ISD9160学习笔记03_ISD9160音频解码代码分析

BOOL App_StartPlay(void)
{
	// Initiate NuLiteEx audio decode lib with callback functions stored in g_asAppCallBack[0]
	NuLiteExApp_DecodeInitiate(&g_sApp.sNuLiteExAppDecode, (UINT8 *)&g_sApp.uTempBuf, 0);
	
	// Start NuLiteEx decode lib to decode NuLiteEx file stored from address and played from audio channel 0.
	// And decode the first frame of PCMs.
	if ( NuLiteExApp_DecodeStartPlayByAddr(&g_sApp.sNuLiteExAppDecode, AUDIOROM_STORAGE_START_ADDR, 0) == FALSE )
		return FALSE;

	// Light playback led(PB9) for display status.
	OUT4(0);
	
	// Start Ultraio Timer & HW pwm for UltraIO curve output
	ULTRAIO_START();
	
	// Start to playback audio. 
	Playback_StartPlay();
}

BOOL NuLiteExApp_DecodeStartPlayByAddr(S_NULITEEX_APP_DECODE *psNuLiteExAppDecode, UINT32 u32NuLiteExStorageStartAddr, UINT8 u8PlaybackChannel)
{
	UINT16 u16SampleRate;
	// NuLiteEx解码库初始化对应的工作缓冲区，应用层传入temp缓存来方便解码库内部工作。另外根据传入的SPI地址从SPI取文件，获取采样率。
	// NuLiteEx decoder initiates work buffer and returns sample rate.
	if ( (u16SampleRate = NuLiteEx_DecodeInitiate(	(UINT8*)psNuLiteExAppDecode->au32DecodeWorkBuf, 
													psNuLiteExAppDecode->pau8TempBuf, 
													u32NuLiteExStorageStartAddr, 
													g_asAppCallBack[psNuLiteExAppDecode->u8CallbackIndex].pfnReadDataCallback )) == 0 )
		return FALSE;	

	// 给Playback模块对接对应的工作缓冲区，方便其下一步播放。
	// Initiate and set output buffer variable(include frame size, buffer size etc.) 
	Playback_SetOutputBuf( 	&psNuLiteExAppDecode->sOutBufCtrl,
							NULITEEXAPP_OUT_BUF_SIZE,
							psNuLiteExAppDecode->i16OutBuf,
							NULITEEXAPP_OUT_SAMPLES_PER_FRAME,
							u16SampleRate );
	
	// 工作缓冲区，置有效位。
	// Trigger active flag of output buffer for NuLiteEx decoding
	BUF_CTRL_SET_ACTIVE(&psNuLiteExAppDecode->sOutBufCtrl);

	// 工作缓冲区中的读写指针赋值。
	// Pre-decode one frame
	psNuLiteExAppDecode->sOutBufCtrl.u16BufWriteIdx = NULITEEXAPP_OUT_SAMPLES_PER_FRAME;
	if ( NuLiteExApp_DecodeProcess(psNuLiteExAppDecode) == FALSE )
	{
		BUF_CTRL_SET_INACTIVE(&psNuLiteExAppDecode->sOutBufCtrl);
		return FALSE;
	}
	psNuLiteExAppDecode->sOutBufCtrl.u16BufReadIdx = NULITEEXAPP_OUT_SAMPLES_PER_FRAME;
	
	// 记录当前播放的channel，用来停止播放。
	// Record play channel index for stopping to play.
	psNuLiteExAppDecode->u8PlaybackChannel = u8PlaybackChannel;
	// 准备播放，把这里的循环缓冲区同playback共用。
	// Add audio codec into channel and preper to play codec.
	Playback_Add(psNuLiteExAppDecode->u8PlaybackChannel, &psNuLiteExAppDecode->sOutBufCtrl);

	return TRUE;
}

void Playback_StartPlay(void)
{
	INT16 *pi16PcmBuf;
	
	if( s_u8PlayCtrl == PLAYBACK_NOACTION ) // 这个s_u8PlayCtrl是playback模块内部处理的。
	{
		#if ( PLAYBACK_CHANNEL_COUNT > 1)
		pi16PcmBuf = g_ai16DACSamples;
		#else
		pi16PcmBuf = &g_psDacBufCtrl->pi16Buf[g_psDacBufCtrl->u16BufReadIdx];// PCM数据缓冲区复制。
		#endif
		
