| /* ------------------------------------------------------------------ |
| * Copyright (C) 1998-2009 PacketVideo |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either |
| * express or implied. |
| * See the License for the specific language governing permissions |
| * and limitations under the License. |
| * ------------------------------------------------------------------- |
| */ |
| /* |
| ------------------------------------------------------------------------------ |
| |
| PacketVideo Corp. |
| MP3 Decoder Library |
| |
| Filename: pvmp3_huffman_decoding.cpp |
| |
| Funtions: |
| pvmp3_huffman_quad_decoding |
| pvmp3_huffman_pair_decoding |
| pvmp3_huffman_pair_decoding_linbits |
| |
| Date: 09/21/2007 |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| |
| Description: |
| |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| Inputs: |
| struct huffcodetab *h, pointer to huffman code record |
| int32 *x, returns decoded x value |
| int32 *y, returns decoded y value |
| int32 *v, returns decoded v value (only in quad function) |
| int32 *w, returns decoded w value (only in quad function) |
| tbits *pMainData bit stream |
| |
| Outputs: |
| |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| These functions are used to decode huffman codewords from the input |
| bitstream using combined binary search and look-up table approach. |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| [1] ISO MPEG Audio Subgroup Software Simulation Group (1996) |
| ISO 13818-3 MPEG-2 Audio Decoder - Lower Sampling Frequency Extension |
| |
| |
| ------------------------------------------------------------------------------ |
| PSEUDO-CODE |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| |
| /*---------------------------------------------------------------------------- |
| ; INCLUDES |
| ----------------------------------------------------------------------------*/ |
| #include "pvmp3_dec_defs.h" |
| #include "pv_mp3_huffman.h" |
| #include "pvmp3_getbits.h" |
| |
| |
| /*---------------------------------------------------------------------------- |
| ; MACROS |
| ; Define module specific macros here |
| ----------------------------------------------------------------------------*/ |
| |
| |
| /*---------------------------------------------------------------------------- |
| ; DEFINES |
| ; Include all pre-processor statements here. Include conditional |
| ; compile variables also. |
| ----------------------------------------------------------------------------*/ |
| |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL FUNCTION DEFINITIONS |
| ; Function Prototype declaration |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL STORE/BUFFER/POINTER DEFINITIONS |
| ; Variable declaration - defined here and used outside this module |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; EXTERNAL FUNCTION REFERENCES |
| ; Declare functions defined elsewhere and referenced in this module |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES |
| ; Declare variables used in this module but defined elsewhere |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; FUNCTION CODE |
| ----------------------------------------------------------------------------*/ |
| |
| |
| void pvmp3_huffman_quad_decoding(struct huffcodetab *h, |
| int32 *is, |
| tmp3Bits *pMainData) |
| { |
| |
| int32 x; |
| int32 y; |
| int32 v; |
| int32 w; |
| |
| y = (*h->pdec_huff_tab)(pMainData); |
| |
| |
| if (y) |
| { |
| v = (y >> 3); |
| |
| if (v) |
| { |
| if (get1bit(pMainData)) |
| { |
| v = -v; |
| } |
| } |
| w = (y >> 2) & 1; |
| if (w) |
| { |
| if (get1bit(pMainData)) |
| { |
| w = -w; |
| } |
| } |
| x = (y >> 1) & 1; |
| if (x) |
| { |
| if (get1bit(pMainData)) |
| { |
| x = -x; |
| } |
| } |
| y = y & 1; |
| if (y) |
| { |
| if (get1bit(pMainData)) |
| { |
| y = -y; |
| } |
| } |
| |
| } |
| else |
| { |
| v = 0; |
| w = 0; |
| x = 0; |
| |
| } |
| |
| *is = v; |
| *(is + 1) = w; |
| *(is + 2) = x; |
| *(is + 3) = y; |
| |
| } |
| |
| |
| |
| void pvmp3_huffman_pair_decoding(struct huffcodetab *h, /* pointer to huffman code record */ |
| int32 *is, |
| tmp3Bits *pMainData) |
| { |
| /* Lookup in Huffman table. */ |
| int32 x; |
| int32 y; |
| |
| uint16 cw = (*h->pdec_huff_tab)(pMainData); |
| |
| /* Process sign and escape encodings for dual tables. */ |
| |
| |
| if (cw) |
| { |
| x = cw >> 4; |
| |
| if (x) |
| { |
| if (get1bit(pMainData)) |
| { |
| x = -x; |
| } |
| y = cw & 0xf; |
| if (y && get1bit(pMainData)) |
| { |
| y = -y; |
| } |
| |
| } |
| else |
| { |
| y = cw & 0xf; |
| if (get1bit(pMainData)) |
| { |
| y = -y; |
| } |
| } |
| |
| *is = x; |
| *(is + 1) = y; |
| } |
| else |
| { |
| *is = 0; |
| *(is + 1) = 0; |
| } |
| |
| |
| |
| } |
| |
| |
| |
| |
| void pvmp3_huffman_pair_decoding_linbits(struct huffcodetab *h, /* pointer to huffman code record */ |
| int32 *is, |
| tmp3Bits *pMainData) |
| { |
| int32 x; |
| int32 y; |
| |
| uint16 cw; |
| /* Lookup in Huffman table. */ |
| |
| |
| cw = (*h->pdec_huff_tab)(pMainData); |
| x = cw >> 4; |
| |
| /* Process sign and escape encodings for dual tables. */ |
| |
| |
| if (15 == (uint32)x) |
| { |
| int32 tmp = getUpTo17bits(pMainData, (h->linbits + 1)); |
| x += tmp >> 1; |
| if (tmp&1) |
| { |
| x = -x; |
| } |
| } |
| else if (x) |
| { |
| if (get1bit(pMainData)) |
| { |
| x = -x; |
| } |
| } |
| |
| y = cw & 0xf; |
| if (15 == (uint32)y) |
| { |
| int32 tmp = getUpTo17bits(pMainData, (h->linbits + 1)); |
| y += tmp >> 1; |
| if (tmp&1) |
| { |
| y = -y; |
| } |
| } |
| else if (y) |
| { |
| if (get1bit(pMainData)) |
| { |
| y = -y; |
| } |
| } |
| |
| *is = x; |
| *(is + 1) = y; |
| |
| } |
| |
| |
| |
| |
| |