Operate the wave file (2): Determine whether a file is a wave file

The first 12 bytes of the wave file can be described as follows:

Triff = record ckid: DWORD; {'riff'} cksize: DWORD; {file size, excluding the first 8 bytes} fcctype: DWORD; {'wave '} end;
 

We can read the first 12 bytes of a file to determine whether it is a wave file.

Uses mmsystem, ioutils; {ioutils is used here. tfile. openread easily creates a file stream} procedure tform1.formcreate (Sender: tobject); var Riff: Record ckid, cksize, fcctype: DWORD; end; {You can define the structure and declare the structure variable} begin with tfile. openread ('C: \ windows \ media \ Windows XP start .wav ') Do begin read (riff, sizeof (riff); free; end; If (riff. ckid = fourcc_riff) and (riff. fcctype = mmiostringtofourcc ('wave ', 0) Then showmessagefmt ('this is a wave file, and its size is % d byte', [riff. cksize + 8]); end;
 

Write it as a function. It is better not to reference the mmsystem unit.

{If it is a wave file, the file size is returned. If not, the system returns 0} function iswave (filepath: string): integer; function mmiofourcc (chr0, chr1, chr2, chr3: ansichar ): DWORD; begin result: = DWORD (chr0) + DWORD (chr1) SHL 8 + DWORD (chr2) SHL 16 + DWORD (chr3) SHL 24; end; var Riff: Record ckid, cksize, fcctype: DWORD; end; begin result: = 0; with tfilestream. create (filepath, fmopenread) Do begin read (riff, sizeof (riff); free; end; If (riff. ckid = mmiofourcc ('R', 'I', 'F', 'F') and (riff. fcctype = mmiofourcc ('w', 'A', 'V', 'E') then result: = riff. cksize + 8; end;
 

In turn, you can also determine the specific format of a riff file.

{A function in the riff file format is returned. If it is not a riff file, 'noniff '} function getrifftype (filepath: string): string; function mmiofourcc (chr0, chr1, chr2, chr3: ansichar): DWORD; begin result: = DWORD (chr0) + DWORD (chr1) SHL 8 + DWORD (chr2) SHL 16 + DWORD (chr3) SHL 24; end; var Riff: record ckid, cksize, fcctype: DWORD; end; Type tchars = array [0 .. 3] of ansichar; {used for type conversion} begin result: = 'noniff '; with tfilestream. create (filepath, fmopenread) Do begin read (riff, sizeof (riff); free; end; If (riff. ckid = mmiofourcc ('R', 'I', 'F', 'F') then result: = tchars (riff. fcctype); end; // test: Begin showmessage (getrifftype ('C: \ windows \ media \ Windows XP start .wav '); {wave} showmessage (getrifftype ('C: \ windows \ clock. avi '); {Avi} showmessage (getrifftype ('C: \ windows \ notepad.exe'); {noneriff} end;
 

About fourcc_riff, mmiofourcc, and mmiostringtofourcc:

Riff files are composed of several "blocks", each of which starts with four characters (less than four characters are supplemented by spaces );
The four consecutive bytes are exactly the size of a 32-bit integer, so they are often read as an integer to judge.

You can use mmsystem. mmiostringtofourcc to obtain such an integer.

From C/C ++ code, we often see that mmiofourcc is not a function in the winmm. dll library, but a macro defined in C/C ++.
Here, we use Delphi to simulate and implement this function. Its function is similar to mmiostringtofourcc.

Mmsystem. fourcc_riff is a constant. It is used directly when an integer corresponding to "riff" is required. For example:

Uses mmsystem; {custom mmiofourcc function} function mmiofourcc (chr0, chr1, chr2, chr3: ansichar): DWORD; begin result: = DWORD (chr0) + DWORD (chr1) SHL 8 + DWORD (chr2) SHL 16 + DWORD (chr3) SHL 24; end; Procedure tform1.formcreate (Sender: tobject); var F1, F2, F3, F4: fourcc; {fourcc = DWORD;} begin F1: = mmiostringtofourcc ('riff', 0); F2: = mmiostringtofourcc ('riff', mmio_toupper ); {The second parameter can be used to convert the string to uppercase.} F3: = mmiofourcc ('R', 'I', 'F', 'F'); F4: = fourcc_riff; showmessagefmt ('% d, % d', [F1, F2, F3, F4]); {1179011410,117 9011410, 1179011410,117 9011410} end;