好久没写BLOG了，送上一份原创的DELPHI版MP3切割，splitMp3为切割函数，支持按时间切割和按大小切割。望大家支持。

参考VC的资料编写的MP3切割DELPHI版单元.

unit UnitMp3DataUtil;

{

MP3 Cut Unit.

@author Jim Wu

2009-08

}

interface

uses

Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls;

type

Mp3SplitMode = (Mp3SplitByTime, Mp3SplitByDateLength);

TMp3DataInfo = packed record

isMp3: Boolean;

bitrate: Integer;

sampleRate: Integer;

isMono: Boolean;

isVBR: Boolean;

end;

function readMp3Head(fileName: string): TMp3DataInfo;

function splitMp3(mode: Mp3SplitMode; length: Integer; fr: TFileStream; writeFileName: string; var actualLength: Integer; var actualMillisecond: Integer): integer;

const

mpegBitrateTable: array[1..2,1..3,1..14] of Integer=(

(

( 32, 64, 96,128,160,192,224,256,288,320,352,384,416,448),

( 32, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,384),

( 32, 40, 48, 56, 64, 80, 96,112,128,160,192,224,256,320)

),

(

( 32, 48, 56, 64, 80, 96,112,128,144,160,176,192,224,256),

(  8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160),

(  8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160)

)

);

samplingRateTable: array[1..3,0..2] of Integer=(

(44100,48000,32000),

(22050,24000,16000),

(11025,12000,8000)

);

frameLengthTable: array[1..2,1..3] of Integer=(

(48000,144000,144000),

(24000, 72000, 72000)

);

samplesPerFrameTable: array[1..2,1..3] of Integer=(

( 384,1152,1152),

( 384,1152, 576)

);

implementation

function readMp3Head(fileName: string): TMp3DataInfo;

var

binData: array [0..3] of Byte;

tempDate: array [0..3] of Byte;

fr: TFileStream;

mpegPadding: Byte;

mpegVersion: Double;

mpegLayer: Byte;

seekDataLength: Integer;

begin

fr := TFileStream.Create(fileName, fmOpenRead);

fr.Read(binData, 4);

if (binData[0] = $49) and (binData[1] = $44) and (binData[2] = $33) then

begin //readMp3Head

fr.Seek(2, soFromCurrent);

fr.Read(tempDate, 4); //解析长度

seekDataLength := tempDate[0] and $7F shl 21 + tempDate[1] and $7F shl 14 + tempDate[2] and $7F shl 7 + tempDate[3] and $7F;

fr.Seek(seekDataLength, soFromCurrent);

fr.Read(binData, 4);

end;

if binData[0] = $FF then //DATA Frame

begin

case binData[1] shr 3 and $3 of

0: mpegVersion := 2.5;

1: ; //reserved

2: mpegVersion := 2;

3: mpegVersion := 1;

end;

mpegLayer := 4 - (binData[1] shr 1 and $3);

result.bitrate := mpegBitrateTable[Trunc(mpegVersion)][mpegLayer][binData[2] shr 4 and $F];

result.sampleRate := samplingRateTable[Trunc(mpegVersion+0.5)][binData[2] shr 2 and $3];

mpegPadding := binData[2] shr 1 and $1;

if binData[3] shr 6 and $3 = 3 then

result.isMono := True

else

Result.isMono := False;

fr.Seek(32, soFromCurrent); //read Xing(VBR) Flag

fr.Read(tempDate, 4);

if (tempDate[0] = $58) and (tempDate[1] = $69) and (tempDate[2] = $6E) and (tempDate[3] = $67) then

Result.isVBR := True

else

Result.isVBR := False;

Result.isMp3 := True;

end

else

Result.isMp3 := False; //not MP3 file

fr.Free;

end;

function processFrame(fr: TFileStream; fw: TFileStream; var writeLength: Integer; var writeMillisecond: double): LongInt; //返回：文件位置

var

binData: array [0..3] of Byte;

seekDataLength: Integer;

mpegPadding: Byte;

mpegVersion: Double;

mpegLayer: Byte;

mpegBitrate: Integer;

mpegSamplingRate : Integer;

trackMode: Integer;

begin

fr.Read(binData, 4);

if (binData[0] = $49) and (binData[1] = $44) and (binData[2] = $33) then

begin //IDV3

fr.Seek(2, soFromCurrent);

fr.Read(binData, 4); //解析长度

seekDataLength := binData[0] and $7F shl 21 + binData[1] and $7F shl 14 + binData[2] and $7F shl 7 + binData[3] and $7F;

fr.Seek(seekDataLength, soFromCurrent); //instead of write

writeLength := 0;

writeMillisecond := 0;

end

else

if binData[0] = $FF then //DATA Frame

begin

case binData[1] shr 3 and $3 of

0: mpegVersion := 2.5;

1: ; //reserved

2: mpegVersion := 2;

3: mpegVersion := 1;

end;

mpegLayer := 4 - (binData[1] shr 1 and $3);

mpegBitrate := mpegBitrateTable[Trunc(mpegVersion)][mpegLayer][binData[2] shr 4 and $F];

mpegSamplingRate  := samplingRateTable[Trunc(mpegVersion+0.5)][binData[2] shr 2 and $3];

mpegPadding := binData[2] shr 1 and $1;

seekDataLength := Trunc((samplesPerFrameTable[Trunc(mpegVersion)][mpegLayer] / 8 * mpegBitrate * 1000) / mpegSamplingRate) + mpegPadding;

fr.Seek(32, soFromCurrent); //read Xing(VBR) Flag

fr.Read(binData, 4);

if (binData[0] = $58) and (binData[1] = $69) and (binData[2] = $6E) and (binData[3] = $67) then

begin

fr.Seek(seekDataLength - 4 - 32 - 4, soFromCurrent);

result := fr.Position;

writeLength := 0;

writeMillisecond := 0;

end

else //writeData

begin

fr.Seek(-32 - 4 - 4, soFromCurrent);

fw.CopyFrom(fr, seekDataLength); //copy a frame

writeLength := seekDataLength;

writeMillisecond := samplesPerFrameTable[Trunc(mpegVersion)][mpegLayer] * 1000.0 / mpegSamplingRate;

result := fr.Position;

end;

end

else

begin

writeLength := 0;

writeMillisecond := 0;

result := fr.Position;

end;

end;

function splitMp3(mode: Mp3SplitMode; length: Integer; fr: TFileStream; writeFileName: string; var actualLength: Integer; var actualMillisecond: Integer): integer;

//length:限制，对于SplitByTime，为毫秒，对于长度，为byte

//actualLength为实际切分长度，actualTime为实际切分毫秒

var

writeLength: Integer;

writeMillisecond: double;

tempMillisecond: double;

fw: TFileStream;

total: double;

begin

fw := TFileStream.Create(writeFileName, fmOpenWrite or fmCreate);

total := 0;

actualLength := 0;

tempMillisecond := 0;

while True do

begin

if fr.Position >= fr.Size - 4 then

break;

if total >= length then

break;

result := processFrame(fr, fw, writeLength, writeMillisecond);

Inc(actualLength, writeLength);

tempMillisecond := tempMillisecond + writeMillisecond;

if mode = Mp3SplitByTime then

total := total + writeMillisecond

else

total := total + writeLength;

end;

actualMillisecond := Trunc(tempMillisecond);

fw.Free;

end;

end.