absthr_1} {absthr_2} tonal.c {1cb0}, {1cb1}, {1cb2} {2cb0}, {2cb1}, {2cb2} {1th0}, {1th1}, {1th2} {2th0}, {2th1}, {2th2} The test files orig.mpg and sine.dec are approximately 129026 and 387072 bytes. (Small variations are due to the blocking structures imposed by various disk operating systems.) Software Installation Place are the 21 tables (absthr_*, *cb*, *th*, alloc_*) in a subdirectory called tables. Modify the common.h to reflect the compiler and machine you are using. (ie. uncomment one of the defs UNIX, MACINTOSH, MS_DOS, MSC60, AIX or CONVEX). Compile and link the files using one of the makefiles provided as a guideline. Note that the compiler may issue warning messages such as common.c: In function `aiff_read_headers': common.c:686: warning: multi-character character constant common.c:687: warning: multi-character character constant common.c:703: warning: multi-character character constant common.c:735: warning: multi-character character constant common.c: In function `aiff_write_headers': common.c:825: warning: multi-character character constant common.c:826: warning: multi-character character constant common.c:827: warning: multi-character character constant musicin.c:920: warning: static declaration for `usage' follows non-static musicin.c: In function `aiff_check': musicin.c:960: warning: multi-character character constant These messages are dependent on the preprocessor directives specified in the common.h file. Usuage To run the code type the name of the file followed by a carriage return. The programs will prompt you to input the appropriate parameters. The sound input file for the encoder should be sound data, monophonic or stereophonic, sampled at 32, 44.1, or 48 kHz with 16 bits per sample. For stereophonic data the left channel sample should precede the right channel sample. The sound output file of the decoder will be the same format as the sound input file used by the decoder, except for possible byte order differences if the encoder and decoder programs are run on different computer systems which have different byte ordering conventions. Assuming the program musicin produces the MPEG coded file and musicout decodes the MPEG coded file, the programs can be run in either commandline mode or user prompt mode. For example, on a UNIX operating system, entering musicin sine.dec sine.mpg will run the program with the current built in defaults. The output from the program should appear as below. Encoding configuration: Layer=II mode=stereo extn=0 psy model=2 samp frq=44.1 kHz total bitrate=384 kbps de-emph=0 c/right=0 orig=0 errprot=0 input file: 'sine.dec' output file: 'sine.mpg' using bit allocation table alloc_1 slots/frame = 1253 frac SpF=0.878, tot bitrate=384 kbps, s freq=44.1 kHz Fractional number of slots, padding required { 0}absthr[][] sampling frequency index: 1 { 1}{ 2}{ 3}{ 4}{ 5}{ 6}{ 7}... Alternatively, if you enter musicin -help The program will respond with the correct command-line usuage as shown below and then exit. musicin: unrec option h musicin: -l layer must be 1 or 2, not p usage: musicin queries for all arguments, or musicin [-l lay][-m mode][-p psy][-s sfrq][-b br][-d emp] [-c][-o][-e] inputPCM [outBS] where -l lay use layer <lay> coding (dflt 2) -m mode channel mode : s/d/j/m (dflt s) -p psy psychoacoustic model 1/2 (dflt 2) -s sfrq input smpl rate in kHz (dflt 44.1) -b br total bitrate in kbps (dflt 384) -d emp de-emphasis n/5/c (dflt n) -c mark as copyright -o mark as original -e add error protection inputPCM input PCM sound file (standard or AIFF) outBS output bit stream of encoded audio (dflt inName+.mpg) Finally, if you just enter musicin Then the program will prompt you for all the coding parameters before executing. Enter PCM input file name <required>: sine.dec >>> PCM input file name is: sine.dec Enter MPEG encoded output file name <sine.dec.mpg>: sine.mpg >>> MPEG encoded output file name is: sine.mpg What is the sampling frequency? <44100>[Hz]: >>> Default 44.1 kHz samp freq sele