//

//  H264ParseSPS.c

//

//  Created by lzj<lizhijian_21@163.com> on 2018/7/6.

//  Copyright © 2018年 LZJ. All rights reserved.

//

//  See https://www.itu.int/rec/T-REC-H.264-201610-S

//



#include "H264ParseSPS.h"

#include <string.h>

#include <stdlib.h>

#include <math.h>



typedef unsigned char BYTE;

typedef int INT;

typedef unsigned int UINT;



typedef struct

{

	const BYTE *data;   //sps数据

	UINT size;          //sps数据大小

	UINT index;         //当前计算位所在的位置标记

} sps_bit_stream;



/**

移除H264的NAL防竞争码(0x03)



@param data sps数据

@param dataSize sps数据大小

*/

static void del_emulation_prevention(BYTE *data, UINT *dataSize)

{

	UINT dataSizeTemp = *dataSize;

	for (UINT i = 0, j = 0; i<(dataSizeTemp - 2); i++) {

		int val = (data[i] ^ 0x0) + (data[i + 1] ^ 0x0) + (data[i + 2] ^ 0x3);    //检测是否是竞争码

		if (val == 0) {

			for (j = i + 2; j<dataSizeTemp - 1; j++) {    //移除竞争码

				data[j] = data[j + 1];

			}



			(*dataSize)--;      //data size 减1

		}

	}

}



static void sps_bs_init(sps_bit_stream *bs, const BYTE *data, UINT size)

{

	if (bs) {

		bs->data = data;

		bs->size = size;

		bs->index = 0;

	}

}



/**

是否已经到数据流最后



@param bs sps_bit_stream数据

@return 1：yes，0：no

*/

static INT eof(sps_bit_stream *bs)

{

	return (bs->index >= bs->size * 8);    //位偏移已经超出数据

}



/**

读取从起始位开始的BitCount个位所表示的值



@param bs sps_bit_stream数据

@param bitCount bit位个数(从低到高)

@return value

*/

static UINT u(sps_bit_stream *bs, BYTE bitCount)

{

	UINT val = 0;

	for (BYTE i = 0; i<bitCount; i++) {

		val <<= 1;

		if (eof(bs)) {

			val = 0;

			break;

		}
		else if (bs->data[bs->index / 8] & (0x80 >> (bs->index % 8))) {     //计算index所在的位是否为1

			val |= 1;

		}

		bs->index++;  //递增当前起始位(表示该位已经被计算，在后面的计算过程中不需要再次去计算所在的起始位索引，缺点：后面每个bit位都需要去位移)

	}



	return val;

}



/**

读取无符号哥伦布编码值(UE)

#2^LeadingZeroBits - 1 + (xxx)



@param bs sps_bit_stream数据

@return value

*/

static UINT ue(sps_bit_stream *bs)

{

	UINT zeroNum = 0;

	while (u(bs, 1) == 0 && !eof(bs) && zeroNum < 32) {

		zeroNum++;

	}



	return (UINT)((1 << zeroNum) - 1 + u(bs, zeroNum));

}



/**

读取有符号哥伦布编码值(SE)

#(-1)^(k+1) * Ceil(k/2)



@param bs sps_bit_stream数据

@return value

*/

INT se(sps_bit_stream *bs)

{

	INT ueVal = (INT)ue(bs);

	double k = ueVal;



	INT seVal = (INT)ceil(k / 2);     //ceil:返回大于或者等于指定表达式的最小整数

	if (ueVal % 2 == 0) {       //偶数取反，即(-1)^(k+1)

		seVal = -seVal;

	}



	return seVal;

}



/**

视频可用性信息(Video usability information)解析



@param bs sps_bit_stream数据

@param info sps解析之后的信息数据及结构体

@see E.1.1 VUI parameters syntax

*/

void vui_para_parse(sps_bit_stream *bs, sps_info_struct *info)

