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• Why does ffmpeg return "No such file or directory"

  4 juillet 2020, par JackNewman

  I'm trying to split a video file into 2 second increments and then merge the video back together.

  


  source_vid_path = r"C:\SplitAndMergeVids\Before\before.mp4"
ffcat_path = r'C:\SplitAndMergeVids\Chunk\video.ffcat'
chunks_path = r'C:\SplitAndMergeVids\Chunk\chunk-%03d.mp4'
segments_time = '2'
cmd_input = rf'ffmpeg -fflags +genpts -i {source_vid_path} -map 0 -c copy -f segment -segment_format mp4 -segment_time {segments_time} -segment_list {ffcat_path} -reset_timestamps 1 -v error {chunks_path}'
output = str(subprocess.run(cmd_input, shell=True, capture_output=True))
print(output)

output_path = r'C:\SplitAndMergeVids\Output\output.mp4'
second_input = rf'ffmpeg -y -v error -i {ffcat_path} -map 0 -c copy {output_path}'
output = str(subprocess.run(second_input, shell=True, capture_output=True))
print(output)


  


  First subprocess runs perfectly although the second outputs returns

  


  "Impossible to open 'chunk-000.mp4'\r\nC:\\SplitAndMergeVids\\Chunk\\video.ffcat: No such file or directory".


  


  Full output looks like

  


  CompletedProcess(args='ffmpeg -fflags +genpts -i C:\\SplitAndMergeVids\\Before\\before.mp4 -map 0 -c copy -f segment -segment_format mp4 -segment_time 2 -segment_list C:\\SplitAndMergeVids\\Chunk\\video.ffcat -reset_timestamps 1 -v error C:\\SplitAndMergeVids\\Chunk\\chunk-%03d.mp4', returncode=0, stdout=b'', stderr=b'')
CompletedProcess(args='ffmpeg -y -v error -i C:\\SplitAndMergeVids\\Chunk\\video.ffcat -map 0 -c copy C:\\SplitAndMergeVids\\Output\\output.mp4', returncode=1, stdout=b'', stderr=b"[concat @ 0000028691a6c6c0] Impossible to open 'chunk-000.mp4'\r\nC:\\SplitAndMergeVids\\Chunk\\video.ffcat: No such file or directory\r\n")


  


  When I run cmd_input and second_input manually in cmd, everything functions perfectly. I don't understand how in the first command I am making a file at "ffcat_path", then in the second command I'm using the same "ffcat_path" and it returns "No such file or directory" when it certainly does exist.

  


• FFmpeg overwrite an AVPacket

  26 janvier 2019, par Alejandro Ramírez

  Hello guys I am working with video. I wan to encrypt the I-frames of one video compressed in H.264. So I get the AVPacket from the video and compare if (AVPacket.flags & AV_PKT_FLAG_KEY) to know if the packet has an I frame, but when I try to print the AVPacket.data I don’t have any information to encrypt.
  Where can I get the information regarding to I-frame. ahead a put my code, thank you.

  #include <iostream>
  
  extern "C" {
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libswscale></libswscale>swscale.h>
  
  #include <libavutil></libavutil>avutil.h>
  
  }
  
  #define INBUF_SIZE 4096
  
  //#define AV_INPUT_BUFFER_PADDING_SIZE 32
  
  int main (int argc, char * argv[])
  
  {
  
      //av_register_all();//omit
  
      //revisar el número de argumentos en el video
  
      AVFormatContext *pFormatCtx = NULL;
  
      AVCodec *dec = NULL;
  
      AVCodecContext *pCodecCtx = NULL;
  
      AVStream *st = NULL;
  
      AVDictionary *opts = NULL;
  
      AVFrame *frame;
  
      AVPacket avpkt;
  
      uint8_t inbuf [INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
  
      FILE *f;
  
      int frame_count;
  
      int video_stream_index = -1;
  
  
  
      //av_init_packet (&amp;avpkt);
  
  
  
      memset (inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
  
      if (avformat_open_input (&amp;pFormatCtx, argv[1], NULL, NULL) != 0)
  
          return -1;
  
      if (avformat_find_stream_info (pFormatCtx, NULL) &lt; 0)
  
          return -1;
  
