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Understanding Audio Input and Output with Multimedia API: A Comprehensive Overview

This document explores the functionalities of audio input and output using the Multimedia API, specifically focusing on Wave file format handling. It details essential structures like WAVEFORMATEX and WAVEHDR, which define the audio data format and buffer headers, respectively. The document encompasses function calls such as waveInOpen(), waveInStart(), and waveOutOpen() for recording and playback operations. A sample program demonstrates the practical implementation of these functions, guiding users to record and play back audio effectively while managing file operations with RIFF chunks.

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Understanding Audio Input and Output with Multimedia API: A Comprehensive Overview

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  1. Audio input and output Speaker: Ching Chen Chang Date:2006.10.30

  2. Outline • Multi-Media API (Input) • Wave File Format • Multi-Media API (Output) • Sample program • record1.cpp

  3. WAVEFORMATEX • typedef struct { WORD wFormatTag; WORD nChannels; DWORD nSamplesPerSec; DWORD nAvgBytesPerSec; WORD nBlockAlign; WORD wBitsPerSample; WORD cbSize; } WAVEFORMATEX; • This structure defines the format of waveform-audio data.

  4. WAVEHDR • typedef struct { LPSTR lpData; DWORD dwBufferLength; DWORD dwBytesRecorded; DWORD dwUser; DWORD dwFlags; DWORD dwLoops; struct wavehdr_tag* lpNext; DWORD reserved; }WAVEHDR; • This structure defines the header used to identify a waveform-audio buffer.

  5. waveInOpen() • MMRESULT waveInOpen(HWAVEIN &ihandle,UINTDeviceID,WAVEFORMATEX &waveformat,DWORDdwCallback,DWORDdwInstance,DWORDfdwOpen ); • Open a specified waveform input device for recording. • uDeviceID : WAVE_MAPPER • fdwOpen :CALLBACK_WINDOW ,CALLBACK_THREAD • Return MMSYSERR_NOERROR means success

  6. waveInPrepareHeader() • MMRESULT waveInPrepareHeader(HWAVEINihandle,WAVEHDR &wh,UINTcbwh ); • Prepares a buffer for waveform input. • Returns MMSYSERR_NOERROR if successful.

  7. waveInAddBuffer() • MMRESULT waveInAddBuffer(HWAVEIN ihandle,WAVEHDR &wh,UINTcbwh ); • Sends an input buffer to the specified waveform-audio input device. • Returns MMSYSERR_NOERROR if successful.

  8. waveInStart() • MMRESULT waveInStart(HWAVEIN ihandle ); • Starts input on the specified waveform input device. • Returns MMSYSERR_NOERROR if successful.

  9. waveInReset() • MMRESULT waveInReset(HWAVEINihandle ); • Stops input on a specified waveform input device and resets the current position to 0. • Returns MMSYSERR_NOERROR if successful.

  10. waveInUnprepareHeader() • MMRESULT waveInUnprepareHeader(HWAVEIN ihandle,WAVEHDR&wh,UINTcbwh ); • Cleans up the preparation performed by waveInPrepareHeader. • Returns MMSYSERR_NOERROR if successful.

  11. waveInClose() • MMRESULT waveInClose(HWAVEIN ihandle); • Closes the specified waveform-audio input device. • Returns MMSYSERR_NOERROR if successful.

  12. Wave File Format

  13. MMCKINFO • typedef struct { FOURCC ckid; DWORD cksize; FOURCC fccType; DWORD dwDataOffset; DWORD dwFlags; } MMCKINFO; • The structure contains information about a chunk in a RIFF file.

  14. mmioOpen() • HMMIO mmioOpen( LPSTR Filename, MMIOINFO mmioinfo, DWORD dwOpenFlags ); • The mmioOpen function opens a file for unbuffered or buffered I/O. • Returns a handle of the opened file. • If the file cannot be opened, the return value is NULL. • dwOpenFlags:MMIO_CREATE、MMIO_WRITE、MMIO_READ …etc.

  15. mmioCreateChunk() • MMRESULT mmioCreateChunk( HMMIO hmmio, MMCKINFO &ck, UINT wFlags ); • The mmioCreateChunk function creates a chunk in a RIFF file that was opened by using the mmioOpenfunction. • wFlags :MMIO_CREATERIFF • Returns MMSYSERR_NOERROR if successful

  16. mmioFOURCC() • FOURCC mmioFOURCC( CHAR ch0, CHAR ch1, CHAR ch2, CHAR ch3 ); • The mmioFOURCC macro converts four characters into a four-character code. • Returns the four-character code created from the given characters.

  17. mmioWrite() • LONG mmioWrite( HMMIO hmmio, char _huge* pch, LONG cch ); • The mmioWrite function writes a specified number of bytes to a file opened by using the mmioOpenfunction • Returns the number of bytes actually written.

  18. mmioAscend() • MMRESULT mmioAscend( HMMIO hmmio, MMCKINFO &ck, UINT wFlags ); • The mmioAscend function ascends out of a chunk in a RIFF file • wFlags : must be zero. • Returns MMSYSERR_NOERROR if successful

  19. mmioClose() • MMRESULT mmioClose( HMMIO hmmio, UINT wFlags ); • Returns zero if successful or an error otherwise.

  20. waveOutOpen() • MMRESULT waveOutOpen(HWAVEOUT &ohandle,UINTuDeviceID,WAVEFORMATEX &wf,DWORDdwCallback,DWORDdwInstance,DWORDfdwOpen ); • Opens a specified waveform output device for playback. • Returns MMSYSERR_NOERROR if successful.

  21. waveOutPrepareHeader() • MMRESULT waveOutPrepareHeader(HWAVEOUTohandle,WAVEHDR &wh,UINTcbwh ); • Prepares a waveform data block for playback. • Returns MMSYSERR_NOERROR if successful.

  22. waveOutWrite() • MMRESULT waveOutWrite(HWAVEOUT ohandle,WAVEHDR&wh,UINTcbwh ); • Sends a data block to the specified waveform output device. • Returns MMSYSERR_NOERROR if successful.

  23. waveOutReset() • MMRESULT waveOutReset(HWAVEOUTohandle ); • Stops playback on a specified waveform output device and resets the current position to 0. • Returns MMSYSERR_NOERROR if successful.

  24. waveOutUnprepareHeader() • MMRESULT waveOutUnprepareHeader(HWAVEOUTohandle,WAVEHDR&wh,UINTcbwh ); • Cleans up the preparation performed by waveOutPrepareHeader. • Returns MMSYSERR_NOERROR if successful.

  25. waveOutClose( ) • MMRESULT waveOutClose(HWAVEOUTohandle ); • Closes the specified waveform output device. • Returns MMSYSERR_NOERROR if successful.

  26. Sample Program • Record • Produce the Wave file • Play the record voice • nChannels=1 • nSamplesPerSec=8000 • wBitsPerSample=8 • Demo • http://ms11.voip.edu.tw/~beautidays/recordcode.txt

  27. Reference(1/2) • Wavefomat http://ccrma.stanford.edu/CCRMA/Courses/422 /projects/WaveFormat/ http://www.sonicspot.com/guide/wavefiles.html • Multimedia FILE I/O http://msdn.microsoft.com/library/default.asp?url=/library/en-us/multimed/htm/_win32_multimedia_file_i_o.asp

  28. Reference(2/2) • Waveform Audio http://msdn.microsoft.com/library/default.asp?url=/library/en-us/multimed/htm/_win32_about_waveform_audio.asp

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