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• A newbie Struggling with FFmpeg Video Encoding

  19 avril 2014, par iJose

  From last 1 week i have been struggling with FFmpeg video encoding.
  I am capturing the video from the device camera using UIImagePickerController.
  and the encoding it using the following function.

  After Encoding i am not able to save the video to my device camera roll.

  i used UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(filepath) it returns Zero GOD KNOWS WHY

   +(void)videoEncoder:(NSString *)filename
  
  {
  
      avcodec_register_all();
  
      int codec_id = AV_CODEC_ID_MPEG4;
  
      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 };
  
  
  
      printf("Encode video file %s\n", [filename UTF8String]);
  
  
  
      /* find the mpeg1 video encoder */
  
      codec = avcodec_find_encoder(codec_id);
  
      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 = 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 = AV_PIX_FMT_YUV420P;
  
  
  
      if(codec_id == AV_CODEC_ID_MPEG4)
  
          av_opt_set(c->priv_data, "preset", "slow", 0);
  
  
  
      /* open it */
  
      if (avcodec_open2(c, codec, NULL) < 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      f = fopen([filename UTF8String], "wb");
  
      if (!f)
  
      {
  
          fprintf(stderr, "Could not open %s\n", [filename UTF8String]);
  
          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);
  
      }
  
  
  
      /* encode 1 second of video */
  
      for(i=0;i<25;i++) {
  
          av_init_packet(&pkt);
  
          pkt.data = NULL;    // packet data will be allocated by the encoder
  
          pkt.size = 0;
  
  
  
          fflush(stdout);
  
          /* prepare a dummy image */
  
          /* Y */
  
          for(y=0;yheight;y++) {
  
              for(x=0;xwidth;x++) {
  
                  frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
  
              }
  
          }
  
  
  
          /* Cb and Cr */
  
          for(y=0;yheight/2;y++) {
  
              for(x=0;xwidth/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;
  
              }
  
          }
  
  
  
          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);
  
          }
  
      }
  
  
  
      /* 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);
  
          }
  
      }
  
  
  
      /* 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("\n");
  
  }

• blank transparent pngs behave like black canvas

  10 novembre 2015, par Anay Bose

  I am trying to create a scrolling image with imagemagick’s roll and crop functions. Its a frame-by—frame animation. The source image is a transparent png with some text written on it. The following code works and it creates the required frames, including some blank png images at first for a nice, smooth effect. These blank pngs are what creating problems when I am trying to convert my image frames into video with ffmpeg. FFMPEG is seemingly considering these blank pngs as black/dark images, so the resulting video contains a blackout for a few seconds in the beginning—which I do not want.

  I am using png codec with bgra pixel format. My ffmpeg command (shown below) creates smooth, clear animation with images that have some text on it.

  "ffmpeg -i trans/trans-%d.png -vcodec png -pix_fmt bgra overlay-0.mov";

  The blank pngs behave like black canvas, but as I try to write some text on them or surround them with a border (i.e. colorize in some way) the problem disappears—which seems very strange. I have tested all my images ; they are all transparent. For the past few hours, I have been searching for a solution, no luck so far. Please note those blank pngs are required in the beginning for a smooth effect, and I cannot omit them. I have uploaded a sample video in Youtube. Please note the black fade out.

  https://www.youtube.com/watch?v=Te3LuItxcDk&feature=youtu.be

  https://youtu.be/Te3LuItxcDk

  PHP code :

     $increment = 40;
  
     $count = 0; 
  
  
  
     for ($x=40; $x <= 640 ; $x+=$increment) 
  
     {
  
       $roll = new Imagick(DOCROOT . '/composite-0.png');
  
       $roll->rollImage($x, 0);
  
       $roll->writeImage(DOCROOT . '/roll/roll-' . $x . '.png');
  
  
  
      $crop = new Imagick(DOCROOT . '/roll/roll-' . $x . '.png');
  
      $crop->cropImage($x, 720, 0, 0);
  
      $crop->writeImage(DOCROOT . '/roll/crop-' . $x . '.png');
  
  
  
      $extent = new Imagick(DOCROOT . '/roll/crop-' . $x . '.png'); 
  
      # $extent->setImageBackgroundColor(new ImagickPixel('none'));
  
      $extent->setImageBackgroundColor(new ImagickPixel('transparent'));
  
      $extent->extentImage(640, $extent->getImageHeight(), 0, 0);
  
      $extent->setImageFormat('png'); 
  
      $extent->writeImage(DOCROOT . '/trans/trans-' . $count . '.png');
  
  
  
      $count++; 
  
     }

• Injecting Metadata into an .mp4 file

  21 août 2019, par TrueCP5

  I’m working on a library that injects metadata into a .mp4 file to allow the video to be displayed correctly as a 360 video. The input file is a standard .mp4 file in the equirectangular format. I know what metadata needs to be injected I just do not know how to inject it.

