SODB 数据比特串-->最原始的编码数据ide
RBSP 原始字节序列载荷-->在SODB的后面填加告终尾比特(RBSP trailing bits 一个bit“1”)若干比特“0”,以便字节对齐。编码
EBSP 扩展字节序列载荷-->在RBSP基础上填加了仿校验字节(0X03)它的缘由是: 在NALU加到Annexb上时,须要填加每组NALU以前的开始码StartCodePrefix,若是该NALU对应的slice为一帧的开始则用4位字节表示,ox00000001,不然用3位字节表示ox000001.为了使NALU主体中不包括与开始码相冲突的,在编码时,每遇到两个字节连续为0,就插入一个字节的0x03。解码时将0x03去掉。也称为脱壳操做。ip
网上查询的区别:it
在对整帧图像的数据比特串(SODB)添加原始字节序列载荷(RBSP)结尾比特(RBSP trailing bits,添加一比特的“1”和若干比特“0”,以便字节对齐)后,再检查RBSP 中是否存在连续的三字节“00000000 00000000 000000xx”;若存在这种连续的三字节码,在第三字节前插入一字节的“0×03”,以避免与起始码竞争,造成EBSP码流,这须要将近两倍的整帧图像码流大小。为了减少存储器需求,在每一个宏块编码结束后即检查该宏块SODB中的起始码竞争问题,并保留SODB最后两字节的零字节个数,以便与下一宏块的SODB的开始字节造成连续的起始码竞争检测;对一帧图像的最后一个宏块,先添加结尾中止比特,再检测起始码竞争。io
程序:ast
typedef structclass
{stream
int byte_pos; //!< current position in bitstream;基础
int bits_to_go; //!< current bitcounter扩展
byte byte_buf; //!< current buffer for last written byte
int stored_byte_pos; //!< storage for position in bitstream;
int stored_bits_to_go; //!< storage for bitcounter
byte stored_byte_buf; //!< storage for buffer of last written byte
byte byte_buf_skip; //!< current buffer for last written byte
int byte_pos_skip; //!< storage for position in bitstream;
int bits_to_go_skip; //!< storage for bitcounter
byte *streamBuffer; //!< actual buffer for written bytes
int write_flag; //!< Bitstream contains data and needs to be written
} Bitstream; 定义比特流结构
static byte *NAL_Payload_buffer;
void SODBtoRBSP(Bitstream *currStream)
{
currStream->byte_buf <<= 1; //左移1bit
currStream->byte_buf |= 1; //在尾部填一个“1”占1bit
currStream->bits_to_go--;
currStream->byte_buf <<= currStream->bits_to_go;
currStream->streamBuffer[currStream->byte_pos++] = currStream->byte_buf;
currStream->bits_to_go = 8;
currStream->byte_buf = 0;
}
int RBSPtoEBSP(byte *streamBuffer, int begin_bytepos, int end_bytepos, int min_num_bytes)
{
int i, j, count;
for(i = begin_bytepos; i < end_bytepos; i++)
NAL_Payload_buffer[i] = streamBuffer[i];
count = 0; j = begin_bytepos; for(i = begin_bytepos; i < end_bytepos; i++) { if(count == ZEROBYTES_SHORTSTARTCODE && !(NAL_Payload_buffer[i] & 0xFC)) { streamBuffer[j] = 0x03; j++; count = 0; } streamBuffer[j] = NAL_Payload_buffer[i]; if(NAL_Payload_buffer[i] == 0x00) count++; else count = 0; j++; } while (j < begin_bytepos+min_num_bytes) { streamBuffer[j] = 0x00; // cabac stuffing word streamBuffer[j+1] = 0x00; streamBuffer[j+2] = 0x03; j += 3; stat->bit_use_stuffingBits[img->type]+=16; } return j;}