{

	UINT aspect_ratio_info_present_flag = u(bs, 1);

	if (aspect_ratio_info_present_flag) {

		UINT aspect_ratio_idc = u(bs, 8);

		if (aspect_ratio_idc == 255) {      //Extended_SAR

			u(bs, 16);      //sar_width

			u(bs, 16);      //sar_height

		}

	}



	UINT overscan_info_present_flag = u(bs, 1);

	if (overscan_info_present_flag) {

		u(bs, 1);       //overscan_appropriate_flag

	}



	UINT video_signal_type_present_flag = u(bs, 1);

	if (video_signal_type_present_flag) {

		u(bs, 3);       //video_format

		u(bs, 1);       //video_full_range_flag

		UINT colour_description_present_flag = u(bs, 1);

		if (colour_description_present_flag) {

			u(bs, 8);       //colour_primaries

			u(bs, 8);       //transfer_characteristics

			u(bs, 8);       //matrix_coefficients

		}

	}



	UINT chroma_loc_info_present_flag = u(bs, 1);

	if (chroma_loc_info_present_flag) {

		ue(bs);     //chroma_sample_loc_type_top_field

		ue(bs);     //chroma_sample_loc_type_bottom_field

	}



	UINT timing_info_present_flag = u(bs, 1);

	if (timing_info_present_flag) {

		UINT num_units_in_tick = u(bs, 32);

		UINT time_scale = u(bs, 32);

		UINT fixed_frame_rate_flag = u(bs, 1);



		info->fps = (UINT)((float)time_scale / (float)num_units_in_tick);

		if (fixed_frame_rate_flag) {

			info->fps = info->fps / 2;

		}

	}



	UINT nal_hrd_parameters_present_flag = u(bs, 1);

	if (nal_hrd_parameters_present_flag) {

		//hrd_parameters()  //see E.1.2 HRD parameters syntax

	}



	//后面代码需要hrd_parameters()函数接口实现才有用

	UINT vcl_hrd_parameters_present_flag = u(bs, 1);

	if (vcl_hrd_parameters_present_flag) {

		//hrd_parameters()

	}

	if (nal_hrd_parameters_present_flag || vcl_hrd_parameters_present_flag) {

		u(bs, 1);   //low_delay_hrd_flag

	}



	u(bs, 1);       //pic_struct_present_flag

	UINT bitstream_restriction_flag = u(bs, 1);

	if (bitstream_restriction_flag) {

		u(bs, 1);   //motion_vectors_over_pic_boundaries_flag

		ue(bs);     //max_bytes_per_pic_denom

		ue(bs);     //max_bits_per_mb_denom

		ue(bs);     //log2_max_mv_length_horizontal

		ue(bs);     //log2_max_mv_length_vertical

		ue(bs);     //max_num_reorder_frames

		ue(bs);     //max_dec_frame_buffering

	}

}



//See 7.3.1 NAL unit syntax

//See 7.3.2.1.1 Sequence parameter set data syntax

INT h264_parse_sps(const BYTE *data, UINT dataSize, sps_info_struct *info)

{

	if (!data || dataSize <= 0 || !info) return 0;

	INT ret = 0;



	BYTE *dataBuf = (BYTE *)malloc(dataSize);

	memcpy(dataBuf, data, dataSize);        //重新拷贝一份数据，防止移除竞争码时对原数据造成影响

	del_emulation_prevention(dataBuf, &dataSize);



	sps_bit_stream bs = { 0 };

	sps_bs_init(&bs, dataBuf, dataSize);   //初始化SPS数据流结构体



	u(&bs, 1);      //forbidden_zero_bit

	u(&bs, 2);      //nal_ref_idc

	UINT nal_unit_type = u(&bs, 5);



	if (nal_unit_type == 0x7) {     //Nal SPS Flag

		info->profile_idc = u(&bs, 8);

		u(&bs, 1);      //constraint_set0_flag

		u(&bs, 1);      //constraint_set1_flag

		u(&bs, 1);      //constraint_set2_flag

		u(&bs, 1);      //constraint_set3_flag

		u(&bs, 1);      //constraint_set4_flag

		u(&bs, 1);      //constraint_set4_flag

		u(&bs, 2);      //reserved_zero_2bits

		info->level_idc = u(&bs, 8);



		ue(&bs);    //seq_parameter_set_id



		UINT chroma_format_idc = 1;     //摄像机出图大部分格式是4:2:0

		if (info->profile_idc == 100 || info->profile_idc == 110 || info->profile_idc == 122 ||

			info->profile_idc == 244 || info->profile_idc == 44 || info->profile_idc == 83 ||

			info->profile_idc == 86 || info->profile_idc == 118 || info->profile_idc == 128 ||