  I spent some time looking around for libraries that can do this but could only find ones for extracting metadata not injecting/embedding/writing it. The alternative I found was to use Spatial Media as a command line application to inject the metadata more easily. The problem is I know zero python whatsoever so I’m leaning towards a library/nuget package/ffmpeg script.

  Does a good nuget package/library exist that can do this or should I go for the alternative option ?

  Edit 1

  I have tried just pasting in the metadata into the correct place in the file, just in case it might work, but it didn’t.

  Edit 2

  This is the metadata injected by Google’s Spatial Media Tool which is what I am trying to achieve :

  <?xml version="1.0"?>truetrueSpherical Metadata Toolequirectangular`

  Edit 3

  I’ve also tried to do it with ffmpeg like so : ffmpeg -i input.mp4 -movflags use_metadata_tags -metadata Spherical=true -metadata Stitched=true -metadata ProjectionType=equirectangular -metadata StitchingSoftware=StreetviewJourney -codec copy output.mp4

  I think the issue with the ffmpeg method is that it does not contain the rdf:SphericalVideo part which allows the spherical video tags to be used.

  Edit 4

  When I extract the metadata using ffmpeg it contains the spherical tag in the logs but not when I output it to a ffmetadata file. This was the command I used : ffmpeg -i injected.mp4 -map_metadata -1 -f ffmetadata data.txt

  This is the output of the log :

   fps, 60 tbr, 15360 tbn, 120 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Side data:
  
        spherical: equirectangular (0.000000/0.000000/0.000000)

  Edit 5

  I also tried to get the metadata using this command : ffprobe -v error -select_streams v:0 -show_streams -of default=noprint_wrappers=1 injected.mp4

  This was the logs it outputted :

  TAG:handler_name=VideoHandler
  
  side_data_type=Spherical Mapping
  
  projection=equirectangular
  
  yaw=0
  
  pitch=0
  
  roll=0

  I then tried to use this command but it didn’t work : ffmpeg -i chapmanspeak.mp4 -movflags use_metadata_tags -metadata side_metadata_type="Spherical Mapping" -metadata projection=equirectangular -metadata yaw=0 -metadata pitch=0 -metadata roll=0 -codec copy output.mp4

  Edit 6

  I tried @VC.One’s method but I must be doing something wrong because the output file is unplayable. Here is my code :

          public static void Metadata(string inputFile, string outputFile)
  
          {
  
              byte[] metadata = HexStringToByteArray("3C 3F 78 6D 6C 20 76 65 72 73 69 6F 6E 3D 22 31 2E 30 22 3F 3E 3C 72 64 66 3A 53 70 68 65 72 69 63 61 6C 56 69 64 65 6F 0A 78 6D 6C 6E 73 3A 72 64 66 3D 22 68 74 74 70 3A 2F 2F 77 77 77 2E 77 33 2E 6F 72 67 2F 31 39 39 39 2F 30 32 2F 32 32 2D 72 64 66 2D 73 79 6E 74 61 78 2D 6E 73 23 22 0A 78 6D 6C 6E 73 3A 47 53 70 68 65 72 69 63 61 6C 3D 22 68 74 74 70 3A 2F 2F 6E 73 2E 67 6F 6F 67 6C 65 2E 63 6F 6D 2F 76 69 64 65 6F 73 2F 31 2E 30 2F 73 70 68 65 72 69 63 61 6C 2F 22 3E 3C 47 53 70 68 65 72 69 63 61 6C 3A 53 70 68 65 72 69 63 61 6C 3E 74 72 75 65 3C 2F 47 53 70 68 65 72 69 63 61 6C 3A 53 70 68 65 72 69 63 61 6C 3E 3C 47 53 70 68 65 72 69 63 61 6C 3A 53 74 69 74 63 68 65 64 3E 74 72 75 65 3C 2F 47 53 70 68 65 72 69 63 61 6C 3A 53 74 69 74 63 68 65 64 3E 3C 47 53 70 68 65 72 69 63 61 6C 3A 53 74 69 74 63 68 69 6E 67 53 6F 66 74 77 61 72 65 3E 53 70 68 65 72 69 63 61 6C 20 4D 65 74 61 64 61 74 61 20 54 6F 6F 6C 3C 2F 47 53 70 68 65 72 69 63 61 6C 3A 53 74 69 74 63 68 69 6E 67 53 6F 66 74 77 61 72 65 3E 3C 47 53 70 68 65 72 69 63 61 6C 3A 50 72 6F 6A 65 63 74 69 6F 6E 54 79 70 65 3E 65 71 75 69 72 65 63 74 61 6E 67 75 6C 61 72 3C 2F 47 53 70 68 65 72 69 63 61 6C 3A 50 72 6F 6A 65 63 74 69 6F 6E 54 79 70 65 3E 3C 2F 72 64 66 3A 53 70 68 65 72 69 63 61 6C 56 69 64 65 6F 3E");
  
