读取笔记本的摄像头的原始yuv数据,通过libav(ffmpeg编码)

最新推荐文章于 2024-06-28 20:04:19 发布

wishfly

最新推荐文章于 2024-06-28 20:04:19 发布

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本文介绍了如何利用uvccapture库获取摄像头的YUYV格式原始数据，然后通过libav库将这些数据转换为H.264编码的yuv数据，并最终将编码后的视频流保存到文件中。详细步骤包括初始化设备、设置编码参数、读取数据、编码并写入文件。此外，提供了关键代码片段及编译指令，便于读者实践。

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一、程序的逻辑主要分两部分：

1、通过video4linux2读取摄像头的V4L2_PIX_FMT_YUYV格式的原始数据

2、把V4L2_PIX_FMT_YUYV格式的数据转换成AV_PIX_FMT_YUV422P格式的yuv数据，并存放在AVFrame结构中；把AVFrame结构送到编码器；

收取编码后的h264数据流，并存到文件中

二、代码中主要用到的库：

1、通过一个叫uvccapture-0.5库（我直接改了里面的代码），获取摄像头的V4L2_PIX_FMT_YUYV格式数据。

2、通过libav编码

三、主要代码：

/*
 * main.cpp
 *
 *  Created on: 2014-3-2
 *      Author: xy
 */

#include 
#include 
#include 
#include 
#include 
//ffplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0
#ifdef __cplusplus
extern "C" {
#endif
#define __STDC_CONSTANT_MACROS
#ifdef _STDINT_H
#undef _STDINT_H
#endif
# include 
#include "libavformat/avformat.h"
#include "libavdevice/avdevice.h"
#include 
#include 

#ifdef __cplusplus
}
#endif
//输入设备
#include "v4l2uvc.h"
int main() {
  //v4l2 val
  char *videodevice = "/dev/video0";
  int width = 640; //320;
  int height = 480; //240;
  int brightness = 0, contrast = 0, saturation = 0, gain = 0;
  int quality = 95;
  int format = V4L2_PIX_FMT_YUYV;
  struct vdIn *videoIn;
  int grabmethod = 1;

  //video encoder init
  avcodec_register_all();

  AVCodec *codec;
  AVCodecContext *c = NULL;
  int i, ret, x, y, got_output;
  FILE *f;
  AVFrame *frame;
  AVPacket pkt;
  uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  char filename[] = "test.264";
  printf("Encode video file %s\n", filename);

  /* find the mpeg1 video encoder */
  codec = avcodec_find_encoder(AV_CODEC_ID_H264);
  if (!codec) {
    fprintf(stderr, "Codec not found\n");
    exit(1);
  }
  c = avcodec_alloc_context3(codec);
  if (!c) {
    fprintf(stderr, "Could not allocate video codec context\n");
    exit(1);
  }
  /* put sample parameters */
  c->bit_rate = 400000;
  /* resolution must be a multiple of two */
  c->width = width; // 352;
  c->height = height; // 288;
  /* frames per second */
  c->time_base = (AVRational) {1,10/*25*/};
  c->gop_size = 10; /* emit one intra frame every ten frames */
  c->max_b_frames = 0; //1
  c->pix_fmt = AV_PIX_FMT_YUV422P; //v4l2是这个格式  AV_PIX_FMT_YUV420P;

  //av_opt_set(c->priv_data, "preset", "slow", 0);
  av_opt_set(c->priv_data, "tune", "zerolatency", 0); //这个可以让libav不缓存视频帧
      /********************************************************************************
       * 有两个地方影响libav是不是缓存编码后的视频帧，也就是影响实时性：
       * 1、av_opt_set(c->priv_data, "tune", "zerolatency", 0);这个比较主要。
       * 2、参数中有c->max_b_frames = 1;如果这个帧设为0,就没有B帧了，编码会很快的。
       ********************************************************************************/

  /* open it */
  if (avcodec_open2(c, codec, NULL) < 0) {
    fprintf(stderr, "Could not open codec\n");
    exit(1);
  }

  f = fopen(filename, "wb");
  if (!f) {
    fprintf(stderr, "Could not open %s\n", filename);
    exit(1);
  }

  frame = av_frame_alloc();
  if (!frame) {
    fprintf(stderr, "Could not allocate video frame\n");
    exit(1);
  }
  frame->format = c->pix_fmt;
  frame->width = c->width;
  frame->height = c->height;

