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• Scene change/shot detection/image extraction using ffmpeg from video

  18 February 2023, by Bharat

  I am trying to get representative frames for a video, so as to remove redundant frames which might appear in a video. This is what I use to get the frames.

  



  ./ffmpeg -i video.mp4 -vf select="eq(pict_type\,PICT_TYPE_I)" -vsync 2 -s 320x240 thumb-%02d.png

  



  I have also tried

  



  ./ffmpeg -i video.mp4 -f image2 -vf "select=gt(scene\,.4)" -vsync vfr thumb%04d.png

  



  The major issue in this is blur. If I just sample frames every 5 seconds, I don't see any blur, however using the above two commands I get a lot of blur.

  



  The video can be found here, http://www.cs.umd.edu/ bharat/video.mp4

  



  In order to sample the video every 10 seconds, I use the following:

  



  ./ffmpeg -i video.mp4 -r 1/10 filename%03d.jpg

  



  Output using normal sampling:


  



  Output using select:


  



  However, normal sampling may be bad for some videos, and may create redundant frames. Is there a way I could use some option in ffmpeg and get frames without this blur? If normal sampling can get good frames, there should be frames in the vicinity without blur. I have looked at options such as scenecut in ffmpeg however I am not familiar with using them for this application.

  


• How to fix "FFmpeg command cannot exec when multiple mp3 file to process into one" on server side

  7 February 2019, by Harshil Dholakiya

  I am using FFmpeg in my php yii2 project. FFmpeg working fine in my project but one major problem is execute FFmpeg command with multiple input file. When i try to use single file to process in ffmpeg command then it works. so, how can i fix this problem? I am using hostGator shared plan for my project. Please, help if is there any process limit or file open limit on server that i don’t know.

  I have tried using this command in php exec():

  ffmpeg -y -i /uploads/ac/10122018-09351115-a94rlvlawvikskb4vdrca.mp3 -i /uploads/ac/09012019-035928988-assknyrk8oujccwevir7.mp3 -f lavfi -i anullsrc -filter_complex "[2]atrim=duration=3[g0];[2]atrim=duration=1[g1];[2]atrim=duration=5[g2];[g0][0][g1][1][g2]concat=n=5:v=0:a=1" /uploads/jm/concat.mp3 2>&1

  Above command works local side but not working on server side.

  output on server side with error code 1:
  
  Press [q] to stop, [?] for help
  
  pthread_create failed: Resource temporarily unavailable. Try to increase `ulimit -v` or decrease `ulimit -s`.
  
  Conversion failed!

• Streaming android to windows

  13 June 2017, by iYehuda

  I’m writing an app that enables controlling android devices from windows machines.
  Major part of controlling the device is viewing it’s screen. Currently, my android app (Java code) captures the screen on a fixed rate, compresses it (JPEG) and sends it, while the windows side (C# code) receives buffers of data, each for frame, decompresses them and displays the last decompressed frame.

  Two issues came up from this solution:

  1. Compression of a single image takes 0.3 seconds, which limits me to low FPS streaming with single thread for compressing. I made a thread pool for compressing captured frames, and it damages the app performance.

  2. The compression is not optimal. The screen can be idle for a while and a continuous transmission of the same frame would be done. Usage of streaming/encoding format would be handful and can ease the network traffic.

  I searched for encoding APIs such as MediaCodec and third party libraries such as ffmpeg. All those libraries encode videos and write them to files (maybe I misunderstood them?).

  What API can I use for streaming my screen and follow these requirements:

  • Fast encoding / non blocking API
  • Outputs raw binary data for each frame. The data must be sent immediately
  • Can be embedded into my existing applicative protocol (protocol buffers based)
  • Available on C# (Windows) and Java or C++ (Android)