              byte[] stco = HexStringToByteArray("73 74 63 6F");
  
              byte[] moov = HexStringToByteArray("6D 6F 6F 76");
  
              byte[] trak = HexStringToByteArray("74 72 61 6B");
  
  
  
              byte[] file = File.ReadAllBytes(inputFile);
  
  
  
              //find trak
  
              int trakPosition = 0;
  
              for (int a = 0; a < file.Length - trak.Length; a++)
  
              {
  
                  for (int b = 0; b < trak.Length; b++)
  
                  {
  
                      if (file[a + b] != trak[b])
  
                          break;
  
                      if (b == trak.Length - 1)
  
                          trakPosition = a;
  
                  }
  
              }
  
              if (trakPosition == 0)
  
                  throw new FileLoadException();
  
  
  
              //add metadata
  
              int trakLength = BitConverter.ToInt32(new ArraySegment<byte>(file, trakPosition - 4, 4).Reverse().ToArray(), 0);
  
              var fileList = file.ToList();
  
              fileList.InsertRange(trakPosition - 4 + trakLength, metadata);
  
              file = fileList.ToArray();
  
  
  
              ////change length - tried this as well
  
              //byte[] trakBytes = BitConverter.GetBytes(trakLength + metadata.Length).Reverse().ToArray();
  
              //for (int i = 0; i &lt; 4; i++)
  
              //    file[trakPosition - 4 + i] = trakBytes[i];
  
  
  
              //find moov
  
              int moovPosition = 0;
  
              for (int a = 0; a &lt; file.Length - moov.Length; a++)
  
              {
  
                  for (int b = 0; b &lt; moov.Length; b++)
  
                  {
  
                      if (file[a + b] != moov[b])
  
                          break;
  
                      if (b == moov.Length - 1)
  
                          moovPosition = a;
  
                  }
  
              }
  
              if (moovPosition == 0)
  
                  throw new FileLoadException();
  
  
  
              //change length
  
              int moovLength = BitConverter.ToInt32(new ArraySegment<byte>(file, moovPosition - 4, 4).Reverse().ToArray(), 0);
  
              byte[] moovBytes = BitConverter.GetBytes(moovLength + metadata.Length).Reverse().ToArray();
  
              for (int i = 0; i &lt; 4; i++)
  
                  file[moovPosition - 4 + i] = moovBytes[i];
  
  
  
              //find stco
  
              int stcoPosition = 0;
  
              for (int a = 0; a &lt; file.Length - stco.Length; a++)
  
              {
  
                  for (int b = 0; b &lt; stco.Length; b++)
  
                  {
  
                      if (file[a + b] != stco[b])
  
                          break;
  
                      if (b == stco.Length - 1)
  
                          stcoPosition = a;
  
                  }
  
              }
  
              if (stcoPosition == 0)
  
                  throw new FileLoadException();
  
  
  
              //modify entries
  
              int stcoEntries = BitConverter.ToInt32(new ArraySegment<byte>(file, stcoPosition + 8, 4).Reverse().ToArray(), 0);
  
              for (int a = stcoPosition + 12; a &lt; stcoPosition + 12 + stcoEntries * 4; a += 4)
  
              {
  
                  int entryLength = BitConverter.ToInt32(new ArraySegment<byte>(file, a, 4).Reverse().ToArray(), 0);
  
                  byte[] newEntry = BitConverter.GetBytes(entryLength + metadata.Length).Reverse().ToArray();
  
                  for (int b = 0; b &lt; 4; b++)
  
                      file[a + b] = newEntry[b];
  
              }
  
  
  
              File.WriteAllBytes(outputFile, file);
  
          }
  
  
  
          private static byte[] HexStringToByteArray(string hex)
  
          {
  
              hex = hex.Replace(" ", "");
  
              return Enumerable.Range(0, hex.Length)
  
                               .Where(x => x % 2 == 0)
  
                               .Select(x => Convert.ToByte(hex.Substring(x, 2), 16))
  
                               .ToArray();
  
          }
  
  </byte></byte></byte></byte>

  The bytes are reversed because .mp4s seem to be Little Endian. I tried to also update the length of trak but that didn’t work either.