Recherche avancée

Sur d’autres sites (4144)

• C++ ffmpeg API created video does not open in some players

  18 novembre 2017, par ar2015

  After my previous question, I found codes from here to create videos in C++ using avcodec of ffmpeg libraries.

  I have modified this code to comply with C++. Everything is fine and it creates mp4 videos. Except for the output video opens with some video managers and does not open with some others.

  E.g. I can open it on Linux by totem (the slider does not allow back and forth anyway). But VLC (on the same Linux machine) does not open this file. Probably, there will be similar problem in windows.

  Is there any missing process for this code causing this problem ?

  #include 
  
  #include 
  
  #include 
  
  #include <string>
  
  #include <iostream>
  
  
  
  extern "C" {
  
      #include <libavcodec></libavcodec>avcodec.h>
  
      #include <libavutil></libavutil>opt.h>
  
      #include <libavutil></libavutil>imgutils.h>
  
  }
  
  
  
  static void encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt,
  
                     FILE *outfile)
  
  {
  
      int ret;
  
  
  
      /* send the frame to the encoder */
  
      if (frame)
  
          std::cout&lt;&lt;"Send frame "&lt;&lt;(frame->pts)&lt;= 0) {
  
          ret = avcodec_receive_packet(enc_ctx, pkt);
  
          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
  
              return;
  
          else if (ret &lt; 0) {
  
              fprintf(stderr, "Error during encoding\n");
  
              exit(1);
  
          }
  
  
  
          std::cout&lt;&lt;"Write packet "&lt;&lt;(pkt->pts)&lt;&lt;" (size="&lt;&lt;(pkt->size)&lt;&lt;")"&lt;/ printf("Write packet %3" PRId64" (size=%5d)\n", pkt->pts, pkt->size);
  
          fwrite(pkt->data, 1, pkt->size, outfile);
  
          av_packet_unref(pkt);
  
      }
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
      const char *filename;
  
      const AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int i, ret, x, y;
  
      FILE *f;
  
      AVFrame *frame;
  
      AVPacket *pkt;
  
      uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  
  
      if (argc &lt; 2) {
  
          fprintf(stderr, "Usage: %s <output file="file">\n", argv[0]);
  
          exit(0);
  
      }
  
      filename = argv[1];
  
      std::string codec_name = "mpeg4";
  
  
  
      avcodec_register_all();
  
  
  
      /* find the mpeg1video encoder */
  
      codec = avcodec_find_encoder_by_name(codec_name.c_str());
  
      if (!codec) {
  
          fprintf(stderr, "Codec '%s' not found\n", codec_name.c_str());
  
          exit(1);
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate video codec context\n");
  
          exit(1);
  
      }
  
  
  
      pkt = av_packet_alloc();
  
      if (!pkt)
  
          exit(1);
  
  
  
      /* put sample parameters */
  
      // c->bit_rate = 400000;
  
      c->bit_rate = 4000000;
  
      /* resolution must be a multiple of two */
  
      // c->width = 352;
  
      // c->height = 288;
  
      c->width = 640;
  
      c->height = 480;
  
      /* frames per second */
  
      c->time_base = (AVRational){1, 25};
  
      c->framerate = (AVRational){25, 1};
  
  
  
      /* emit one intra frame every ten frames
  
       * check frame pict_type before passing frame
  
       * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
  
       * then gop_size is ignored and the output of encoder
  
       * will always be I frame irrespective to gop_size
  
       */
  
      c->gop_size = 10;
  
      c->max_b_frames = 1;
  
      c->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      if (codec->id == AV_CODEC_ID_H264)
  
          av_opt_set(c->priv_data, "preset", "slow", 0);
  
  
  
      /* open it */
  
      ret = avcodec_open2(c, codec, NULL);
  
      if (ret &lt; 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          // fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
  
          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;
  
  
  
      ret = av_frame_get_buffer(frame, 32);
  
      if (ret &lt; 0) {
  
          fprintf(stderr, "Could not allocate the video frame data\n");
  
          exit(1);
  
      }
  
  
  
      /* encode 10 second of video */
  
      for (i = 0; i &lt; 250; i++) {
  
          fflush(stdout);
  
  
  
          /* make sure the frame data is writable */
  
          ret = av_frame_make_writable(frame);
  
          if (ret &lt; 0)
  
              exit(1);
  
  
  
          /* prepare a dummy image */
  
          /* Y */
  
          for (y = 0; y &lt; c->height; y++) {
  
              for (x = 0; x &lt; c->width; x++) {
  
                  frame->data[0][y * frame->linesize[0] + x] = uint8_t(x + y + i * 3);
  
              }
  
          }
  
  
  
          /* Cb and Cr */
  
          for (y = 0; y &lt; c->height/2; y++) {
  
              for (x = 0; x &lt; c->width/2; x++) {
  
                  frame->data[1][y * frame->linesize[1] + x] = uint8_t(128 + y + i * 2);
  
                  frame->data[2][y * frame->linesize[2] + x] = uint8_t(64 + x + i * 5);
  
