sdl_dx5audio.c

MPEG-4编解码的实现(包括MPEG4视音频编解码)

		SetDSerror("DirectSound GetCurrentPosition", result);
		return(NULL);
	}
	cursor /= mixlen;
	playing = cursor;
	cursor = (cursor+1)%NUM_BUFFERS;
	cursor *= mixlen;

	/* Lock the audio buffer */
	result = IDirectSoundBuffer_Lock(mixbuf, cursor, mixlen,
				(LPVOID *)&locked_buf, &rawlen, NULL, &junk, 0);
	if ( result == DSERR_BUFFERLOST ) {
		IDirectSoundBuffer_Restore(mixbuf);
		result = IDirectSoundBuffer_Lock(mixbuf, cursor, mixlen,
				(LPVOID *)&locked_buf, &rawlen, NULL, &junk, 0);
	}
	if ( result != DS_OK ) {
		SetDSerror("DirectSound Lock", result);
		return(NULL);
	}
	return(locked_buf);
}

static void DX5_WaitDone(_THIS)
{
	Uint8 *stream;

	/* Wait for the playing chunk to finish */
	stream = this->GetAudioBuf(this);
	if ( stream != NULL ) {
		memset(stream, silence, mixlen);
		this->PlayAudio(this);
	}
	this->WaitAudio(this);

	/* Stop the looping sound buffer */
	IDirectSoundBuffer_Stop(mixbuf);
}

static void DX5_CloseAudio(_THIS)
{
	if ( sound != NULL ) {
		if ( mixbuf != NULL ) {
			/* Clean up the audio buffer */
			IDirectSoundBuffer_Release(mixbuf);
			mixbuf = NULL;
		}
		if ( audio_event != NULL ) {
			CloseHandle(audio_event);
			audio_event = NULL;
		}
		IDirectSound_Release(sound);
		sound = NULL;
	}
}

/* This function tries to create a primary audio buffer, and returns the
   number of audio chunks available in the created buffer.
*/
static int CreatePrimary(LPDIRECTSOUND sndObj, HWND focus, 
	LPDIRECTSOUNDBUFFER *sndbuf, WAVEFORMATEX *wavefmt, Uint32 chunksize)
{
	HRESULT result;
	DSBUFFERDESC format;
	DSBCAPS caps;
	int numchunks;

	/* Try to set primary mixing privileges */
	result = IDirectSound_SetCooperativeLevel(sndObj, focus,
							DSSCL_WRITEPRIMARY);
	if ( result != DS_OK ) {
#ifdef DEBUG_SOUND
		SetDSerror("DirectSound SetCooperativeLevel", result);
#endif
		return(-1);
	}

	/* Try to create the primary buffer */
	memset(&format, 0, sizeof(format));
	format.dwSize = sizeof(format);
	format.dwFlags=(DSBCAPS_PRIMARYBUFFER|DSBCAPS_GETCURRENTPOSITION2);
	format.dwFlags |= DSBCAPS_STICKYFOCUS;
#ifdef USE_POSITION_NOTIFY
	format.dwFlags |= DSBCAPS_CTRLPOSITIONNOTIFY;
#endif
	result = IDirectSound_CreateSoundBuffer(sndObj, &format, sndbuf, NULL);
	if ( result != DS_OK ) {
#ifdef DEBUG_SOUND
		SetDSerror("DirectSound CreateSoundBuffer", result);
#endif
		return(-1);
	}

	/* Check the size of the fragment buffer */
	memset(&caps, 0, sizeof(caps));
	caps.dwSize = sizeof(caps);
	result = IDirectSoundBuffer_GetCaps(*sndbuf, &caps);
	if ( result != DS_OK ) {
#ifdef DEBUG_SOUND
		SetDSerror("DirectSound GetCaps", result);
#endif
		IDirectSoundBuffer_Release(*sndbuf);
		return(-1);
	}
	if ( (chunksize > caps.dwBufferBytes) ||
				((caps.dwBufferBytes%chunksize) != 0) ) {
		/* The primary buffer size is not a multiple of 'chunksize'
		   -- this hopefully doesn't happen when 'chunksize' is a 
		      power of 2.
		*/
		IDirectSoundBuffer_Release(*sndbuf);
		SDL_SetError(
"Primary buffer size is: %d, cannot break it into chunks of %d bytes\n",
					caps.dwBufferBytes, chunksize);
		return(-1);
	}
	numchunks = (caps.dwBufferBytes/chunksize);