  /* the image can be allocated by any means and av_image_alloc() is
   * just the most convenient way if av_malloc() is to be used */
  ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height,
      c->pix_fmt, 32);
  if (ret < 0) {
    fprintf(stderr, "Could not allocate raw picture buffer\n");
    exit(1);
  }

  //v4l2 init
  videoIn = (struct vdIn *) calloc(1, sizeof(struct vdIn));
  if (init_videoIn(videoIn, (char *) videodevice, width, height, format,
      grabmethod) < 0)
    exit(1);

  printf("w:%d,h:%d\n", c->width, c->height);
  time_t timep;
  timep = time(NULL);
  printf("%s\n", asctime(gmtime(&timep)));
  for (i = 0; i < 100; i++) {
    //usleep(200000);
    //从v4l2中获取数据格式为AV_PIX_FMT_YUV422P
    if (uvcGrab(videoIn) < 0) {
      fprintf(stderr, "Error grabbing\n");
      close_v4l2(videoIn);
      free(videoIn);
      exit(1);
    }
    unsigned char *yuyv = videoIn->framebuffer;
    //把数据复制到libav想要的结构中
    av_init_packet(&pkt);
    pkt.data = NULL; // packet data will be allocated by the encoder
    pkt.size = 0;
    printf("debug!!!");
    fflush(stdout);
#if 0
    /* prepare a dummy image */
    /* Y */
    for (y = 0; y < c->height; y++) {
      for (x = 0; x < c->width; x++) {
        frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
      }
    }

    /* Cb and Cr */
    for (y = 0; y < c->height/2; y++) {
      for (x = 0; x < c->width/2; x++) {
        frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
        frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
      }
    }
#else
    /* prepare  image */
    /* Y  Cb Rb */
    for (y = 0; y < c->height; y++) {
      for (x = 0; x < c->width; x++) {
        frame->data[0][y * frame->linesize[0] + x] = yuyv[y
            * frame->linesize[0] * 2 + 2 * x];
      }
    }
    /* Cb and Cr */
    for (y = 0; y < c->height; y++) {
      for (x = 0; x < c->width / 2; x++) {
        //frame->data[0][y * frame->linesize[0] + 2*x  ] = yuyv[y*frame->linesize[0]*4+4*x];
        //frame->data[0][y * frame->linesize[0] + 2*x+1] = yuyv[y*frame->linesize[0]*4+4*x+2];
        frame->data[1][y * frame->linesize[1] + x] = yuyv[y
            * frame->linesize[1] * 4 + 4 * x + 1];
        frame->data[2][y * frame->linesize[2] + x] = yuyv[y
            * frame->linesize[2] * 4 + 4 * x + 3];
      }
    }
#endif
    frame->pts = i;

    /* encode the image */
    ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
    if (ret < 0) {
      fprintf(stderr, "Error encoding frame\n");
      exit(1);
    }

    if (got_output) {
      printf("Write frame %3d (size=%5d)\n", i, pkt.size);
      fwrite(pkt.data, 1, pkt.size, f);
      av_free_packet(&pkt);
    }
    //编码
  }
  /* get the delayed frames */
  for (got_output = 1; got_output; i++) {
    fflush(stdout);

    ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
    if (ret < 0) {
      fprintf(stderr, "Error encoding frame\n");
      exit(1);
    }

    if (got_output) {
      printf("Write frame %3d (size=%5d)\n", i, pkt.size);
      fwrite(pkt.data, 1, pkt.size, f);
      av_free_packet(&pkt);
    }
  }
  timep = time(NULL);
  printf("%s\n", asctime(gmtime(&timep)));
  /* add sequence end code to have a real mpeg file */
  fwrite(endcode, 1, sizeof(endcode), f);
  fclose(f);

  avcodec_close(c);
  av_free(c);
  av_freep(&frame->data[0]);
  av_frame_free(&frame);
  printf("111\n");

  free(videoIn);
}