"H.264 / AVC Video Code Technology Detailed" video tutorial has been on "CSDN", which details the background, standard protocol and implementation of H.264, and through a practical engineering form to H.264 Standard analysis and implementation, welcome to watch!
"The paper is very shallow, perceived this matter", only the standard document is operated in the form of code, in order to have a sufficient understanding and understanding of the video compression coding standards!
Link address: H.264 / AVC video codec technology detailed
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H.264 syntax element after the encoding, to generate output data are encapsulated NAL Unit is passed, the data combining together to form a plurality of NAL Unit of total output stream. For different application scenarios, NAL different predetermined format adapted to transmit a common package type. NAL Unit is usually divided into two types of transmission formats: RTP packet format and the byte stream format;
Byte stream format: byte stream format specified in Annex B of the H.264 standard protocol documents, most of the default output format encoder implementation. Byte stream format transmitted in the form of a continuous bit stream of bytes, must be obtained from the code stream NAL Unit. The method of identification is an identification code of the NAL Unit code stream: 0x00 00 00 01 or 0x 00 00 01. The series is based H.264 stream using a stream-based format. RTP packet format: NAL Unit Packet Format The Format Encapsulated method according to RTP packets. RTP packet format using no additional segmentation identification code, data length information corresponding to the information in the RTP packet encapsulation. This package format is not clearly defined in the standard protocol documents, but do some processing JM Decoder in. Usually represented by the length of the whole length of the NAL Unit with a fixed length code at the start of the NAL Unit.
H.264 code stream format stream structure shown below: NAL Unit byte stream format:
leading_zero_8bits: before the first 0 byte prefix NAL unit; zero_byte: a character byte 0; start_code_prefix_one_3bytes: 3-character prefix starting symbol, the value of 0x 00 00 01, and together constitute a zero_byte 0x 00 00 0001 prefix character; nal_unit: Unit represents a bit of NAL; trailing_zero_8bits: 0 end characters;
For H.264 stream format byte stream read from the code stream NAL Unit method to detect data between 0x 00 00 01 or two 0x 00 00 00 01 start code.
The following presents a simple procedure to extract NAL UNIT Reference:
// FindNALContent.cpp: custom console application entry point.
//
#include "stdafx.h"
typedef unsigned char uint8;
Using namespace std;
static int find_nal_prefix (FILE ** pFileIn, vector
& nalBytes)
{
FILE * pFile = * pFileIn;
/ *
00 00 00 01 x x x x x x 00 00 00 01
* /
uint8 prefix [3] = {0};
uint8 fileByte;
/ *
[0] [1] [2] = {0 0 0} -> [1] [2] [0]} = {0 0 0 -.1882 [2] [0] [1] = {0 00}
getc () = 1 -> 0 0 0 1
[0] [1] [2] = {0 0 1} -> [1] [2] [0] = {0 0 1} -> [2] [0] [1] = {0 01}
* /
nalBytes.clear ();
int pos = 0, getPrefix = 0;
for (int idx = 0;. idx .1881 3; idx ++)
{
prefix [idx] = getc (pFile);
nalBytes.push_back (prefix [idx]);
}
while (! feof (pFile))
{
if ((prefix [pos% 3] == 0) && (prefix [(pos + 1)% 3] == 0) && (prefix [(pos + 2)% 3] == 1))
{
// 0x 00 00 01 found
getPrefix = 1;
nalBytes.pop_back ();
nalBytes.pop_back ();
nalBytes.pop_back ();
Break;
}
else if ((prefix [pos% 3] == 0) && (prefix [(pos + 1)% 3] == 0) && (prefix [(pos + 2)% 3] == 0))
{
if (1 == getc (pFile))
{
// 0x 00 00 00 01 found
getPrefix = 2;
nalBytes.pop_back ();
nalBytes.pop_back ();
nalBytes.pop_back ();
Break;
}
}
Else
{
fileByte = getc (pFile);
prefix [(pos ++)% 3] = fileByte;
nalBytes.push_back (fileByte);
}
}
return getPrefix;
}
int _tmain (int argc, _TCHAR * argv [])
{
FILE * pFile_in = NULL;
_tfopen_s (& pFile_in, argv [1], _T ( "rb"));
if (! pFile_in)
{
printf ( "Error: Opening input file failed \ n.");
}
. Vector