	/* Set the primary audio format */
	result = IDirectSoundBuffer_SetFormat(*sndbuf, wavefmt);
	if ( result != DS_OK ) {
#ifdef DEBUG_SOUND
		SetDSerror("DirectSound SetFormat", result);
#endif
		IDirectSoundBuffer_Release(*sndbuf);
		return(-1);
	}
	return(numchunks);
}

/* This function tries to create a secondary audio buffer, and returns the
   number of audio chunks available in the created buffer.
*/
static int CreateSecondary(LPDIRECTSOUND sndObj, HWND focus,
	LPDIRECTSOUNDBUFFER *sndbuf, WAVEFORMATEX *wavefmt, Uint32 chunksize)
{
	const int numchunks = 2;
	HRESULT result;
	DSBUFFERDESC format;
	LPVOID pvAudioPtr1, pvAudioPtr2;
	DWORD  dwAudioBytes1, dwAudioBytes2;

	/* Try to set primary mixing privileges */
	if ( focus ) {
		result = IDirectSound_SetCooperativeLevel(sndObj,
					focus, DSSCL_PRIORITY);
	} else {
		result = IDirectSound_SetCooperativeLevel(sndObj,
					GetDesktopWindow(), DSSCL_NORMAL);
	}
	if ( result != DS_OK ) {
#ifdef DEBUG_SOUND
		SetDSerror("DirectSound SetCooperativeLevel", result);
#endif
		return(-1);
	}

	/* Try to create the secondary buffer */
	memset(&format, 0, sizeof(format));
	format.dwSize = sizeof(format);
	format.dwFlags = DSBCAPS_GETCURRENTPOSITION2;
#ifdef USE_POSITION_NOTIFY
	format.dwFlags |= DSBCAPS_CTRLPOSITIONNOTIFY;
#endif
	if ( ! focus ) {
		format.dwFlags |= DSBCAPS_GLOBALFOCUS;
	} else {
		format.dwFlags |= DSBCAPS_STICKYFOCUS;
	}
	format.dwBufferBytes = numchunks*chunksize;
	if ( (format.dwBufferBytes < DSBSIZE_MIN) ||
	     (format.dwBufferBytes > DSBSIZE_MAX) ) {
		SDL_SetError("Sound buffer size must be between %d and %d",
				DSBSIZE_MIN/numchunks, DSBSIZE_MAX/numchunks);
		return(-1);
	}
	format.dwReserved = 0;
	format.lpwfxFormat = wavefmt;
	result = IDirectSound_CreateSoundBuffer(sndObj, &format, sndbuf, NULL);
	if ( result != DS_OK ) {
		SetDSerror("DirectSound CreateSoundBuffer", result);
		return(-1);
	}
	IDirectSoundBuffer_SetFormat(*sndbuf, wavefmt);

	/* Silence the initial audio buffer */
	result = IDirectSoundBuffer_Lock(*sndbuf, 0, format.dwBufferBytes,
	                                 (LPVOID *)&pvAudioPtr1, &dwAudioBytes1,
	                                 (LPVOID *)&pvAudioPtr2, &dwAudioBytes2,
	                                 DSBLOCK_ENTIREBUFFER);
	if ( result == DS_OK ) {
		if ( wavefmt->wBitsPerSample == 8 ) {
			memset(pvAudioPtr1, 0x80, dwAudioBytes1);
		} else {
			memset(pvAudioPtr1, 0x00, dwAudioBytes1);
		}
		IDirectSoundBuffer_Unlock(*sndbuf,
		                          (LPVOID)pvAudioPtr1, dwAudioBytes1,
		                          (LPVOID)pvAudioPtr2, dwAudioBytes2);
	}

	/* We're ready to go */
	return(numchunks);
}

/* This function tries to set position notify events on the mixing buffer */
#ifdef USE_POSITION_NOTIFY
static int CreateAudioEvent(_THIS)
{
	LPDIRECTSOUNDNOTIFY notify;
	DSBPOSITIONNOTIFY *notify_positions;
	int i, retval;
	HRESULT result;

	/* Default to fail on exit */
	retval = -1;
	notify = NULL;

	/* Query for the interface */
	result = IDirectSoundBuffer_QueryInterface(mixbuf,
			&IID_IDirectSoundNotify, (void *)&notify);
	if ( result != DS_OK ) {
		goto done;
	}

	/* Allocate the notify structures */
	notify_positions = (DSBPOSITIONNOTIFY *)malloc(NUM_BUFFERS*
					sizeof(*notify_positions));
	if ( notify_positions == NULL ) {
		goto done;
	}

