soxexam.txt

visual c++编写关于声音分析的 傅立叶变换．超牛

SoX(1)									SoX(1)



NAME
       soxexam - SoX Examples (CHEAT SHEET)

CONVERSIONS
       Introduction

       In  general,  SoX  will	attempt to take an input sound file format and
       convert it into a new file format using a similar data type and	sample
       rate.   For  instance, "sox monkey.au monkey.wav" would try and convert
       the mono 8000Hz u-law sample .au file that comes with SoX to  a	8000Hz
       u-law .wav file.

       If  an  output  format  doesn’t support the same data type as the input
       file then SoX will generally select a default data type to save it  in.
       You  can override the default data type selection by using command line
       options.	 This is also useful for producing an output file with	higher
       or lower precision data and/or sample rate.

       Most  file  formats  that contain headers can automatically be read in.
       When working with header-less file formats then a  user	must  manually
       tell SoX the data type and sample rate using command line options.

       When working with header-less files (raw files), you may take advantage
       of the pseudo-file types of .ub, .uw, .sb, .sw, .ul, and .sl.  By using
       these  extensions  on  your  filenames you will not have to specify the
       corresponding options on the command line.

       Precision

       The following data types and formats can be represented by their	 total
       uncompressed  bit  precision.   When  converting	 from one data type to
       another care must be taken to insure it has an equal or greater	preci-
       sion.   If  not	then  the audio quality will be degraded.  This is not
       always a bad thing when your working with things such  as  voice	 audio
       and are concerned about disk space or bandwidth of the audio data.

	       Data Format    Precision
	       ___________    _________
	       unsigned byte	8-bit
	       signed byte	8-bit
	       u-law	       14-bit
	       A-law	       13-bit
	       unsigned word   16-bit
	       signed word     16-bit
	       ADPCM	       16-bit
	       GSM	       16-bit
	       unsigned long   32-bit
	       signed long     32-bit
	       ___________    _________

       Examples

       Use  the ’-V’ option on all your command lines.	It makes SoX print out
       its idea of what is going on.  ’-V’ is your friend.

       To convert from unsigned bytes at 8000 Hz to signed words at 8000 Hz:

	 sox -r 8000 -c 1 filename.ub newfile.sw

       To convert from Apple’s AIFF format to Microsoft’s WAV format:

	 sox filename.aiff filename.wav

       To convert from mono raw 8000 Hz 8-bit unsigned PCM data to a WAV file:

	 sox -r 8000 -u -b -c 1 filename.raw filename.wav

       SoX  may	 even  be  used	 to convert sample rates.  Downconverting will
       reduce the bandwidth of a sample, but will reduce storage space on your
       disk.   All  such  conversions are lossy and will introduce some noise.
       You should really pass your sample through a low pass filter  prior  to
       downconverting  as  this	 will prevent alias signals (which would sound
       like additional noise).	For example to convert from a sample  recorded
       at 11025 Hz to a u-law file at 8000 Hz sample rate:

	 sox infile.wav -t au -r 8000 -U -b -c 1 outputfile.au

       To  add	a  low-pass filter (note use of stdout for output of the first
       stage and stdin for input on the second stage):

	 sox infile.wav -t raw -s -w -c 1 - lowpass 3700  |
	   sox -t raw -r 11025 -s -w -c 1 - -t au -r 8000 -U -b -c 1 ofile.au

       If you hear some clicks and pops when converting	 to  u-law  or	A-law,
       reduce  the output level slightly, for example this will decrease it by
       20%:

	 sox infile.wav -t au -r 8000 -U -b -c 1 -v .8 outputfile.au


       SoX is great to use along with other command line programs  by  passing
       data  between the programs using pipelines.  The most common example is
       to use mpg123 to convert mp3 files in to wav files.  The following com-
       mand line will do this:

	 mpg123	 -b  10000  -s filename.mp3 | sox -t raw -r 44100 -s -w -c 2 -
       filename.wav

       When working with totally unknown audio data then the "auto" file  for-
       mat may be of use.  It attempts to guess what the file type is and then
       you may save it into a known audio format.

	 sox -V -t auto filename.snd filename.wav

       It is important to understand how the internals of SoX work  with  com-
       pressed	audio  including  u-law,  A-law, ADPCM, or GSM.	 SoX takes ALL
       input data types and converts them to uncompressed 32-bit signed	 data.
       It  will	 then  convert this internal version into the requested output
       format.	This means additional noise can be introduced from decompress-
       ing data and then recompressing.	 If applying multiple effects to audio
       data, it is best to save the intermediate data as PCM data.  After  the
       final effect is performed, then you can specify it as a compressed out-
       put format.  This will keep noise introduction to a minimum.

