pass mp3 file through program

[tripper]

The attached code takes and mp3 file and converts it from 16bits to 8eight bits as well sends the PCM through the serial port. I was able to compile it in MSVC 6, but I am having difficulty loading an mp3 file. I tried loading an mp3 file with the following line:

#include <windows.h>
#include <stdio.h>
#include <assert.h>
#include <mmreg.h>
#include <msacm.h>
#pragma comment (lib, "msacm32.lib")


#define MP3_BLOCK_SIZE 522
#define SOURCE_MP3 "sound.mp3";
//#define output.pcm "c:\\dump.pcm"
HANDLE hComm;

void OpenComm()
{
  DCB dcb;

  hComm = CreateFile("COM1:", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
  if(hComm==INVALID_HANDLE_VALUE) exit(1);

  if(!SetupComm(hComm, 4096, 4096)) exit(1);
  
  if(!GetCommState(hComm, &dcb)) exit(1);
  dcb.BaudRate = 115200;
  dcb.ByteSize = 8;
  dcb.Parity = NOPARITY;
  dcb.StopBits = 0;
  if(!SetCommState(hComm, &dcb)) exit(1);
}

void CloseComm()
{
  CloseHandle(hComm);
}

DWORD WriteComm(BYTE* buf, int len)
{
  DWORD nSend;
  if(!WriteFile(hComm, buf, len, &nSend, NULL)) exit(1);

  return nSend;
} 

////////////////////////////////////////////////////////////
typedef struct mpeglayer3waveformat_tag1
{
 WAVEFORMATEX  wfx;
WORD          wID;
DWORD         fdwFlags;
WORD          nBlockSize;
WORD          nFramesPerBlock;
WORD          nCodecDelay;
} MPEGLAYER3WAVEFORMAT1;

typedef MPEGLAYER3WAVEFORMAT FAR  *LPMPEGLAYER3WAVEFORMAT;
#define MPEGLAYER3_WFX_EXTRA_BYTES   12
#define WAVE_FORMAT_MPEGLAYER3  0x0055

#define MPEGLAYER3_ID_UNKNOWN            0
#define MPEGLAYER3_ID_MPEG               1
#define MPEGLAYER3_ID_CONSTANTFRAMESIZE  2

#define MPEGLAYER3_FLAG_PADDING_ISO      0x00000000
#define MPEGLAYER3_FLAG_PADDING_ON       0x00000001
#define MPEGLAYER3_FLAG_PADDING_OFF      0x00000002

////////////////////////////////////////////////////////////
HACMSTREAM g_mp3stream = NULL;
typedef SHORT* LPSHORT;

BYTE PCM[0x200000];  // 2MB reserved for the decoded PCM
int iPCM = 0;

int DecodeMP3(char* SOURCE_MP3)
{
  MMRESULT mmr;

  // find the biggest format size
  DWORD maxFormatSize = 0;
  mmr = acmMetrics(NULL, ACM_METRIC_MAX_SIZE_FORMAT, &maxFormatSize);
  
  // define desired output format
  LPWAVEFORMATEX waveFormat = (LPWAVEFORMATEX) LocalAlloc(LPTR, maxFormatSize);
  waveFormat->wFormatTag = WAVE_FORMAT_PCM;
  waveFormat->nChannels = 2; // stereo
  waveFormat->nSamplesPerSec = 44100; // 44.1kHz
  waveFormat->wBitsPerSample = 16; // 16 bits
  waveFormat->nBlockAlign = 4; // 4 bytes of data at a time are useful (1 sample)
  waveFormat->nAvgBytesPerSec = 4 * 44100; // byte-rate
  waveFormat->cbSize = 0; // no more data to follow
  
  // define MP3 input format
  LPMPEGLAYER3WAVEFORMAT mp3format = (LPMPEGLAYER3WAVEFORMAT) LocalAlloc(LPTR, maxFormatSize);
  mp3format->wfx.cbSize = MPEGLAYER3_WFX_EXTRA_BYTES;
  mp3format->wfx.wFormatTag = WAVE_FORMAT_MPEGLAYER3;
  mp3format->wfx.nChannels = 2;
  mp3format->wfx.nAvgBytesPerSec = 128 * (1024 / 8);  // not really used but must be one of 64, 96, 112, 128, 160kbps
  mp3format->wfx.wBitsPerSample = 0;                  // MUST BE ZERO
  mp3format->wfx.nBlockAlign = 1;                     // MUST BE ONE
  mp3format->wfx.nSamplesPerSec = 44100;              // 44.1kHz
  mp3format->fdwFlags = MPEGLAYER3_FLAG_PADDING_OFF;
  mp3format->nBlockSize = MP3_BLOCK_SIZE;             // voodoo value #1
  mp3format->nFramesPerBlock = 1;                     // MUST BE ONE
  mp3format->nCodecDelay = 1393;                      // voodoo value #2
  mp3format->wID = MPEGLAYER3_ID_MPEG;
  
  g_mp3stream = NULL;
  mmr = acmStreamOpen(&g_mp3stream,     // open an ACM conversion stream
  		     NULL,                       // querying all ACM drivers
  		     (LPWAVEFORMATEX) mp3format, // converting from MP3
  		     waveFormat,                 // to WAV
  		     NULL,                       // with no filter
  		     0,                          // or async callbacks
  		     0,                          // (and no data for the callback)
  		     0                           // and no flags
  		    );
  