	/* Create the notify event */
	audio_event = CreateEvent(NULL, FALSE, FALSE, NULL);
	if ( audio_event == NULL ) {
		goto done;
	}

	/* Set up the notify structures */
	for ( i=0; i<NUM_BUFFERS; ++i ) {
		notify_positions[i].dwOffset = i*mixlen;
		notify_positions[i].hEventNotify = audio_event;
	}
	result = IDirectSoundNotify_SetNotificationPositions(notify,
					NUM_BUFFERS, notify_positions);
	if ( result == DS_OK ) {
		retval = 0;
	}
done:
	if ( notify != NULL ) {
		IDirectSoundNotify_Release(notify);
	}
	return(retval);
}
#endif /* USE_POSITION_NOTIFY */

static int DX5_OpenAudio(_THIS, SDL_AudioSpec *spec)
{
	HRESULT      result;
	WAVEFORMATEX waveformat;

	/* Set basic WAVE format parameters */
	memset(&waveformat, 0, sizeof(waveformat));
	waveformat.wFormatTag = WAVE_FORMAT_PCM;

	/* Determine the audio parameters from the AudioSpec */
	switch ( spec->format & 0xFF ) {
		case 8:
			/* Unsigned 8 bit audio data */
			spec->format = AUDIO_U8;
			silence = 0x80;
			waveformat.wBitsPerSample = 8;
			break;
		case 16:
			/* Signed 16 bit audio data */
			spec->format = AUDIO_S16;
			silence = 0x00;
			waveformat.wBitsPerSample = 16;
			break;
		default:
			SDL_SetError("Unsupported audio format");
			return(-1);
	}
	waveformat.nChannels = spec->channels;
	waveformat.nSamplesPerSec = spec->freq;
	waveformat.nBlockAlign =
		waveformat.nChannels * (waveformat.wBitsPerSample/8);
	waveformat.nAvgBytesPerSec = 
		waveformat.nSamplesPerSec * waveformat.nBlockAlign;

	/* Update the fragment size as size in bytes */
	SDL_CalculateAudioSpec(spec);

	/* Open the audio device */
	result = DSoundCreate(NULL, &sound, NULL);
	if ( result != DS_OK ) {
		SetDSerror("DirectSoundCreate", result);
		return(-1);
	}

	/* Create the audio buffer to which we write */
	NUM_BUFFERS = -1;
	if ( mainwin ) {
		NUM_BUFFERS = CreatePrimary(sound, mainwin, &mixbuf,
						&waveformat, spec->size);
	}
	if ( NUM_BUFFERS < 0 ) {
		NUM_BUFFERS = CreateSecondary(sound, mainwin, &mixbuf,
						&waveformat, spec->size);
		if ( NUM_BUFFERS < 0 ) {
			return(-1);
		}
#ifdef DEBUG_SOUND
		fprintf(stderr, "Using secondary audio buffer\n");
#endif
	}
#ifdef DEBUG_SOUND
	else
		fprintf(stderr, "Using primary audio buffer\n");
#endif

	/* The buffer will auto-start playing in DX5_WaitAudio() */
	playing = 0;
	mixlen = spec->size;

#ifdef USE_POSITION_NOTIFY
	/* See if we can use DirectX 6 event notification */
	if ( CreateAudioEvent(this) == 0 ) {
		this->WaitAudio = DX6_WaitAudio_EventWait;
	} else {
		this->WaitAudio = DX5_WaitAudio_BusyWait;
	}
#endif
	return(0);
}

static int DX5_AudioDelayMsec (_THIS)
{
      DWORD cursor, write;
      HRESULT result;
      int odelay;
      /* char buffer[80]; */

      result = IDirectSoundBuffer_GetCurrentPosition(mixbuf, &cursor, &write);+       write = cursor / mixlen;
      write = (write+1)%NUM_BUFFERS;
      write *= mixlen;

      if (result == DS_OK) {
      /* 
       * delay in msec is bytes  * 1000 / (bytes per sample * channels * freq)+        */
              odelay = (write - cursor);
              odelay *= 1000;
              odelay /= this->spec.channels;
              if (!(this->spec.format == AUDIO_U8 ||  
                      this->spec.format == AUDIO_S8)) {
                      odelay /= 2; // 2 bytes per sample
              }
              odelay /= this->spec.freq;
              return odelay;
      } 
      return -1;
}