      //video_stream_index = av_find_best_stream (pFormatCtx,AVMEDIA_TYPE_VIDEO, -1, -1, &amp;dec,0);
  
      video_stream_index = av_find_best_stream (pFormatCtx,AVMEDIA_TYPE_VIDEO, -1, -1, &amp;dec,0);
  
      if ( video_stream_index &lt; 0)
  
          return -1;
  
      std::cout &lt;&lt; "video_stream; " &lt;&lt; video_stream_index &lt;&lt; "\n";
  
      st = pFormatCtx -> streams [video_stream_index];
  
      std::cout &lt;&lt; "number of frames " &lt;&lt; st -> nb_frames &lt;&lt; "\n";
  
      std::cout &lt;&lt; "event_flags " &lt;&lt; st -> event_flags &lt;&lt; "\n";
  
      //pCodecCtx = st -> codec;//deprecated
  
  
  
      dec = avcodec_find_decoder (st -> codecpar -> codec_id);
  
      std::cout &lt;&lt; "codec_id: " &lt;&lt; st -> codecpar -> codec_id &lt;&lt; "\n";
  
      std::cout &lt;&lt; "AV_CODEC_ID_H264: " &lt;&lt; AV_CODEC_ID_H264 &lt;&lt; "\n";
  
      if (!dec)
  
          return -1;
  
      pCodecCtx = avcodec_alloc_context3 (dec);
  
      if (!pCodecCtx)
  
          return -1;
  
      //av_dict_set (&amp;opts, "refcounted_frames", "0", 0);
  
      avcodec_parameters_to_context (pCodecCtx, st -> codecpar);
  
  
  
  
  
      std::cout &lt;&lt; "todo bien \n";    
  
      if (avcodec_open2 (pCodecCtx, dec, &amp;opts) &lt; 0)
  
          return -1;
  
      /*************hasta aqui buen codigo*********************************************/ 
  
      frame = av_frame_alloc ();
  
      if (!frame)
  
          return -1;
  
      av_init_packet (&amp;avpkt);
  
      avpkt.data = NULL;
  
      avpkt.size = 0;
  
      f = fopen (argv[1], "r");
  
      int times = 1;
  
      while (av_read_frame (pFormatCtx, &amp;avpkt) >= 0){
  
          AVPacket oripkt = avpkt;
  
          if (oripkt.stream_index == video_stream_index){
  
              if (oripkt.flags &amp; AV_PKT_FLAG_KEY){
  
                  std::cout &lt;&lt; "times: " &lt;&lt; times ++ &lt;&lt; "\n";
  
                  std::cout &lt;&lt; "avpkt.flags: " &lt;&lt; oripkt.flags &lt;&lt; "\n";
  
                  std::cout &lt;&lt; "tam avpkt.data: " &lt;&lt; sizeof(oripkt.data) &lt;&lt; "\n";
  
                  std::cout &lt;&lt; "tam avpkt.data: " &lt;&lt; oripkt.data &lt;&lt; "\n";
  
                  std::cout &lt;&lt; "oripkt.size: " &lt;&lt; oripkt.size &lt;&lt; "\n";
  
                  std::cout &lt;&lt; "oripkt.side_date_eme: " &lt;&lt; oripkt.side_data_elems &lt;&lt; "\n";
  
                  if (!oripkt.data)
  
                      std::cout &lt;&lt; "no tengo dinero \n";
  
              }
  
          }
  
      }
  
  
  
      std::cout &lt;&lt; "Fin del programa " &lt;&lt; "\n";
  
  }
  
  </iostream>

• Qt Video Recorder

  11 mai 2014, par Davlog

  I am trying to create a video recorder with Qt. What I did so far was taking a screenshot of a rectangle on the screen and save it. At the end I use ffmpeg to get a video file out of the images.

  I connected a timer’s signal timeout() to my custom slot which takes the snapshot and saves it to my tmp folder. The timer has an intervall of 1000 / 30. That should be 30 times per second. But 1000 / 30 is a little bit more than 33 milliseconds so I cannot really get 30 fps. It’s a bit more.

  I recorded a youtube video with my recorder and everything was smooth but a little bit faster / slower depending on the intervall.

  So my question basically is how do I get really 30 / 40 / 50 / ... fps ?