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• FFMPEG : Recording a video stream to disk real-time

  31 mars 2022, par Евгений Федоров

  I made a video recording with ffmpeg

  


   var inputArgs = string.Format(CultureInfo.InvariantCulture, "-framerate {0} -f rawvideo -pix_fmt {3} -video_size {1}x{2} -i -", VideoFPS, VideoXRes, VideoYRes, VideoPXLFormat);

 var outputArgs = string.Format(CultureInfo.InvariantCulture, "-vcodec mpeg4 -crf {2} -pix_fmt yuv420p -preset {3} -shortest -r {1} \"{0}\"", outputPath, VideoFPS, VideoCRFValue, CompressionRate);

 var ffmpegProcess = new Process
        {
            StartInfo =
            {
                FileName = ffmpegPath,
                Arguments = $"{inputArgs} {outputArgs}",
                UseShellExecute = false,
                CreateNoWindow = true,
                RedirectStandardInput = true
            }
        };

        ffmpegProcess .Start();
        var VideoRecordingFFmpegInput = VideoRecordingFFmpegProcces.StandardInput.BaseStream;


  


  Now I write data bytes from the image into the stream from time to time

  


  VideoRecordingFFmpegInput.Write(framesByteArray, 0, sizeOfpack);


  


  When I finished recording the frames :

  


    VideoRecordingFFmpegInput.Flush();
  VideoRecordingFFmpegInput.Close();
  ffmpegProcess.WaitForExit();


  


  Everything works fine, and it creates the file I want.

  


  When the process starts, it creates a file that has a very small size


  


  And during the recording of image bytes in the video stream - this size does not change (Probably it is written to RAM ?)

  


  But as soon as the ffmpeg process finishes - flush / close
the file size becomes normal.

  


  

  


  The problem is that if I record for several hours it can cause an OutOfMemory exception

  


  Is there any way to have the frames record and immediately increase the file size ? (Without infinitely filling RAM ?)

  


• Is it real connect subtitles when streaming video (HLS, M3U8)

  12 avril 2019, par Mikhail Petrov

  I am trying to create a stream in which the tracks from the convertible file (in my case .mkv to .m3u8) will be played through m3u8. At the moment, it turns out to switch between multiple resolutions, and even select the audio track, but does not see the subtitles at all.

  Video works, audio tracks are switched, but no subtitles are visible at all

  ffprobe source file :
  https://paste2.org/czUePDPj

  Next, perform coding and splitting into tracks :

  ffmpeg -i '/home/mishkapetran/Загрузки/Rick.mkv' \
  
  -map 0:v:0 -c:v libx264 -profile:v baseline -preset:v superfast -strict -2 -s 426x240   -f hls -hls_time 10 -hls_list_size 0 -segment_list rick240p -hls_segment_filename '/home/mishkapetran/Загрузки/test/Rick240p_%d.ts'      '/home/mishkapetran/Загрузки/test/Rick240p.m3u8' \
  
  -map 0:a:0 -c:a aac                             -f hls -hls_time 10 -hls_list_size 0 -segment_list rick_ru -hls_segment_filename '/home/mishkapetran/Загрузки/test/RickTrack_ru_%d.aac'        '/home/mishkapetran/Загрузки/test/RickTrack_ru.m3u8' \
  
  -map 0:a:1 -c:a aac                             -f hls -hls_time 10 -hls_list_size 0 -segment_list rick_en -hls_segment_filename '/home/mishkapetran/Загрузки/test/RickTrack_en_%d.aac'        '/home/mishkapetran/Загрузки/test/RickTrack_en.m3u8' \
  
  -map 0:s:0 suben.vtt                          -f hls -hls_time 10 -hls_list_size 0 -segment_list en -hls_segment_filename '/home/mishkapetran/Загрузки/test/sub_en_%d.vtt'  '/home/mishkapetran/Загрузки/test/sub_en.m3u8' \
  
  -map 0:s:1 subru.vtt                          -f hls -hls_time 10 -hls_list_size 0 -segment_list ru -hls_segment_filename '/home/mishkapetran/Загрузки/test/sub_ru_%d.vtt'  '/home/mishkapetran/Загрузки/test/sub_ru.m3u8'

  Then in the same folder I create the m3u8 master :

  #EXTM3U
  
  #EXT-X-VERSION:5
  
  #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio",NAME="Russian",LANGUAGE="ru",AUTOSELECT=YES,URI="RickTrack_ru.m3u8"
  