  LocalFree(mp3format);
  LocalFree(waveFormat);
  
  switch(mmr ) {
   case MMSYSERR_NOERROR:
     break; // success!
   case MMSYSERR_INVALPARAM:
     assert(!"Invalid parameters passed to acmStreamOpen");
     return E_FAIL;
   case ACMERR_NOTPOSSIBLE:
     assert(!"No ACM filter found capable of decoding MP3");
     return E_FAIL;
   default:
     assert(!"Some error opening ACM decoding stream!");
     return E_FAIL;
  }
  
  // MP3 stream converter opened correctly
  // now, let's open a file, read in a bunch of MP3 data, and convert it!
  
  // open file

  FILE *fpIn = fopen(SOURCE_MP3,"rb");
  if(fpIn == NULL )
  {
    assert(!"can't open MP3 file!");
    return E_FAIL;
  }
  
  // find out how big the decompressed buffer will be
  unsigned long rawbufsize = 0;
  mmr = acmStreamSize(g_mp3stream, MP3_BLOCK_SIZE, &rawbufsize, ACM_STREAMSIZEF_SOURCE);
  assert(mmr == 0);
  assert(rawbufsize > 0);
  
  // allocate our I/O buffers
  LPBYTE mp3buf = (LPBYTE) LocalAlloc(LPTR, MP3_BLOCK_SIZE);
  LPBYTE rawbuf = (LPBYTE) LocalAlloc(LPTR, rawbufsize);
  
  // prepare the decoder
  ACMSTREAMHEADER mp3streamHead;
  ZeroMemory(&mp3streamHead, sizeof(ACMSTREAMHEADER ));
  mp3streamHead.cbStruct = sizeof(ACMSTREAMHEADER);
  mp3streamHead.pbSrc = mp3buf;
  mp3streamHead.cbSrcLength = MP3_BLOCK_SIZE;
  mp3streamHead.pbDst = rawbuf;
  mp3streamHead.cbDstLength = rawbufsize;
  mmr = acmStreamPrepareHeader(g_mp3stream, &mp3streamHead, 0);
  assert(mmr == 0);
  
//FILE *fpOut = fopen("output.pcm", "wb"); if(fpOut == NULL ){assert(!"can't output output PCM!");return E_FAIL;}

  while(1)
  {
    // suck in some MP3 data
    DWORD count = fread(mp3buf, 1, MP3_BLOCK_SIZE, fpIn);
    if(count != MP3_BLOCK_SIZE ) break;
  
    // convert the data
    mmr = acmStreamConvert(g_mp3stream, &mp3streamHead, ACM_STREAMCONVERTF_BLOCKALIGN);
    assert(mmr == 0);
  
	// convert 16-bits 44KHz stereo to 8-bits 11KHz mono
	int newbuflength = mp3streamHead.cbDstLengthUsed/16;
	LPSHORT shortbuf = (LPSHORT)rawbuf;

	for(int i=0; i<newbuflength; i++)
	{
		int acc = 0;
		for(int j=0; j<8; j++) acc += *shortbuf++;
//		rawbuf[i] = acc/256/8 + 0x80;
		if(iPCM<sizeof(PCM))  PCM[iPCM++] = acc/256/8 + 0x80;
	}
	if(iPCM>=sizeof(PCM)) break;

	// send to serial port
//	WriteComm(rawbuf, newbuflength);
//	printf(".");

    // write the decoded PCM to disk
//    count = fwrite(rawbuf, 1, newbuflength, fpOut);
  };
  
  fclose(fpIn);
//fclose(fpOut);

  mmr = acmStreamUnprepareHeader(g_mp3stream, &mp3streamHead, 0);
  assert(mmr == 0);
  LocalFree(rawbuf);
  LocalFree(mp3buf);
  mmr = acmStreamClose(g_mp3stream, 0);
  assert(mmr == 0);
  
  return S_OK;
}

int main(int argc, char *argv[])
{
	if(argc!=2)
	{
		printf("argument required (mp3 file)!\n");
		exit(1);
	}

	printf("Playing %s\n", argv[1]);

