imdct.c

著名的 helix realplayer 基于手机 symbian 系统的 播放器全套源代码

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/**************************************************************************************
 * Fixed-point MP3 decoder using Intel IPP libraries
 * June 2003
 *
 * imdct.c - wrapper for IPP primitive which calculates inverse MDCT
 **************************************************************************************/

#include "coder.h"	

/**************************************************************************************
 * Function:    IMDCT
 *
 * Description: do alias reduction, inverse MDCT, overlap-add, and frequency inversion
 *
 * Inputs:      MP3DecInfo structure filled by UnpackFrameHeader(), UnpackSideInfo(),
 *                UnpackScaleFactors(), and DecodeHuffman() (for this granule, channel)
 *                includes PCM samples in overBuf (from last call to IMDCT) for OLA
 *              index of current granule and channel
 *
 * Outputs:     PCM samples in outBuf, for input to subband transform
 *              PCM samples in overBuf, for OLA next time
 *              updated hi->nonZeroBound index for this channel
 *
 * Return:      0 on success,  -1 if null input pointers
 **************************************************************************************/
int IMDCT(MP3DecInfo *mp3DecInfo, int gr, int ch)
{
	SideInfo *si;
	IppMP3SideInfo *siIPP;
	HuffmanInfo *hi;
	IMDCTInfo *mi;

	/* validate pointers */
	if (!mp3DecInfo || !mp3DecInfo->SideInfoPS || !mp3DecInfo->HuffmanInfoPS || !mp3DecInfo->IMDCTInfoPS)
		return -1;

	/* si is an array of up to 4 structs, stored as gr0ch0, gr0ch1, gr1ch0, gr1ch1 */
	si = (SideInfo *)(mp3DecInfo->SideInfoPS);
	siIPP = &(si->siIPP[0]);
	siIPP += (gr*mp3DecInfo->nChans + ch);

	hi = (HuffmanInfo*)(mp3DecInfo->HuffmanInfoPS);
	mi = (IMDCTInfo *)(mp3DecInfo->IMDCTInfoPS);
	
	/* IPP primitive #6 - alias reduction, inverse MDCT, overlap-add, frequency inversion */
	ippsMDCTInv_MP3_32s(hi->huffDecBuf[ch], mi->outBuf[ch], mi->overBuf[ch], hi->nonZeroBound[ch], 
		&(mi->numPrevIMDCT[ch]), siIPP->blockType, siIPP->mixedBlock);

	return 0;
}