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• Matching a specific media format with ffmpeg/avconv

  5 mai 2020, par Markus A.

  I need to encode a video from static images in such a way that it format-matches another one so I can splice the video streams together.

  



  Here is the mediainfo of the file I'm trying to match :

  



  Video
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Baseline@L3.1
Format settings, CABAC                   : No
Format settings, ReFrames                : 1 frame
Codec ID                                 : 7
Duration                                 : 2mn 46s
Bit rate                                 : 1 614 Kbps
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Standard                                 : NTSC
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Stream size                              : 32.0 MiB (87%)
Color primaries                          : BT.601 PAL
Transfer characteristics                 : BT.601
Matrix coefficients                      : BT.601


  



  So far, what I have been able to come up with is the following :

  



  avconv -f image2 -framerate 1.2 -i loop_%d.tif -c:v libx264 -preset veryslow -profile:v baseline -level:v 31 -b:v 1614K -refs 1 loop.flv


  



  This gets me to :

  



  Video
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Baseline@L3.1
Format settings, CABAC                   : No
Format settings, ReFrames                : 1 frame
Codec ID                                 : 7
Duration                                 : 2s 917ms
Bit rate                                 : 1 614 Kbps
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 1.200 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 1.459
Stream size                              : 575 KiB
Writing library                          : x264 core 142 r2431 a5831aa
Encoding settings                        : cabac=0 / ref=1 / deblock=1:0:0 / analyse=0x1:0x131 / me=umh / subme=10 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=0 / me_range=24 / chroma_me=1 / trellis=2 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=6 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=0 / keyint=250 / keyint_min=1 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=abr / mbtree=1 / bitrate=1614 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00


  



  Which, unfortunately, still isn't good enough as VLC Media Player crashes hard (just closes), logging main error: Failed to compensate for the format changes, removing all filters; main error: Failed to create video converter as soon as the stream splice occurs. I tried splicing another stream in that does have the exact same encoding, and it works fine. I'm also making sure to only splice on key-frames and I am including the NALU containing the AVCDecoderConfigRecord, so I'm pretty sure I'm not doing anything else wrong, especially since a couple other programs are fine with the splice. It's just VLC that expects an even closer match.

  



  Here are things I've tried :

  



  

  • Adding -vsync 2 to get variable frame rate mode. Doesn't change anything.

  


  • Adding -color_primaries bt470bg -color_trc gamma28 -colorspace bt470bg to try to get BT.601 PAL settings (several websites mentioned this). Doesn't change anything.

  


  • Adding -s ntsc to set the standard to NTSC. This also changes the resolution to 720x480 (not OK), and specifying -s 1280x720 in addition gets rid of the NTSC tag again.

  


  



  If anyone knows what flags I need to supply to get closer, that would be super-helpful ! The stream I'm trying to match is encoded on an Android device (it's a live-stream), so I'm assuming it is built using the standard Android MediaCoder framework, in case that helps.

  


• Ffmpeg - Generate VTT File From Sprite, Using Spatial Media Fragment

  20 octobre 2019, par David

  Hi I am looking to create a .VTT file from a sprite that i have generated using Ffmpeg.

  Ffmpeg command :

   $"-i {inputMediaFile} -vf \"select = not(mod(n\\, 30)),scale = 120:80,tile = 7x7\" -an -vsync 0 {outputMediaFile}"

  This selects every 30th frame, and then scales it to 120x80 pixels and creates 8x8 tiles in the output image.

  I would like to make a .VTT from the generated image in C#, so i know the height and width of my individual images in the sprite (120x80) and there is 64 images in total in the output image.