	OpenComm();
	printf("decoding... ");	DecodeMP3(argv[1]);
	printf("playing... ");	WriteComm(PCM, iPCM);
	CloseComm();
	return 0;
}

#define SOURCE_MP3 "song.mp3"

but this returns several compiling errors:

C:\Documents and Settings\student\Desktop\acm_mp3.cpp(79) : error C2143: syntax error : missing ')' before 'string'
C:\Documents and Settings\student\Desktop\acm_mp3.cpp(79) : error C2143: syntax error : missing ';' before 'string'
C:\Documents and Settings\student\Desktop\acm_mp3.cpp(79) : fatal error C1004: unexpected end of file found

If I comment the #define SOURCE_MP3 "song.mp3" line the program compiles but a dialog appears and reads "argument required (mp3 file)!"

Any suggestions would be greatly appreciated!

[Disch]

Macros are evil.

There's a semicolon at the end of your #define SOURCE_MP3 line. Get rid of it.


Or better yet change your #define to a constant:

static const char* SOURCE_MP3 = "song.mp3";

[tripper]

Thanks for the suggestion Disch! I changed my #define to a constant and that eliminated several errors, but there is one more which reads:

64: 'CreateFileW' : cannot convert parameter 1 from 'const char [6]' to 'LPCWSTR'
1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

When I double click the error it points to the following line:

hComm = CreateFile("COM1:", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

What is happening? I've read my c++ textbook, but I don't know how to eliminate this error?

Any suggestions?

[chrisname]

Well; that depends. Which of those is a 6 element character array constant?

[Disch]

Unicode error. I'm in the midst of writing an Aritcle on this very topic.

You need to do one of the following. Note these are listed in order of recommendtation. (#1 is the preferred solution)

1) Use Win32 Unicode friendly strings (wide or tchar):

CreateFile( _T("COM1:")  //...  <--- note the _T() 

2) Explicitly call the non-Unicode version of CreateFile:

CreateFileA( "COM1:" // <---- note the A in CreateFileA 

3) Don't build in Unicode. Either #undef UNICODE before you include windows.h, or change your project settings to not build in unicode. The latter solution is preferable.


EDIT:

Actually, since you're using char* all over the place, you pretty much are destroying Unicode possibilities. The easiest route would be #3... but then you won't have a Unicode friendly program (won't be able to open filenames with foreign characters in the name).

A better solution would be to be Unicode friendly, but it might take a bit of work. I should have my article finished by today if you're interested in learning.

[tripper]

I just read the wiki page on Unicode since I was not that familiar with the terminology. It's a very interesting concept and it makes a lot of sense. Please point me to your article so I can become more familiar with Unicode.

I'm a little short on time to complete this code; I would like to finish it by tomorrow. But after my deadline, it would be interesting to make this code UNICODE friendly when I have more freedom.

I just want to make sure that I understand what you have suggested. I can either 1)include #undef UNICODE before including windows.h 2) use CreateFileA( "COM1:" 3) change project settings or 4) make it UNICODE friendly.

Another question, how does using char* make this code non-UNICODE friendly?

[helios]

change your project settings to not build in unicode. The latter solution is preferable.

All that really does is tell the compiler to not define UNICODE.

1)include #undef UNICODE before including windows.h

No.

#ifdef UNICODE
#undef UNICODE
#endif
#include <windows.h> 

Another question, how does using char* make this code non-UNICODE friendly?

Because the wide character versions take pointers to wchar_t.

[Disch]

Please point me to your article so I can become more familiar with Unicode.

It's not perfect, but here you go:

http://cplusplus.com/forum/articles/16820/

[tripper]

Thanks, its an interesting read.

I was able to compile the program with the offered suggestions. Unfortunately the other problem that I encountered pertained to the line 11 when I removed the forward slashes. I received a compile error. I tired changing the line to static const char* output.pcm "c:\\dump.pcm" but this produces the error C2143.

Anny suggestions?

[Disch]

You can't have a . in an identifier name

static const char output_pcm = "c:\\dump.pcm";
//  "output_pcm" is fine
//  "output.pcm" is bad 

[tripper]

Thanks, I fixed this error. I deleted the forward slashes from lines 11 and 168 and still receive the following errors which point to lines 10&11:

C:\Documents and Settings\student\Desktop\acm_mp3.cpp(10) : error C2059: syntax error : 'string'
C:\Documents and Settings\student\Desktop\acm_mp3.cpp(10) : error C2143: syntax error : missing ';' before 'string'
C:\Documents and Settings\student\Desktop\acm_mp3.cpp(11) : error C2143: syntax error : missing ';' before 'string'
C:\Documents and Settings\student\Desktop\acm_mp3.cpp(11) : fatal error C1004: unexpected end of file found

I'm at my wits end! What else am I missing?

[helios]

A * between 'const char' and the identifier?