JM8.6中的一个重要结构体NALU_t的定义、分配和释放

       在JM8.6中，NALU_t是一个非常重要的结构体，回寝室之前，欣赏一下结构体NALU_t的定义：

typedef struct {  int startcodeprefix_len;      //! 4 for parameter sets and first slice in picture, 3 for everything else (suggested)  unsigned len;                 //! Length of the NAL unit (Excluding the start code, which does not belong to the NALU)  unsigned max_size;            //! Nal Unit Buffer size  int nal_unit_type;            //! NALU_TYPE_xxxx  int nal_reference_idc;        //! NALU_PRIORITY_xxxx  int forbidden_bit;            //! should be always FALSE  byte *buf;        //! conjtains the first byte followed by the EBSP} NALU_t;

     接着欣赏一下AllocNALU函数

NALU_t *AllocNALU(int buffersize){  NALU_t *n;  if ((n = (NALU_t*)calloc (1, sizeof (NALU_t))) == NULL) no_mem_exit ("AllocNALU: n");  // 分配一个结构体的空间  n->max_size=buffersize;  if ((n->buf = (byte*)calloc (buffersize, sizeof (byte))) == NULL) no_mem_exit ("AllocNALU: n->buf"); // 也要分配这个空间    return n;}

      

      接着欣赏FreeNALU函数.

void FreeNALU(NALU_t *n){  if (n)  {    if (n->buf)    {      free(n->buf);  // 先释放      n->buf=NULL;       }    free (n);  // 再释放  }}

     欣赏完最后一个近似模拟程序就回去啦，如下：

#include<iostream>using namespace std;typedef struct nalu{int bufferSize;int *buf;}NALU_t;NALU_t* allocNALU(int size){NALU_t *n = new NALU_t;n->bufferSize = size;n->buf = new int[n->bufferSize];return n;}void freeNALU(NALU_t *n){if(NULL != n){if(NULL != n->buf){free(n->buf);n->buf = NULL;}free(n);n->buf = NULL;}n->bufferSize = 0;}int main(){int size = 280;NALU_t *n = allocNALU(size);int i;for(i = 0; i < size; i++){n->buf[i] = i;}for(i = 0; i < size; i++){cout << n->buf[i] << endl;}freeNALU(n);return 0;}

      Ok, 回去.

 

      第二天了. 发现还有几个函数不错呢，可以看看:

static byte *NAL_Payload_buffer;  // 文件全局变量

void FreeNalPayloadBuffer(){  if(NAL_Payload_buffer)  {    free(NAL_Payload_buffer);    NAL_Payload_buffer=NULL;  }}

void AllocNalPayloadBuffer() // 分配一帧的堆{  const int buffer_size = (input->img_width * input->img_height * 4); // AH 190202: There can be data expansion with                                                           // low QP values. So, we make sure that buffer                                                           // does not everflow. 4 is probably safe multiplier.  FreeNalPayloadBuffer();  NAL_Payload_buffer = (byte *) calloc(buffer_size, sizeof(byte));  assert (NAL_Payload_buffer != NULL);}