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193 lines
7.4 KiB
193 lines
7.4 KiB
/******************************************************************************
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*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*****************************************************************************
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* Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore
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*/
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/**
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*******************************************************************************
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* @file
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* ih264e_globals.h
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*
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* @brief
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* Contains declarations of global variables for H264 encoder
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*
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* @author
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* Ittiam
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*
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* @remarks
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*
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*******************************************************************************
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*/
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#ifndef IH264E_GLOBALS_H_
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#define IH264E_GLOBALS_H_
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/*****************************************************************************/
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/* Extern global declarations */
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/*****************************************************************************/
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/**
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******************************************************************************
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* @brief Computes the lamda for varying quantizer scales that would be used to
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* compute the RD cost while deciding on the MB modes.
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* input : qp
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* output : lambda
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* @remarks lambda = 0.85 * pow(2, (qp - 12)/3), when SSD is used as metric
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* for computing distortion (Bit rate estimation for cost function of H.264/
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* AVC by Mohd Golam Sarwer et. al.) If the use of distortion metric is SAD
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* rather than SSD in the stage of encoding, consider sqrt(lambda) simply to
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* adjust lambda for the lack of squaring operation in the error computation
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* (from rate distortion optimization for video compression by sullivan).
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******************************************************************************
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*/
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extern const UWORD16 gu2_qp_lambda[52];
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/**
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******************************************************************************
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* @brief Computes the lamda for varying quantizer scales that would be used to
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* compute the RD cost while deciding on the MB modes.
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* input : qp
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* output : lambda
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* @remarks lambda = pow(2, (qp - 12)/6). When Lagrangian multiplier is disabled
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* the same constant is used across mode decision and mv decisions.
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******************************************************************************
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*/
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extern const UWORD8 gu1_qp0[52];
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/**
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******************************************************************************
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* @brief unsigned exp. goulumb codelengths to assign cost to a coefficient of
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* mb types.
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* input : Integer
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* output : codelength
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* @remarks Refer sec. 9-1 in h264 specification
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******************************************************************************
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*/
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extern const UWORD8 u1_uev_codelength[32];
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/**
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******************************************************************************
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* @brief Look up table to assign cost to a coefficient of a residual block
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* basing on its surrounding coefficients
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* input : Numbers of T1's
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* output : coeff_cost
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* @remarks Refer Section 2.3 Elimination of single coefficients in inter
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* macroblocks in document JVT-O079
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******************************************************************************
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*/
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extern const UWORD8 gu1_coeff_cost[6];
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/**
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******************************************************************************
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* @brief Indices map to raster scan for luma 4x4 block
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* input : scan index
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* output : scan location
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* @remarks The scan order assumes the stride to access the next row is 16
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******************************************************************************
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*/
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extern const UWORD8 gu1_luma_scan_order[16];
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/**
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******************************************************************************
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* @brief Indices map to raster scan for chroma AC block
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* input : scan index
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* output : scan location
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* @remarks The scan order assumes the stride to access the next row is 32
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******************************************************************************
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*/
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extern const UWORD8 gu1_chroma_scan_order[15];
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/**
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******************************************************************************
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* @brief Indices map to raster scan for luma 4x4 dc block
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* input : scan index
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* output : scan location
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* @remarks The scan order assumes the stride to access the next row is 16
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******************************************************************************
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*/
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extern const UWORD8 gu1_luma_scan_order_dc[16];
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/**
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******************************************************************************
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* @brief Indices map to raster scan for chroma 2x2 dc block
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* input : scan index
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* output : scan location
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* @remarks The scan order assumes the stride to access the next row is 16
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******************************************************************************
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*/
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extern const UWORD8 gu1_chroma_scan_order_dc[4];
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/**
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******************************************************************************
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* @brief choice of motion vectors to be used during mv prediction
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* input : formatted reference idx comparison metric
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* output : mv prediction has to be median or a simple straight forward selec
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* tion from neighbors.
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* @remarks If only one of the candidate blocks has a reference frame equal to
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the current block then use the same block as the final predictor. A simple
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look up table to assist this mv prediction condition
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******************************************************************************
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*/
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extern const WORD8 gi1_mv_pred_condition[8];
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/**
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******************************************************************************
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* @brief maps the h264 quantizer to the mpeg2 quantizer scale
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* input : h264 qp
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* output : eqvivalent mpeg 2 qp
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* @remarks mpeg2qscale = 2 ^ [((h264qp - 12) / 6) + 1]
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******************************************************************************
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*/
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extern const UWORD8 gau1_h264_to_mpeg2_qmap[H264_QP_ELEM];
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/**
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******************************************************************************
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* @brief maps the mpeg2 quantizer to the h264 quantizer scale
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* input : mpeg2 qp
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* output : eqvivalent h264q p
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* @remarks MPEG-2 dequantization: (2*QFij + k)*Wij*qscale/32
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* k = 0 (for intra) k = sign(QFij)
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* H.264 dequantization: (QFij*R(QP%6,i,j))>>(6 - QP/6)
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*
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* Excluding the portion of R(QP%6,i,j) that is due to
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* the DCT scale factors, the 6 entries after dividing by 64 (2^6)
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* correspond to dequant values of
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* 2.5, 2.8125, 3.125, 3.5625, 3.9375, 4.4375.
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* (a=0.5 b=sqrt(2/5) - refer to JVT-B038.doc)
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*
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* Assuming that h264Qp=12 corresponds to MPEG2 qscale of 2
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* (the actual mapping seems to be to MPEG2 qscale of 2.5),
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* and the fact that the effective h264 quantizer changes by
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* a factor of 2 for every 6 steps, the following mapping is
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* obtained:
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* h264qp = 6*(log2(mpeg2qscale/2)) + 12.
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*
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* Note that the quant matrix entry assumed for the above
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* equality is 16. Hence when the mpeg2 quant matrix entries
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* are all 16, this lookup can be used as is (which is the
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* default inter quant matrix in mpeg-2).
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******************************************************************************
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*/
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extern const UWORD8 gau1_mpeg2_to_h264_qmap[MPEG2_QP_ELEM];
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#endif /* IH264E_GLOBALS_H_ */
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