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• Android mp4 remove rotation and rotate the video stream

  6 novembre 2018, par Mathijs Segers

  I’m having some issues trying to remove the rotation value of Android video’s.
  For some reason convertion tools in the cloud cannot seem to handle android’s rotation value correctly. f/e I have a portrait video recorded in 1080x1920 (so the file’s headers tell me it’s actually 1920x1080 with rotation : 90).

  So now I’m trying to convert these video’s to an actual 1080x1920 format when they have this rotation value but i’m kind of stuck, probably using the wrong search terms on SO and Google.

  In the hope of making things clear I’ve actually added some ffmpeg libs to android following these steps, of course with some changes to parameters. I’m building this on a Mac and this all works fine now.
  http://www.roman10.net/how-to-build-ffmpeg-with-ndk-r9/

  Now the following, I have no real clue how these libs work and how to use them or which I actually need or if I even need them at all.

  Is there anyone who can point me in the right direction of solving my issue ? Basicly the video’s are on my android filesystem and I can access them fully, before uploading I want to check the values and remove and rotate the video’s if needed.

• ffmpeg for android, out of memory on decoding rotate mp4 file with openh264

  29 octobre 2018, par da que

  Version

  • ffmpeg : 4.0.2
  • openh264 : 1.8.0

  Problem

  I try to trim a .mp4 file which metadata info contains rotate info, but I failed with the error information.

  The file stream info :

    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '1.mp4':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: isommp42
  
      creation_time   : 2018-10-09T09:40:53.000000Z
  
      location        : +39.8983+116.4145/
  
      location-eng    : +39.8983+116.4145/
  
      com.android.version: 6.0
  
    Duration: 00:00:10.56, start: 0.000000, bitrate: 8671 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 8563 kb/s, SAR 1:1 DAR 16:9, 30.01 fps, 30 tbr, 90k tbn, 180k tbc (default)
  
      Metadata:
  
        rotate          : 180
  
        creation_time   : 2018-10-09T09:40:53.000000Z
  
        handler_name    : VideoHandle
  
      Side data:
  
        displaymatrix: rotation of -180.00 degrees
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
  
      Metadata:
  
        creation_time   : 2018-10-09T09:40:53.000000Z
  
        handler_name    : SoundHandle

  ffmpeg cmd

  ffmpeg -y -i 1.mp4 -threads 4 -b:v 2000k -vcodec libopenh264 -acodec copy -ss 0 -t 3 -f mp4 -movflags faststart -strict -2 ./output.mp4

  result

  Error reinitializing filters!
  
  Failed to inject frame into filter network: Out of memory
  
  Error while processing the decoded data for stream #0:0

  Then I found this answer : ffmpeg-for-android-out-of-memory, after i added -noautorotate command to my cmd, the video is trimmed successful.

  If I use -vcodec copy instead of -vcodec libopenh264, the result also is ok, I wonder if there is a bug when libopenh264 decode with ffmpeg’s autorotate function.

  I wipe the video’s rotate info from metadata with -metadata:s:v:0 command, the newly video can be trimmed successful with the origin cmd :(

• SteamVR creating loading screen flicker when recording using FFMPEG in unity

  28 octobre 2018, par Mohamed Muzammil

  I have a heatmap plugin integrated in my Unity VR game(with SteamVR). The plugin uses eye tracking information to generate live heatmaps as the user gazes at different elements in the game. As the heatmaps are generated, the whole camera view(user’s) is overlayed with heatmaps info and written to a MP4 file using FFMPEG.

  ---

  The whole process works fine. But I have an annoying problem where during the recording the user’s camera view is not stable and keeps flickering and stops only when the recording is stopped. It interrupts the smooth flow of his game
  For now, I’ve narrowed down the code which causes the trouble,

          public void Write(byte[] data)
  
      {
  
          if (_subprocess == null) return;
  
  
  
          _stdin.Write(data);
  
          _stdin.Flush();
  
      }

  From my understanding, It is in this part of the code stdinput is invoked to write to the file system. So, I surmise that the problem must be with accessing the file system which in turn must have caused some time delay when each frame is written in the update method. Correct me if i am wrong here.
  

  The loading screen which appears during every frame write looks something like above. It interrupts the smooth flow of the game and also makes the recording useless as the user keeps focusing on the flicker rather than the actual objects of interest. I would really be grateful if someone shows light on the issue here ?