%%?MP3?reading?and?writing
%
%?These?function?mp3read?and?mp3write?aim?to?exactly?duplicate?
%?the?operation?of?wavread?and?wavwrite?for?accessing?soundfiles?
%?except?the?soundfiles?are?in?Mpeg-Audio?layer?3?（MP3）?compressed?
%?format.??All?the?hard?work?is?done?by?external?binaries?written?
%?by?others:?mp3info?to?query?the?format?of?existing?mp3?files?
%?mpg123?to?decode?mp3?files?and?lame?to?encode?audio?files.
%?Binaries?for?these?files?are?widely?available?（and?may?be
%?included?in?this?distribution）.??
%
%?These?functions?were?originally?developed?for?access?to?very?
%?large?mp3?files?（i.e.?many?hours?long）?and?so?avoid?creating?
%?the?entire?uncompressed?audio?stream?if?possible.??mp3read?
%?allows?you?to?specify?the?range?of?frames?you?want?to?read?
%?（as?a?second?argument）?and?mp3read?will?construct?an?mpg123?
%?command?that?skips?blocks?to?decode?only?the?part?of?the?file?
%?that?is?required.??This?can?be?much?quicker?（and?require?less?
%?memory/temporary?disk）?than?decoding?the?whole?file.
%
%?mpg123?also?provides?for?“on?the?fly“?downsampling?at?conversion?
%?to?mono?which?are?supported?as?extra?options?in?mp3read.
%
%?For?more?information?including?advice?on?handling?MP4?files?
%?see?http://labrosa.ee.columbia.edu/matlab/mp3read.html

%%?Example?usage
%?Here?we?read?a?wav?file?in?then?write?it?out?as?an?MP3?then?
%?read?the?resulting?MP3?back?in?and?compare?it?to?the?original?
%?file.

%?Read?an?audio?waveform
[dsr]?=?wavread（‘piano.wav‘）;
%?Save?to?mp3?（default?settings）
mp3write（dsr‘piano.mp3‘）;
%?Read?it?back?again
[d2sr]?=?mp3read（‘piano.mp3‘）;
%?mp3?encoding?involves?some?extra?padding?at?each?end;?we?attempt?
%?to?cut?it?off?at?the?start?but?can‘t?do?that?at?the?end?because?
%?mp3read?doesn‘t?know?how?long?the?original?was.??But?we?do?so..
%?Chop?it?down?to?be?the?same?length?as?the?original
d2?=?d2（1:length（d）:）;
%?What?is?the?SNR?（distortion）?
ddiff?=?d?-?d2;
disp（[‘SNR?is?‘num2str（10*log10（sum（d（:）.^2）/sum（ddiff（:）.^2）））‘?dB‘]）;
%?Do?they?look?similar?
subplot（211）
specgram（d（:1）1024sr）;
subplot（212）
plot（1:5000d（10000+（1:5000）1）1:5000d2（10000+（1:5000）））;
%?Yes?pretty?close
%
%?NB:?lame?followed?by?mpg123?causes?a?little?attenuation;?you?
%?can?get?a?better?match?by?scaling?up?the?read-back?waveform:
ddiff?=?d?-?1.052*d2;
disp（[‘SNR?is?‘num2str（10*log10（sum（d（:）.^2）/sum（ddiff（:）.^2）））‘?dB‘]）;

%%?External?binaries
%?The?m?files?rely?on?three?external?binaries?each?of?which?is
%?available?for?Linux?Mac?OS?X?or?Windows:
%
%?*mpg123*?is?a?high-performance?mp3?decoder.??Its?home?page?is
%?http://www.mpg123.de/?.??
%
%?*mp3info*?is?a?utility?to?read?technical?information?on?an?mp3
%?file.?Its?home?page?is?http://www.ibiblio.org/mp3info/?.??
%
%?*lame*?is?an?open-source?MP3?encoder.??Its?homepage?is
%?http://lame.sourceforge.net/?.
%
%?The?various?authors?of?these?packages?are?gratefully?acknowledged?
%?for?doing?all?the?hard?work?to?make?these?Matlab?functions?possible.

%%?Installation
%?The

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2007-07-30?15:37??__MACOSX\
?????目錄???????????0??2007-07-30?15:37??__MACOSX\mp3readwrite\
?????文件??????????82??2007-03-30?17:11??__MACOSX\mp3readwrite\._.DS_Store
?????文件????????1544??2009-05-19?15:17??license.txt
?????目錄???????????0??2007-07-30?15:36??mp3readwrite\
?????文件????????6148??2007-03-30?17:11??mp3readwrite\.DS_Store
?????文件????????3728??2007-02-04?23:09??mp3readwrite\demo_mp3readwrite.m
?????目錄???????????0??2007-02-04?23:14??mp3readwrite\html\
?????文件???????10834??2007-02-04?23:14??mp3readwrite\html\demo_mp3readwrite.html
?????文件????????6212??2007-02-04?23:14??mp3readwrite\html\demo_mp3readwrite.png
?????文件???????63096??2007-02-04?23:14??mp3readwrite\html\demo_mp3readwrite_01.png
?????文件??????195072??2002-04-16?13:35??mp3readwrite\lame.exe
?????文件??????377484??2002-01-02?22:56??mp3readwrite\lame.glnx86
?????文件??????469376??2006-12-30?17:39??mp3readwrite\lame.mac
?????文件??????490312??2007-02-04?21:32??mp3readwrite\lame.maci
?????文件???????71680??2004-10-23?16:20??mp3readwrite\mp3info.exe
?????文件???????22896??2001-07-17?05:30??mp3readwrite\mp3info.glnx86
?????文件???????60364??2004-09-08?21:09??mp3readwrite\mp3info.mac
?????文件???????35032??2007-02-04?20:37??mp3readwrite\mp3info.maci
?????文件???????10042??2007-07-30?15:36??mp3readwrite\mp3read.m
?????文件????????4870??2007-07-26?15:09??mp3readwrite\mp3write.m
?????文件??????139264??2004-10-23?16:20??mp3readwrite\mpg123.exe
?????文件??????159824??2000-02-02?23:31??mp3readwrite\mpg123.glnx86
?????文件??????124076??2004-01-30?02:08??mp3readwrite\mpg123.mac
?????文件??????122464??2007-02-04?19:37??mp3readwrite\mpg123.maci
?????文件??????829672??2007-02-04?20:16??mp3readwrite\piano.wav