| /* |
| * Copyright (C) 2007-2008 ARM Limited |
| * |
| * 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. |
| * |
| */ |
| /** |
| * |
| * File Name: omxVCM4P2_DecodeVLCZigzag_IntraDCVLC.c |
| * OpenMAX DL: v1.0.2 |
| * Revision: 9641 |
| * Date: Thursday, February 7, 2008 |
| * |
| * |
| * |
| * |
| * Description: |
| * Contains modules for zigzag scanning and VLC decoding |
| * for intra block. |
| * |
| */ |
| |
| #include "omxtypes.h" |
| #include "armOMX.h" |
| #include "omxVC.h" |
| |
| #include "armVC.h" |
| #include "armCOMM_Bitstream.h" |
| #include "armCOMM.h" |
| #include "armVCM4P2_Huff_Tables_VLC.h" |
| #include "armVCM4P2_ZigZag_Tables.h" |
| |
| |
| |
| |
| /** |
| * Function: omxVCM4P2_DecodeVLCZigzag_IntraDCVLC (6.2.5.2.2) |
| * |
| * Description: |
| * Performs VLC decoding and inverse zigzag scan of AC and DC coefficients |
| * for one intra block. Two versions of the function (DCVLC and ACVLC) are |
| * provided in order to support the two different methods of processing DC |
| * coefficients, as described in [ISO14496-2], subclause 7.4.1.4, Intra DC |
| * Coefficient Decoding for the Case of Switched VLC Encoding. |
| * |
| * Input Arguments: |
| * |
| * ppBitStream - pointer to the pointer to the current byte in the |
| * bitstream buffer |
| * pBitOffset - pointer to the bit position in the current byte referenced |
| * by *ppBitStream. The parameter *pBitOffset is valid in the |
| * range [0-7]. |
| * Bit Position in one byte: |Most Least| |
| * *pBitOffset |0 1 2 3 4 5 6 7| |
| * predDir - AC prediction direction; used to select the zigzag scan |
| * pattern; takes one of the following values: |
| * - OMX_VC_NONE - AC prediction not used; |
| * performs classical zigzag scan. |
| * - OMX_VC_HORIZONTAL - Horizontal prediction; |
| * performs alternate-vertical zigzag scan; |
| * - OMX_VC_VERTICAL - Vertical prediction; |
| * performs alternate-horizontal zigzag scan. |
| * shortVideoHeader - binary flag indicating presence of |
| * short_video_header; escape modes 0-3 are used if |
| * shortVideoHeader==0, and escape mode 4 is used when |
| * shortVideoHeader==1. |
| * videoComp - video component type (luminance or chrominance) of the |
| * current block |
| * |
| * Output Arguments: |
| * |
| * ppBitStream - *ppBitStream is updated after the block is decoded such |
| * that it points to the current byte in the bit stream buffer |
| * pBitOffset - *pBitOffset is updated such that it points to the current |
| * bit position in the byte pointed by *ppBitStream |
| * pDst - pointer to the coefficient buffer of current block; must be |
| * 4-byte aligned. |
| * |
| * Return Value: |
| * |
| * OMX_Sts_NoErr - no error |
| * OMX_Sts_BadArgErr - bad arguments, if: |
| * - At least one of the following pointers is NULL: |
| * ppBitStream, *ppBitStream, pBitOffset, pDst |
| * - *pBitOffset exceeds [0,7] |
| * - preDir exceeds [0,2] |
| * - pDst is not 4-byte aligned |
| * OMX_Sts_Err - if: |
| * - In DecodeVLCZigzag_IntraDCVLC, dc_size > 12 |
| * - At least one of mark bits equals zero |
| * - Illegal stream encountered; code cannot be located in VLC table |
| * - Forbidden code encountered in the VLC FLC table. |
| * - The number of coefficients is greater than 64 |
| * |
| */ |
| |
| OMXResult omxVCM4P2_DecodeVLCZigzag_IntraDCVLC( |
| const OMX_U8 ** ppBitStream, |
| OMX_INT * pBitOffset, |
| OMX_S16 * pDst, |
| OMX_U8 predDir, |
| OMX_INT shortVideoHeader, |
| OMXVCM4P2VideoComponent videoComp |
| ) |
| { |
| /* Dummy initilaization to remove compilation error */ |
| OMX_S8 DCValueSize = 0; |
| OMX_U16 powOfSize, fetchDCbits; |
| OMX_U8 start = 1; |
| |
| /* Argument error checks */ |
| armRetArgErrIf(ppBitStream == NULL, OMX_Sts_BadArgErr); |
| armRetArgErrIf(*ppBitStream == NULL, OMX_Sts_BadArgErr); |
| armRetArgErrIf(pBitOffset == NULL, OMX_Sts_BadArgErr); |
| armRetArgErrIf(pDst == NULL, OMX_Sts_BadArgErr); |
| armRetArgErrIf(!armIs4ByteAligned(pDst), OMX_Sts_BadArgErr); |
| armRetArgErrIf((*pBitOffset < 0) || (*pBitOffset > 7), OMX_Sts_BadArgErr); |
| armRetArgErrIf((predDir > 2), OMX_Sts_BadArgErr); |
| |
| /* Insert the code into the bitstream */ |
| if (videoComp == OMX_VC_LUMINANCE) |
| { |
| DCValueSize = armUnPackVLC32(ppBitStream, |
| pBitOffset, armVCM4P2_aIntraDCLumaIndex); |
| } |
| else if (videoComp == OMX_VC_CHROMINANCE) |
| { |
| DCValueSize = armUnPackVLC32(ppBitStream, |
| pBitOffset, armVCM4P2_aIntraDCChromaIndex); |
| } |
| armRetDataErrIf(DCValueSize == -1, OMX_Sts_Err); |
| armRetDataErrIf(DCValueSize > 12, OMX_Sts_Err); |
| |
| |
| if (DCValueSize == 0) |
| { |
| pDst[0] = 0; |
| } |
| else |
| { |
| fetchDCbits = (OMX_U16) armGetBits(ppBitStream, pBitOffset, \ |
| DCValueSize); |
| |
| if ( (fetchDCbits >> (DCValueSize - 1)) == 0) |
| { |
| /* calulate pow */ |
| powOfSize = (1 << DCValueSize); |
| |
| pDst[0] = (OMX_S16) (fetchDCbits ^ (powOfSize - 1)); |
| pDst[0] = -pDst[0]; |
| } |
| else |
| { |
| pDst[0] = fetchDCbits; |
| } |
| |
| if (DCValueSize > 8) |
| { |
| /* reading and checking the marker bit*/ |
| armRetDataErrIf (armGetBits(ppBitStream, pBitOffset, 1) == 0, \ |
| OMX_Sts_Err); |
| } |
| } |
| |
| return armVCM4P2_DecodeVLCZigzag_Intra( |
| ppBitStream, |
| pBitOffset, |
| pDst, |
| predDir, |
| shortVideoHeader, |
| start); |
| } |
| |
| /* End of file */ |
| |