  #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio",NAME="English",LANGUAGE="en",AUTOSELECT=NO,URI="RickTrack_en.m3u8"
  
  
  
  #EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs",NAME="Russian",DEFAULT=YES,FORCED=NO,AUTOSELECT=YES,LANGUAGE="ru",URI="sub_ru.m3u8"
  
  #EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs",NAME="English",DEFAULT=NO,FORCED=NO,AUTOSELECT=YES,LANGUAGE="en",URI="sub_en.m3u8"
  
  
  
  #EXT-X-STREAM-INF:BANDWIDTH=928000,CODECS="avc1.42c00d,mp4a.40.2",RESOLUTION=480x270,AUDIO="audio",SUBTITLES="subs"
  
  Rick240p.m3u8

• How to mention real image instead of dummy image in ffmpeg api-example.c

  2 mars 2013, par Mohan

  I am using video_encode_example function from api-example.c of FFmpeg,
  which basically creates 25 dummy images and encodes into a one second video.
  How ever i am unable to mention real images instead of dummy ones.
  If any one know how to do this for xcode objective C, pl submit a reply.
  Below is the function

  /*
  
   * Video encoding example
  
   */
  
  static void video_encode_example(const char *filename)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int i, out_size, size, x, y, outbuf_size;
  
      FILE *f;
  
      AVFrame *picture;
  
      uint8_t *outbuf, *picture_buf;
  
  
  
      printf("Video encoding\n");
  
  
  
      /* find the mpeg1 video encoder */
  
      codec = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);
  
      if (!codec) {
  
          fprintf(stderr, "codec not found\n");
  
          exit(1);
  
      }
  
  
  
      c= avcodec_alloc_context();
  
      picture= avcodec_alloc_frame();
  
  
  
      /* put sample parameters */
  
      c->bit_rate = 400000;
  
      /* resolution must be a multiple of two */
  
      c->width = 352;
  
      c->height = 288;
  
      /* frames per second */
  
      c->time_base= (AVRational){1,25};
  
      c->gop_size = 10; /* emit one intra frame every ten frames */
  
      c->max_b_frames=1;
  
      c->pix_fmt = PIX_FMT_YUV420P;
  
  
  
      /* open it */
  
      if (avcodec_open(c, codec) < 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);
  
      }
  
  
  
      /* alloc image and output buffer */
  
      outbuf_size = 100000;
  
      outbuf = malloc(outbuf_size);
  
      size = c->width * c->height;
  
      picture_buf = malloc((size * 3) / 2); /* size for YUV 420 */
  
  
  
      picture->data[0] = picture_buf;
  
      picture->data[1] = picture->data[0] + size;
  
      picture->data[2] = picture->data[1] + size / 4;
  
      picture->linesize[0] = c->width;
  
      picture->linesize[1] = c->width / 2;
  
      picture->linesize[2] = c->width / 2;
  
  
  
      /* encode 1 second of video */
  
      for(i=0;i<25;i++) {
  
          fflush(stdout);
  
          /* prepare a dummy image */
  
          /* Y */
  
          for(y=0;yheight;y++) {
  
              for(x=0;xwidth;x++) {
  
                  picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
  
              }
  
          }
  
  
  
          /* Cb and Cr */
  
          for(y=0;yheight/2;y++) {
  
              for(x=0;xwidth/2;x++) {
  
                  picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
  
                  picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
  
              }
  
          }
  
  
  
          /* encode the image */
  
          out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);
  
          printf("encoding frame %3d (size=%5d)\n", i, out_size);
  
          fwrite(outbuf, 1, out_size, f);
  
      }
  
  
  
      /* get the delayed frames */
  
      for(; out_size; i++) {
  
          fflush(stdout);
  
  
  
          out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
  
          printf("write frame %3d (size=%5d)\n", i, out_size);
  
          fwrite(outbuf, 1, out_size, f);
  
      }
  
  
  
      /* add sequence end code to have a real mpeg file */
  
      outbuf[0] = 0x00;
  
      outbuf[1] = 0x00;
  
      outbuf[2] = 0x01;
  
      outbuf[3] = 0xb7;
  
      fwrite(outbuf, 1, 4, f);
  
      fclose(f);
  
      free(picture_buf);
  
      free(outbuf);
  
  
  
      avcodec_close(c);
  
      av_free(c);
  
      av_free(picture);
  
      printf("\n");
  
  }