dequant.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
 *
 * dequant.c - wrapper for IPP primitive which reconstructs the dequantized spectrum
 *               from scale factors and decoded Huffman codewords
 **************************************************************************************/

#include "coder.h"	

/**************************************************************************************
 * Function:    Dequantize
 *
 * Description: dequantize coefficients, decode stereo, reorder short blocks
 *                (one granule-worth)
 *
 * Inputs:      MP3DecInfo structure filled by UnpackFrameHeader(), UnpackSideInfo(),
 *                UnpackScaleFactors(), and DecodeHuffman() (for this granule)
 *              index of current granule
 *
 * Outputs:     dequantized and reordered coefficients in hi->huffDecBuf[0] 
 *                (one granule-worth, all channels)
 *              operates in-place on huffDecBuf but also needs di->workBuf
 *              updated hi->nonZeroBound index for both channels
 *
 * Return:      0 on success,  -1 if null input pointers
 **************************************************************************************/
int Dequantize(MP3DecInfo *mp3DecInfo, int gr)
{
	FrameHeader *fh;
	IppMP3FrameHeader *fhIPP;
	SideInfo *si;
	IppMP3SideInfo *siIPP;
	ScaleFactorInfo *sfi;
	HuffmanInfo *hi;
	DequantInfo *di;

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

	fh = (FrameHeader *)(mp3DecInfo->FrameHeaderPS);
	fhIPP = &(fh->fhIPP);

	/* 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);		/* does both channels at a time, so just offset to ch[0] of correct granule */

	sfi = (ScaleFactorInfo *)mp3DecInfo->ScaleFactorInfoPS;
	hi = (HuffmanInfo *)mp3DecInfo->HuffmanInfoPS;
	di = (DequantInfo *)mp3DecInfo->DequantInfoPS;

	/* IPP primitive #5 - dequantize, stereo decode, short block reorder */
	ippsReQuantize_MP3_32s_I(hi->huffDecBuf[0], hi->nonZeroBound, sfi->scaleFactor[0], siIPP, fhIPP, di->workBuf);

	return 0;
}