  From this i need to produce a VTT like this :

  WEBVTT
  
  
  
  1
  
  00:00:00.000 --> 00:00:01.000
  
  test-00001.jpg#xywh=0,0,120,80
  
  
  
  2
  
  00:00:01.000 --> 00:00:02.000
  
  test-00001.jpg#xywh=120,0,120,80
  
  
  
  3
  
  00:00:02.000 --> 00:00:03.000
  
  test-00001.jpg#xywh=240,0,120,80
  
  
  
  4
  
  00:00:03.000 --> 00:00:04.000
  
  test-00001.jpg#xywh=360,0,120,80
  
  
  
  5
  
  00:00:04.000 --> 00:00:05.000
  
  test-00001.jpg#xywh=480,0,120,80
  
  
  
  6
  
  00:00:05.000 --> 00:00:06.000
  
  test-00001.jpg#xywh=600,0,120,80
  
  
  
  7
  
  00:00:06.000 --> 00:00:07.000
  
  test-00001.jpg#xywh=720,0,120,80
  
  
  
  8
  
  00:00:07.000 --> 00:00:08.000
  
  test-00001.jpg#xywh=840,0,120,80
  
  
  
  9
  
  00:00:08.000 --> 00:00:09.000
  
  test-00001.jpg#xywh=0,80,120,80

  There is also situations when there is n amount of sprite files.

  Im hoping there may be a library out there that can handle this, or even better if i can keep it contained within Ffmpeg - based on Ffmpeg docs i dont think this is possible though.

  Thanks in advance if anyone as any ideas, its doable as ive seen Nodejs and Ruby examples.

• how to output a media stream using ffmpeg ?

  26 juin 2017, par Sanduni Wickramasinghe

  I am reading a mpeg4 video stream using ffmpeg. I use some of its properties and do some processes using those properties. What I want is to play the opened video using a player like vlc. And then consequently I need to play the output video after processing in order to check whether there is a latency. Is it possible to give the video to a port. So that I can get the video as a input to the vlc player from the specific port.

  This is my code up to now. I use MV_generation method to extract features from it and to do a comparison from it.

  static int MV_generation(const AVPacket *pkt)
  
  {
  
      std::vector<unsigned long="long"> vl = File_read();
  
      std::hash<string> hash1;
  
      std::ios_base::app);
  
      double x_src_val = 0;
  
      double y_src_val = 0;
  
      double x_dst_val = 0;
  
      double y_dst_val = 0;
  
  
  
      int ret = avcodec_send_packet(video_dec_ctx, pkt);
  
      if (ret &lt; 0) {
  
          //fprintf(stderr, "Error while sending a packet to the decoder: %s\n", av_err2str(ret));
  
          return ret;
  
      }
  
      video_frame_count++;
  
      while (ret >= 0){
  
  
  
          ret = avcodec_receive_frame(video_dec_ctx, frame);
  
          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
  
              break;
  
          }
  
          else if (ret &lt; 0) {
  
              return ret;
  
          }
  
          if (ret >= 0) {
  
              AVFrameSideData *sd;
  
              sd = av_frame_get_side_data(frame, AV_FRAME_DATA_MOTION_VECTORS);
  
  
  
              if (sd) {
  
  
  
                  const AVMotionVector *mvs = (const AVMotionVector *)sd->data;
  
  
  
                  int size_sd = sd->size;
  
                  //outData &lt;&lt; size_sd &lt;&lt; endl;
  
  
  
                  string str = "", str1, str2, str3, str4;
  
                  for (int i = 0; i &lt; size_sd / sizeof(*mvs); i++) {
  
                      const AVMotionVector *mv = &amp;mvs[i];
  
  
  
                      int x_src = mv->src_x;
  
                      int y_src = mv->src_y;
  
                      int x_dst = mv->dst_x;
  
                      int y_dst = mv->dst_y;
  
  
  
  
  
                      if (x_src != x_dst || y_src != y_dst || x_src > 100 || y_src > 100 || x_dst > 100 || y_dst > 100){
  
                          str1 = to_string(x_src);
  
                          str2 = to_string(y_src);
  
                          str3 = to_string(x_dst);
  
                          str4 = to_string(y_dst);
  
  
  
                          str = str.append(str1).append(str2).append(str3).append(str4);
  
                      }
  
                  }
  
  
  
                  for (unsigned long long y : vl)
  
                  {
  
                      // Check if any of the numbers are equal to x
  
                      if (hash1(str) == y)
  
                      {
  
                          cout &lt;&lt; "matched frame_no : " &lt;&lt; video_frame_count &lt;&lt; endl;
  
                      }
  
                  }
  
              }
  
              av_frame_unref(frame);
  
          }
  
      }
  
      outData.close();
  
      return 0;
  
  }
  
  </string></unsigned>