       The following example applies various effects to an 8000 Hz ADPCM input
       file and then end up with the final file as 44100 Hz ADPCM.

	 sox firstfile.wav -r 44100 -s -w secondfile.wav
	 sox secondfile.wav thirdfile.wav swap
	 sox thirdfile.wav -a -b finalfile.wav mask

       Under a DOS shell, you can convert several audio files to an new output
       format using something similar to the following command line:

	 FOR %X IN (*.RAW) DO sox -r 11025 -w -s -t raw $X $X.wav

EFFECTS
       Special thanks goes to Juergen Mueller ([e-mail]) for this
       write up on effects.

       Introduction:

       The  core  problem is that you need some experience in using effects in
       order to say "that any old sound file sounds  with  effects  absolutely
       hip". There isn’t any rule-based system which tell you the correct set-
       ting of all the parameters for every effect.  But after some  time  you
       will become an expert in using effects.

       Here are some examples which can be used with any music sample.	(For a
       sample where only a single instrument  is  playing,  extreme  parameter
       setting	may  make  well-known "typically" or "classical" sounds. Like-
       wise, for drums, vocals or guitars.)

       Single effects will be explained and some given parameter settings that
       can  be	used  to  understand the theory by listening to the sound file
       with the added effect.

       Using multiple effects in parallel or in series can result either in  a
       very  nice sound or (mostly) in a dramatic overloading in variations of
       sounds such that your ear may follow the sound but you will feel unsat-
       isfied.	Hence, for the first time using effects try to compose them as
       minimally as possible. We don’t regard the composition  of  effects  in
       the  examples because too many combinations are possible and you really
       need a very fast machine and a lot of memory to play them in real-time.

       However,	 real-time  playing  of	 sounds will greatly speed up learning
       and/or tuning the parameter settings for your sounds in	order  to  get
       that "perfect" effect.

       Basically,  we  will use the "play" front-end of SoX since it is easier
       to listen sounds coming out of the speaker or earphone instead of look-
       ing at cryptic data in sound files.

       For easy listening of file.xxx ("xxx" is any sound format):

	     play file.xxx effect-name effect-parameters

       Or more SoX-like (for "dsp" output on a UNIX/Linux computer):

	      sox file.xxx -t ossdsp -w -s /dev/dsp effect-name effect-parame-
       ters

       or (for "au" output):

	     sox file.xxx -t sunau -w -s /dev/audio effect-name effect-parame-
       ters

       And for date freaks:

	     sox file.xxx file.yyy effect-name effect-parameters

       Additional  options  can	 be used. However, in this case, for real-time
       playing you’ll need a very fast machine.

       Notes:

       I played all examples in real-time on a Pentium	100  with  32  MB  and
       Linux 2.0.30 using a self-recorded sample ( 3:15 min long in "wav" for-
       mat with 44.1 kHz sample rate and stereo 16 bit ).  The	sample	should
       not contain any of the effects. However, if you take any recording of a
       sound track from radio or tape or CD, and it sounds like a live concert
       or  ten	people	are playing the same rhythm with their drums or funky-
       grooves, then take any other sample.  (Typically, less then  four  dif-
       ferent  instruments and no synthesizer in the sample is suitable. Like-
       wise, the combination vocal, drums, bass and guitar.)

       Effects:

       Echo

       An echo effect can be naturally found in the mountains, standing	 some-
       where  on  a  mountain and shouting a single word will result in one or
       more repetitions of the word (if not, turn a bit around and try	again,
       or climb to the next mountain).

       However,	 the  time  difference	between	 shouting and repeating is the
       delay (time), its loudness is the decay. Multiple echos can  have  dif-
       ferent delays and decays.

       It  is  very  popular  to  use  echos to play an instrument with itself
       together, like some guitar players (Brain May from Queen) or  vocalists
       are  doing.  For music samples of more than one instrument, echo can be
       used to add a second sample shortly after the original one.

       This will sound as if you are doubling the number of instruments	 play-
       ing in the same sample:

	     play file.xxx echo 0.8 0.88 60.0 0.4

       If the delay is very short, then it sound like a (metallic) robot play-
       ing music:

	     play file.xxx echo 0.8 0.88 6.0 0.4

       Longer delay will sound like an open air concert in the mountains:

	     play file.xxx echo 0.8 0.9 1000.0 0.3

       One mountain more, and:

	     play file.xxx echo 0.8 0.9 1000.0 0.3 1800.0 0.25

       Echos

       Like the echo effect, echos stand for "ECHO in  Sequel",	 that  is  the
       first  echos takes the input, the second the input and the first echos,
       the third the input and the first and the second echos, ... and so  on.
       Care  should  be	 taken	using  many echos (see introduction); a single
       echos has the same effect as a single echo.

       The sample will be bounced twice in symmetric echos:

	     play file.xxx echos 0.8 0.7 700.0 0.25 700.0 0.3