		#if ((APU_FILTER_ENABLE == 1)&&(APU_UPSAMPLE == 2))
		NuDACFilterEx_Up2Initial(g_au8Up2WorkBuf);
		#elif ((APU_FILTER_ENABLE == 1)&&(APU_UPSAMPLE == 4))
		NuDACFilterEx_Up4Initial(g_au8Up4WorkBuf);
		#endif
		g_u8AppCtrl|=APPCTRL_PLAY;
		s_u8PlayCtrl |= PLAYBACK_START;
		#if (APU_ENABLE)
		{
			UINT8 u8Count;
			
			for( u8Count = 0; u8Count < 8; u8Count ++)
				g_ai16DACSamples[u8Count] = 0;		//Clear virtual buffer
		}
		#endif
		
		Playback_ResetChannelVolume(0);
		
		SPK_Start(); // 这里头开始调用DPWM来播放DPWM->DATA，DPWM_START_PLAY(DPWM);
		
		#if (APU_PDMA_ENABLE)
		PdmaCtrl_Start(APU_PDMA_CH, (uint32_t *)pi16PcmBuf, (uint32_t *)&DPWM->DATA, 8);// 将PCM缓冲数据传到DPWM->DATA中。
		#endif
		
	}
}

// Continue decode NuLiteEx data to produce PCMs for audio playback.
if ( NuLiteExApp_DecodeProcess(&g_sApp.sNuLiteExAppDecode) == TRUE )

BOOL NuLiteExApp_DecodeProcess(S_NULITEEX_APP_DECODE *psNuLiteExAppDecode)
{
	INT16 *pi16OutBuf;
	
	// 环形缓冲区非激活状态，这个只有在应用层置位(按键停止、或者启动失败等情况)
	if (BUF_CTRL_IS_INACTIVE(&psNuLiteExAppDecode->sOutBufCtrl))
		return FALSE;
	
	// 环形缓冲区还有未读数据
	if ( Playback_NeedUpdateOutputBuf(&psNuLiteExAppDecode->sOutBufCtrl) )
	{
		// 由核心库来判断这个文件是否解析完了
		// Check end of file
		if(NuLiteEx_DecodeIsEnd((UINT8*)psNuLiteExAppDecode->au32DecodeWorkBuf))
		{
			// Trigger inactive flag of output buffer to stop NuLiteEx decoding
			BUF_CTRL_SET_INACTIVE(&psNuLiteExAppDecode->sOutBufCtrl);
			// Use to represnt no active(or end) of decoding
			psNuLiteExAppDecode->sOutBufCtrl.u16SampleRate = 0;
			return FALSE;
		}

		// Record output data buffer pointer(for duplicate & process)
		pi16OutBuf = (PINT16)&psNuLiteExAppDecode->sOutBufCtrl.pi16Buf[psNuLiteExAppDecode->sOutBufCtrl.u16BufWriteIdx];
		
		// 核心库继续发挥其巨大作用，开足马力读取文件中PCM数据转到缓冲区。
		NuLiteEx_DecodeProcess(	(UINT8*)psNuLiteExAppDecode->au32DecodeWorkBuf, 
								psNuLiteExAppDecode->pau8TempBuf, 
								pi16OutBuf, 
								g_asAppCallBack[psNuLiteExAppDecode->u8CallbackIndex].pfnReadDataCallback, 
								g_asAppCallBack[psNuLiteExAppDecode->u8CallbackIndex].pfnUserEventCallback);

		// PlayBack依旧共享这个缓冲区，准备对数据进行进一步处理
		// Update write index of output buffer and avoid buffer overflow
		Playback_UpdateOutputBuf(&psNuLiteExAppDecode->sOutBufCtrl);

		// Duplicate data into buffer for using duplication callback function.
		if ( psNuLiteExAppDecode->u8CtrlFlag&(NULITEEXAPP_CTRL_DUPLICATE_TO_BUF|NULITEEXAPP_CTRL_DUPLICATE_TO_FUNC) )
		{
			if ( psNuLiteExAppDecode->u8CtrlFlag & NULITEEXAPP_CTRL_DUPLICATE_TO_BUF )
				BufCtrl_WriteWithCount(psNuLiteExAppDecode->psDuplicateOutBufCtrl, NULITEEXAPP_OUT_SAMPLES_PER_FRAME, pi16OutBuf );
			else 
				psNuLiteExAppDecode->pfnDuplicateFunc(NULITEEXAPP_OUT_SAMPLES_PER_FRAME, pi16OutBuf);
		}		
	}	
	return TRUE;
}