			info->profile_idc == 138 || info->profile_idc == 139 || info->profile_idc == 134 || info->profile_idc == 135) {

			chroma_format_idc = ue(&bs);

			if (chroma_format_idc == 3) {

				u(&bs, 1);      //separate_colour_plane_flag

			}



			ue(&bs);        //bit_depth_luma_minus8

			ue(&bs);        //bit_depth_chroma_minus8

			u(&bs, 1);      //qpprime_y_zero_transform_bypass_flag

			UINT seq_scaling_matrix_present_flag = u(&bs, 1);

			if (seq_scaling_matrix_present_flag) {

				UINT seq_scaling_list_present_flag[8] = { 0 };

				for (INT i = 0; i<((chroma_format_idc != 3) ? 8 : 12); i++) {

					seq_scaling_list_present_flag[i] = u(&bs, 1);

					if (seq_scaling_list_present_flag[i]) {

						if (i < 6) {    //scaling_list(ScalingList4x4[i], 16, UseDefaultScalingMatrix4x4Flag[i])

						}
						else {    //scaling_list(ScalingList8x8[i − 6], 64, UseDefaultScalingMatrix8x8Flag[i − 6] )

						}

					}

				}

			}

		}



		ue(&bs);        //log2_max_frame_num_minus4

		UINT pic_order_cnt_type = ue(&bs);

		if (pic_order_cnt_type == 0) {

			ue(&bs);        //log2_max_pic_order_cnt_lsb_minus4

		}
		else if (pic_order_cnt_type == 1) {

			u(&bs, 1);      //delta_pic_order_always_zero_flag

			se(&bs);        //offset_for_non_ref_pic

			se(&bs);        //offset_for_top_to_bottom_field



			UINT num_ref_frames_in_pic_order_cnt_cycle = ue(&bs);

			INT *offset_for_ref_frame = (INT *)malloc((UINT)num_ref_frames_in_pic_order_cnt_cycle * sizeof(INT));

			for (INT i = 0; i<num_ref_frames_in_pic_order_cnt_cycle; i++) {

				offset_for_ref_frame[i] = se(&bs);

			}

			free(offset_for_ref_frame);

		}



		ue(&bs);      //max_num_ref_frames

		u(&bs, 1);      //gaps_in_frame_num_value_allowed_flag



		UINT pic_width_in_mbs_minus1 = ue(&bs);     //第36位开始

		UINT pic_height_in_map_units_minus1 = ue(&bs);      //47

		UINT frame_mbs_only_flag = u(&bs, 1);



		info->width = (INT)(pic_width_in_mbs_minus1 + 1) * 16;

		info->height = (INT)(2 - frame_mbs_only_flag) * (pic_height_in_map_units_minus1 + 1) * 16;



		if (!frame_mbs_only_flag) {

			u(&bs, 1);      //mb_adaptive_frame_field_flag

		}



		u(&bs, 1);     //direct_8x8_inference_flag

		UINT frame_cropping_flag = u(&bs, 1);

		if (frame_cropping_flag) {

			UINT frame_crop_left_offset = ue(&bs);

			UINT frame_crop_right_offset = ue(&bs);

			UINT frame_crop_top_offset = ue(&bs);

			UINT frame_crop_bottom_offset = ue(&bs);



			//See 6.2 Source, decoded, and output picture formats

			INT crop_unit_x = 1;

			INT crop_unit_y = 2 - frame_mbs_only_flag;      //monochrome or 4:4:4

			if (chroma_format_idc == 1) {   //4:2:0

				crop_unit_x = 2;

				crop_unit_y = 2 * (2 - frame_mbs_only_flag);

			}
			else if (chroma_format_idc == 2) {    //4:2:2

				crop_unit_x = 2;

				crop_unit_y = 2 - frame_mbs_only_flag;

			}



			info->width -= crop_unit_x * (frame_crop_left_offset + frame_crop_right_offset);

			info->height -= crop_unit_y * (frame_crop_top_offset + frame_crop_bottom_offset);

		}



		UINT vui_parameters_present_flag = u(&bs, 1);

		if (vui_parameters_present_flag) {

			vui_para_parse(&bs, info);

		}



		ret = 1;

	}

	free(dataBuf);



	return ret;

}