H264相关

001

bool

UDPReceiver::getResolution(

int

channel,

int

&Width,

int

& Height)

002

{

003

BYTE

*buf =

new

BYTE

[1024];

004

int

nLen;

005

AVPacket packet;

006

BOOL

bSpsComplete = FALSE;

007

// Find SPS

008

while

(!bSpsComplete)

009

{

010

int

ret = av_read_frame(m_pFormatContext[channel], &packet);

011

if

(packet.flags & AV_PKT_FLAG_KEY)

012

{

013

BYTE

* p = packet.data;

014

BYTE

last_nal_type = 0;

015

int

last_nal_pos = 0;

016

for

(

int

i=0; i<packet.size-5; i++)

017

{

018

p = packet.data + i;

019

if

(p[0]==0x00&&p[1]==0x00&&p[2]==0x00&&p[3]==0x01)

020

{

021

if

(last_nal_type == 0x67)

022

{

023

nLen = i-last_nal_pos;

024

memcpy

(buf, packet.data+last_nal_pos, nLen);

025

bSpsComplete = TRUE;

026

}

027

last_nal_type = p[4];

028

last_nal_pos = i;

029

if

(bSpsComplete)

030

{

031

break

;

032

}

033

}

034

}

035

if

(last_nal_type == 0x67 && bSpsComplete == FALSE)

036

{

037

nLen = packet.size - last_nal_pos;

038

memcpy

(buf, packet.data+last_nal_pos, nLen);

039

bSpsComplete = TRUE;

040

}

041

}

042

}

043

// Analyze SPS to find width and height

044

UINT

StartBit=0; 

045

buf = buf + 4;

046

int

forbidden_zero_bit=u(1,buf,StartBit);

047

int

nal_ref_idc=u(2,buf,StartBit);

048

int

nal_unit_type=u(5,buf,StartBit);

049

if

(nal_unit_type==7)

050

{

051

int

profile_idc=u(8,buf,StartBit);

052

int

constraint_set0_flag=u(1,buf,StartBit);

//(buf[1] & 0x80)>>7;

053

int

constraint_set1_flag=u(1,buf,StartBit);

//(buf[1] & 0x40)>>6;

054

int

constraint_set2_flag=u(1,buf,StartBit);

//(buf[1] & 0x20)>>5;

055

int

constraint_set3_flag=u(1,buf,StartBit);

//(buf[1] & 0x10)>>4;

056

int

reserved_zero_4bits=u(4,buf,StartBit);

057

int

level_idc=u(8,buf,StartBit);

058

059

int

seq_parameter_set_id=Ue(buf,nLen,StartBit);

060

061

if

( profile_idc == 100 || profile_idc == 110 ||

062

profile_idc == 122 || profile_idc == 144 )

063

{

064

int

chroma_format_idc=Ue(buf,nLen,StartBit);

065

if

( chroma_format_idc == 3 )

066

int

residual_colour_transform_flag=u(1,buf,StartBit);

067

int

bit_depth_luma_minus8=Ue(buf,nLen,StartBit);

068

int

bit_depth_chroma_minus8=Ue(buf,nLen,StartBit);

069

int

qpprime_y_zero_transform_bypass_flag=u(1,buf,StartBit);

070

int

seq_scaling_matrix_present_flag=u(1,buf,StartBit);

071

072

int

seq_scaling_list_present_flag[8];

073

if

( seq_scaling_matrix_present_flag )

074

{

075

for

(

int

i = 0; i < 8; i++ ) {

076

seq_scaling_list_present_flag[i]=u(1,buf,StartBit);

077

}

078

}

079

}

080

int

log2_max_frame_num_minus4=Ue(buf,nLen,StartBit);

081

int

pic_order_cnt_type=Ue(buf,nLen,StartBit);

082

if

( pic_order_cnt_type == 0 )

083

int

log2_max_pic_order_cnt_lsb_minus4=Ue(buf,nLen,StartBit);

084

else

if

( pic_order_cnt_type == 1 )

085

{

086

int

delta_pic_order_always_zero_flag=u(1,buf,StartBit);

087

int

offset_for_non_ref_pic=Se(buf,nLen,StartBit);

088

int

offset_for_top_to_bottom_field=Se(buf,nLen,StartBit);

089

int

num_ref_frames_in_pic_order_cnt_cycle=Ue(buf,nLen,StartBit);

090

091

int

*offset_for_ref_frame=

new

int

[num_ref_frames_in_pic_order_cnt_cycle];

092

for

(

int

i = 0; i < num_ref_frames_in_pic_order_cnt_cycle; i++ )

093

offset_for_ref_frame[i]=Se(buf,nLen,StartBit);

094

delete

[] offset_for_ref_frame;

095

}

096

int

num_ref_frames=Ue(buf,nLen,StartBit);

097

int

gaps_in_frame_num_value_allowed_flag=u(1,buf,StartBit);

098

int

pic_width_in_mbs_minus1=Ue(buf,nLen,StartBit);

099

int

pic_height_in_map_units_minus1=Ue(buf,nLen,StartBit);

100

101

Width=(pic_width_in_mbs_minus1+1)*16;

102

Height=(pic_height_in_map_units_minus1+1)*16;

103

104

return

true

;

105

}

106

else

107

{

108

return

false

;

109

}

110

}

111

112

// Ue find the num of zeros and get (num+1) bits from the first 1, and 

113

// change it to decimal

114

// e.g. 00110 -> return 6(110)

115

UINT

UDPReceiver::Ue(

BYTE

*pBuff,

UINT

nLen,

UINT

&nStartBit)

116

{

117

//计算0bit的个数

118

UINT

nZeroNum = 0;

119

while

(nStartBit < nLen * 8)

120

{

121

if

(pBuff[nStartBit / 8] & (0x80 >> (nStartBit % 8)))

//&:按位与，%取余

122

{

123

break

;

124

}

125

nZeroNum++;

126

nStartBit++;

127

}

128

nStartBit ++;

129

130

131

//计算结果

132

DWORD

dwRet = 0;

133

for

(

UINT

i=0; i<nZeroNum; i++)

134

{

135

dwRet <<= 1;

136

if

(pBuff[nStartBit / 8] & (0x80 >> (nStartBit % 8)))

137

{

138

dwRet += 1;

139

}

140

nStartBit++;

141

}

142

return

(1 << nZeroNum) - 1 + dwRet;

143

}

144

145

int

UDPReceiver::Se(

BYTE

*pBuff,

UINT

nLen,

UINT

&nStartBit)

146

{

147

int

UeVal=Ue(pBuff,nLen,nStartBit);

148

double

k=UeVal;

149

int

nValue=std::

ceil

(k/2);

//ceil函数：ceil函数的作用是求不小于给定实数的最小整数。ceil(2)=ceil(1.2)=cei(1.5)=2.00

150

if

(UeVal % 2==0)

151

nValue=-nValue;

152

return

nValue;

153

}

154

155

// u Just returns the BitCount bits of buf and change it to decimal.

156

// e.g. BitCount = 4, buf = 01011100, then return 5(0101)

157

DWORD

UDPReceiver::u(

UINT

BitCount,

BYTE

* buf,

UINT

&nStartBit)

158

{

159

DWORD

dwRet = 0;

160

for

(

UINT

i=0; i<BitCount; i++)

161

{

162

dwRet <<= 1;

163

if

(buf[nStartBit / 8] & (0x80 >> (nStartBit % 8)))

164

{

165

dwRet += 1;

166

}

167

nStartBit++;

168

}

169

return

dwRet;

170

}