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从文件中读取yuv和h264数据

时间:09-27来源:作者:点击数:29

参考ffmpeg avc.c写的从文件中一帧帧读取h.264数据的demo

  • #include <stdio.h>
  • #include <stdlib.h>
  • #include <stddef.h>
  • #include <string.h>
  • char* filebuf_;
  • const char* pbuf_;
  • int filesize_;
  • unsigned char is_stop_;
  • const char* AVCFindStartCodeInternal(const char *p, const char *end)
  • {
  • const char *a = p + 4 - ((ptrdiff_t)p & 3);
  • for (end -= 3; p < a && p < end; p++) {
  • if (p[0] == 0 && p[1] == 0 && p[2] == 1)
  • return p;
  • }
  • for (end -= 3; p < end; p += 4) {
  • unsigned int x = *(const unsigned int*)p;
  • // if ((x - 0x01000100) & (~x) & 0x80008000) // little endian
  • // if ((x - 0x00010001) & (~x) & 0x00800080) // big endian
  • if ((x - 0x01010101) & (~x) & 0x80808080) { // generic
  • if (p[1] == 0) {
  • if (p[0] == 0 && p[2] == 1)
  • return p;
  • if (p[2] == 0 && p[3] == 1)
  • return p + 1;
  • }
  • if (p[3] == 0) {
  • if (p[2] == 0 && p[4] == 1)
  • return p + 2;
  • if (p[4] == 0 && p[5] == 1)
  • return p + 3;
  • }
  • }
  • }
  • for (end += 3; p < end; p++) {
  • if (p[0] == 0 && p[1] == 0 && p[2] == 1)
  • return p;
  • }
  • return end + 3;
  • }
  • const char* AVCFindStartCode(const char *p, const char *end)
  • {
  • const char *out = AVCFindStartCodeInternal(p, end);
  • if (p<out && out<end && !out[-1]) out--;
  • return out;
  • }
  • H264FrameReader_Init(const char* filename)
  • {
  • FILE* fp = fopen(filename, "rb");
  • filebuf_ = 0;
  • filesize_ = 0;
  • if (fp)
  • {
  • int retval = 0;
  • fseek(fp, 0, SEEK_END);
  • filesize_ = ftell(fp);
  • fseek(fp, 0, SEEK_SET);
  • filebuf_ = (char*)malloc(filesize_);
  • retval = fread(filebuf_, 1, filesize_, fp);
  • fclose(fp);
  • }
  • pbuf_ = filebuf_;
  • }
  • H264FrameReader_Free()
  • {
  • free(filebuf_);
  • }
  • H264FrameReader_ReadFrame(char* outBuf, int* outBufSize)
  • {
  • char* pbufout = 0;
  • const char *p = 0;
  • const char *end = 0;
  • const char *nal_start, *nal_end;
  • char startcodebuf[] = { 0x00, 0x00, 0x00, 0x01 };
  • if (pbuf_ >= filebuf_ + filesize_)
  • {
  • return 0;
  • }
  • pbufout = outBuf;
  • p = pbuf_;
  • end = filebuf_ + filesize_;
  • nal_start = AVCFindStartCode(p, end);
  • while (nal_start < end)
  • {
  • unsigned int nal_size = 0;
  • unsigned char nal_type = 0;
  • while (!*(nal_start++));
  • nal_end = AVCFindStartCode(nal_start, end);
  • nal_size = nal_end - nal_start;
  • nal_type = nal_start[0] & 0x1f;
  • memcpy(pbufout, startcodebuf, 4);
  • pbufout += 4;
  • memcpy(pbufout, nal_start, nal_size);
  • pbufout += nal_size;
  • nal_start = nal_end;
  • break;
  • }
  • *outBufSize = pbufout - outBuf;
  • pbuf_ = nal_start;
  • return 1;
  • }
  • int main(int argc, char **argv)
  • {
  • unsigned long max_size = 1280 * 720;
  • int tmpbuf_len = 0;
  • int current_read_len = 0;
  • char* tmpbuf = (char*)malloc(max_size * 10);
  • FILE *fp = fopen("out.h264", "wb+");
  • if (!fp)
  • {
  • printf("open file error\n");
  • return -1;
  • }
  • H264FrameReader_Init("test.h264");
  • printf("file size = %d\n", filesize_);
  • while (current_read_len < filesize_)
  • {
  • if (H264FrameReader_ReadFrame(tmpbuf, &tmpbuf_len))
  • {
  • printf("tmpbuf_len = %d\n", tmpbuf_len);
  • fwrite(tmpbuf, tmpbuf_len, 1, fp);
  • current_read_len += tmpbuf_len;
  • }
  • }
  • fclose(fp);
  • H264FrameReader_Free();
  • return 0;
  • }

2.从文件中读取yuv数据

从planar yuv420 文件中读取每一帧数据,从nvenc demo中参考来的,原理如下

1.通过fseek和ftell计算出文件的大小

2.通过yuv的分辨率可以计算出每一帧yuv数据的大小

3.通过上面两步可以计算出文件中包含多少帧的yuv数据,然后通过每一帧数据在文件中的偏移,就可以读出该帧数据

  • int loadframe(uint8_t *yuvInput[3], FILE *hInputYUVFile, uint32_t frmIdx, uint32_t width, uint32_t height)
  • {
  • uint64_t fileOffset;
  • uint32_t result;
  • uint32_t dwInFrameSize = 0;
  • int anFrameSize[3] = {};
  • dwInFrameSize = width * height * 3 / 2;
  • anFrameSize[0] = width * height;
  • anFrameSize[1] = anFrameSize[2] = width * height / 4;
  • //当前帧在文件中的偏移量:当前index * 每一帧的大小
  • fileOffset = (uint64_t)dwInFrameSize * frmIdx;
  • //seek到偏移处
  • result = _fseeki64(hInputYUVFile, fileOffset, SEEK_SET);
  • if (result == -1)
  • {
  • return -1;
  • }
  • //把当前帧的Y、U、V数据分别读取到对应的数组中
  • fread(yuvInput[0], anFrameSize[0], 1, hInputYUVFile);
  • fread(yuvInput[1], anFrameSize[1], 1, hInputYUVFile);
  • fread(yuvInput[2], anFrameSize[2], 1, hInputYUVFile);
  • return 0;
  • }
  • int main()
  • {
  • infp = fopen("yb.yuv", "rb");
  • if (!infp)
  • {
  • printf("open in file failed\n");
  • return -1;
  • }
  • uint8_t *yuv[3];
  • int lumaPlaneSize, chromaPlaneSize;
  • lumaPlaneSize = 1920 * 1080;
  • chromaPlaneSize = lumaPlaneSize >> 2;
  • yuv[0] = new uint8_t[lumaPlaneSize];
  • yuv[1] = new uint8_t[chromaPlaneSize];
  • yuv[2] = new uint8_t[chromaPlaneSize];
  • memset(yuv[0], 0, lumaPlaneSize);
  • memset(yuv[1], 0, chromaPlaneSize);
  • memset(yuv[2], 0, chromaPlaneSize);
  • uint64_t file_size = 0;
  • _fseeki64(infp, 0, SEEK_END);
  • file_size = _ftelli64(infp);
  • _fseeki64(infp, 0, SEEK_SET);
  • int totalFrames = file_size / (lumaPlaneSize + chromaPlaneSize + chromaPlaneSize);
  • //遍历每一帧YUV数据
  • for (int frm = 0; frm < totalFrames; frm++)
  • {
  • loadframe(yuv, infp, frm, 1920, 1080);
  • //处理yuv数据
  • //....
  • }
  • return 0;
  • }
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