1  /* ***** BEGIN LICENSE BLOCK *****
 2   * Version: RCSL 1.0/RPSL 1.0
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 4   * Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved.
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34   * ***** END LICENSE BLOCK ***** */
35  
36  /**************************************************************************************
37   * Fixed-point MP3 decoder
38   * Jon Recker (jrecker@real.com), Ken Cooke (kenc@real.com)
39   * June 2003
40   *
41   * subband.c - subband transform (synthesis filterbank implemented via 32-point DCT
42   *               followed by polyphase filter)
43   **************************************************************************************/
44  
45  #include "coder.h"
46  #include "assembly.h"
47  
48  /**************************************************************************************
49   * Function:    Subband
50   *
51   * Description: do subband transform on all the blocks in one granule, all channels
52   *
53   * Inputs:      filled MP3DecInfo structure, after calling IMDCT for all channels
54   *              vbuf[ch] and vindex[ch] must be preserved between calls
55   *
56   * Outputs:     decoded PCM data, interleaved LRLRLR... if stereo
57   *
58   * Return:      0 on success,  -1 if null input pointers
59   **************************************************************************************/
60  int Subband(MP3DecInfo *mp3DecInfo, short *pcmBuf)
61  {
62  	int b;
63  	HuffmanInfo *hi;
64  	IMDCTInfo *mi;
65  	SubbandInfo *sbi;
66  
67  	/* validate pointers */
68  	if (!mp3DecInfo || !mp3DecInfo->HuffmanInfoPS || !mp3DecInfo->IMDCTInfoPS || !mp3DecInfo->SubbandInfoPS)
69  	return -1;
70  
71  	hi = (HuffmanInfo *)mp3DecInfo->HuffmanInfoPS;
72  	mi = (IMDCTInfo *)(mp3DecInfo->IMDCTInfoPS);
73  	sbi = (SubbandInfo*)(mp3DecInfo->SubbandInfoPS);
74  
75  	if (mp3DecInfo->nChans == 2) {
76  		/* stereo */
77  		for (b = 0; b < BLOCK_SIZE; b++) {
78  			FDCT32(mi->outBuf[0][b], sbi->vbuf + 0*32, sbi->vindex, (b & 0x01), mi->gb[0]);
79  			FDCT32(mi->outBuf[1][b], sbi->vbuf + 1*32, sbi->vindex, (b & 0x01), mi->gb[1]);
80  			PolyphaseStereo(pcmBuf, sbi->vbuf + sbi->vindex + VBUF_LENGTH * (b & 0x01), polyCoef);
81  			sbi->vindex = (sbi->vindex - (b & 0x01)) & 7;
82  			pcmBuf += (2 * NBANDS);
83  		}
84  		} else {
85  		/* mono */
86  		for (b = 0; b < BLOCK_SIZE; b++) {
87  			FDCT32(mi->outBuf[0][b], sbi->vbuf + 0*32, sbi->vindex, (b & 0x01), mi->gb[0]);
88  			PolyphaseMono(pcmBuf, sbi->vbuf + sbi->vindex + VBUF_LENGTH * (b & 0x01), polyCoef);
89  			sbi->vindex = (sbi->vindex - (b & 0x01)) & 7;
90  			pcmBuf += NBANDS;
91  		}
92  	}
93  
94  	return 0;
95  }
96