3516熟悉ffmpeg的看过来，avformat_alloc_context为什么会出错_问答

我编译了ffmpeg的最小库，自己写了一个测试程序本来就没有几行代码，在板子上运行

/*Include ffmpeg header file*/
#include
#include
#include
#include
#include
#include
#include

void main()
{
//变量
AVFormatContext *pFormatCtx = NULL;
//const char rtspUrl[] = "rtsp://172.16.3.119/live/stream0";
AVPacket *packet;
int i =0,j = 0,m =0;
//初始化
printf("Test ffmpeg  2019 0716 1\n");
av_register_all();
printf("Test ffmpeg  1.1\n");
avformat_network_init();
printf("Test ffmpeg  1.2\n");
pFormatCtx = avformat_alloc_context();
printf("Test ffmpeg  1.3\n");

av_free(pFormatCtx);
//av_free(packet);
}

红色部份报错，Test ffmpeg  1.2都可以打印，实在是分析不出来了，我的板子flash空间只有1M多，内存空间只有3M
不知道这个有没有影响，avformat_alloc_context()这个申请的内存空间到底是多大啊

AVFormatContext *avformat_alloc_context(void)
{
AVFormatContext *ic;
ic = av_malloc(sizeof(AVFormatContext));
if (!ic)

      return ic;
avformat_get_context_defaults(ic);

ic->internal = av_mallocz(sizeof(*ic->internal));
if (!ic->internal) {
      avformat_free_context(ic);
      return NULL;
}

return ic;
}

static size_t max_alloc_size= INT_MAX;

//INT_MAX定义在limits.h头文件中，具体的数没必要记住，只要知道是很大的就行了！

//好像c中32位的int的范围是：-2147483648->2147483647.

void *av_malloc(size_t size)
{
void *ptr = NULL;
#if CONFIG_MEMALIGN_HACK//这都是定义在config.h中的。初始定义为0
long diff;
#endif

/* let's disallow possibly ambiguous cases */
if (size > (max_alloc_size - 32))
      return NULL;

#if CONFIG_MEMALIGN_HACK
ptr = malloc(size + ALIGN);//ALIGN=32
if (!ptr)
      return ptr;//一般会走到这里就结束了
diff             = ((~(long)ptr)&(ALIGN - 1)) + 1;
ptr             = (char *)ptr + diff;
((char *)ptr)[-1] = diff;
#elif HAVE_POSIX_MEMALIGN
if (size) //OS X on SDK 10.6 has a broken posix_memalign implementation
if (posix_memalign(&ptr, ALIGN, size))
      ptr = NULL;
#elif HAVE_ALIGNED_MALLOC
ptr = _aligned_malloc(size, ALIGN);
#elif HAVE_MEMALIGN
#ifndef __DJGPP__
ptr = memalign(ALIGN, size);
#else
ptr = memalign(size, ALIGN);
#endif
/* Why 64?
   * Indeed, we should align it:
   * on  4 for 386
   * on 16 for 486
   * on 32 for 586, PPro - K6-III
   * on 64 for K7 (maybe for P3 too).
   * Because L1 and L2 caches are aligned on those values.
   * But I don't want to code such logic here!
   */
/* Why 32?
   * For AVX ASM. SSE / NEON needs only 16.
   * Why not larger? Because I did not see a difference in benchmarks ...
   */
/* benchmarks with P3
   * memalign(64) + 1       3071, 3051, 3032
   * memalign(64) + 2       3051, 3032, 3041
   * memalign(64) + 4       2911, 2896, 2915
   * memalign(64) + 8       2545, 2554, 2550
   * memalign(64) + 16       2543, 2572, 2563
   * memalign(64) + 32       2546, 2545, 2571
   * memalign(64) + 64       2570, 2533, 2558
   *
   * BTW, malloc seems to do 8-byte alignment by default here.
   */
#else
ptr = malloc(size);
#endif
if(!ptr && !size) {
      size = 1;
      ptr= av_malloc(1);
}
#if CONFIG_MEMORY_POISONING
if (ptr)
      memset(ptr, FF_MEMORY_POISON, size);
#endif
return ptr;
}

3516熟悉ffmpeg的看过来，avformat_alloc_context为什么会出错

Markdown 语法

Markdown 语法