              }
  
          }
  
  
  
          frame->pts = i;
  
  
  
          /* encode the image */
  
          encode(c, frame, pkt, f);
  
      }
  
  
  
      /* flush the encoder */
  
      encode(c, NULL, pkt, f);
  
  
  
      /* add sequence end code to have a real MPEG file */
  
      fwrite(endcode, 1, sizeof(endcode), f);
  
      fclose(f);
  
  
  
      avcodec_free_context(&amp;c);
  
      av_frame_free(&amp;frame);
  
      av_packet_free(&amp;pkt);
  
  
  
      return 0;
  
  }
  
  </output></iostream></string>

  build :

  g++ -I ./FFmpeg/ video.cpp -L ./fflibs -lavdevice -lavfilter -lavformat -lavcodec -lrt -ldl -lXfixes -lXext -lX11 -lasound -lSDL -lz -lrt -lswresample -lswscale -lavutil -lm -llzma -lbz2 -lswresample -lpthread

  run

  ./a.out myvideo.mp4

  This video will be fine if converted in bash via

  ffmpeg -i myvideo.mp4 out1.mp4

  But I look for a method to fix it from the code.

  Generated video played on totem (Ubuntu) :

  

  Video after conversion :

  

• Can not open a video file in OpenCV

  31 octobre 2017, par mans

  I have a video file that encoded in h264 and save in mkv format (*.mkv).
  I can pen file in VLC and play it, but I want to open it in OpenCV and extract each frame of the video.

  I have this code :

  std::string fileName = "D:/Temp/video.mkv";
  
  
  
  cv::VideoCapture capture(fileName);
  
  capture.set(CV_CAP_PROP_FOURCC, CV_FOURCC('H', '2', '6', '4'));
  
  if (!capture.isOpened())
  
  {
  
      //error!
  
      std::cout << "Can not load video";
  
  }
  
  else
  
  {
  
      double prevtimestamp = 0;
  
      cv::Mat frame;
  
  
  
      while (1)
  
      {
  
          capture.grab();
  
          double timestamp = capture.get(CV_CAP_PROP_POS_MSEC);
  
  
  
      }
  
  }

  when I run this code, I am getting message that the file can not be open.

  My questions :

  1. Is there anything wrong with this code ?
  2. Do I need FFMPEG on the path so OpenCV can open h264 videos ?
  3. How can I get more information why OpenCV can not open the file ?

• FFMPEG Open several video files at the same time ? C++ [on hold]

  8 octobre 2017, par LemanRass

  I wrote a C++ plugin for playing videos using FFmpeg libraries. All works perfectly when playing a single video, but when I try to play at least 2 videos at the same time I have these errors :

  #01 pc 0000714d  /data/app/com.ffmpeg.sdk.videoplugin-
  
  1/lib/arm/libAndroidVideoPlugin.so (_ZN12FFmpegReader13ReadNextFrameEPvPc+404)
  
  #02 pc 00005a9f  /data/app/com.ffmpeg.sdk.videoplugin-
  
  1/lib/arm/libAndroidVideoPlugin.so (_ZN9Videofile17UpdateFramesCacheEv+118)
  
  #03 pc 000057d1  /data/app/com.ffmpeg.sdk.videoplugin-
  
  1/lib/arm/libAndroidVideoPlugin.so (_firstUpdateThread+80)

  It seems that when I open the second video it, replaces the first one.
  I came up with this idea when I opened 2 videos one by one (without any errors) then I started to play only the second one and as a result I didn’t get any errors. But when I tried to read frames from the first video, my app crashed with the error above.

  A bit about plugin`s structure :

  1. I created a class called FFmpegReader where methods work
     directly with ffmpeg (Opening file, ReadFrames and returning them as void*,
     Seek and Close).

  2. Then I created one more class which creates a FFmpegReader instance using
     the "new" operator inside its constructor, descriptor (unique id of the opened
     file), queue of cached frames (up to 100 at the same time) and
     methods to operate with FFmpegReader and framesCache.

  3. I created a main file where I created a vector of objects of class from
     the second point I described above. Also I declared 4 threads for each
     opened video file (4 opened videos is the max number of allowed opened
     videos at the same time). They call the method to update a cache of frames in
     its own video file using the video file descriptor. Finally I declared methods
     which will be called from the main app which is using this plugin to retrieve
     cached frames from cache.

  As you can see, I did everything to let it works separately with each new opened video. It seems the problem is inside of FFmpeg. There might be some restrictions I’m not aware of.

  ================UPDATE=================

  Sources of Main: https://pastebin.com/DfGH0BRZ
  
  Sources of Videofile class: https://pastebin.com/WjdS532B
  
  Sources of FFmpegReader class: https://pastebin.com/aPHpBvBv

  Hope it’s gonna help...