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• CPU spike when transitioning from a still image

  21 avril 2016, par lagnat

  After streaming a still image (with x264) for a long period of time, the transition to live video makes the CPU spike to 100% for a period of time proportionally equal to how long the still image was streaming. More specifically, transitioning after a minute will result in a CPU spike lasting about 15 seconds. Transitioning after 30 minutes will result in that spike lasting closer to 3 minutes.

  Does this symptom make any sense and is there anything I can do about it ?

• Any other better ways to extract frames from a large size video according to the timecode given ?

  6 avril 2020, par Yong En

  Given a video from youtube with at least 600 MB. The video is annotated with labels that happens in multiple timecodes. The timecodes are in millisecond (SSSS.ss). I am trying to get the frames that fall within a time period (2 timecodes). There are TWO approaches that I used with different tools, one is using openCV in python and FFmpeg in bash script :

  



  I would stick with few variables here,

  



  

  • fps = 25

  


  • timecode (after convert into second) = 333.44 to 334.00 take note that I am dealing with time period that might less than a second.

  


  



  openCV

  



  

  1. Using openCV in python, I read the video as frames into a numpy array. Using the fps from video, 25. I can estimate where do the frames that fall under this time period by diving total video duration in second with length of the numpy array.

  


  2. Problem here is I will miss out some frames here due to the video fps is not really 25 as given by the video meta info, it could be 24.xx. Any solutions ?

  


  



  ffmpeg

  



  

  1. What I did, every time I want to get the frames, I run the script.

  


  2. Problem here is I need to read the video 100 times if I have 100 time periods. Any ways to overcome this ?

  


  



  Thanks for reading it.

  


• Efficient and Perfect way to extract frames from a large size video using python or ffmpeg according the timecode given

  5 avril 2020, par Yong En

  let's say I have a video from youtube with at least 600 MB. The video is used for annotation where I have the annotated information in another text file. The annotation file has the timecode in millisecond (SSSS.ss). What I am trying to do is going into the timecode on the video and getting out the frames within the this period (TWO timecodes). There are TWO approaches that I used with different tools, one is using openCV in python and FFmpeg in bash script :

  



  I would stick with few variables here,

  



  

  • fps = 25

  


  • timecode (after convert into second) = 333.44 to 334.00 take note that I am dealing with time period that might less than a second.

  


  



  openCV

  



  

  1. Using openCV in python, I read the video into frame by frame. Ends up with a numpy array.

  


  2. Using the fps from video, eg. fps = 25. I can estimate where does the frames that fall under this time period which give me what I want.

  


  3. Problem here is I will missed out some frames here due to the video fps is not really 25 as given by the video misinformation, it could 24.xx. Any solutions ?

  


  



  ffmpeg

  



  

  1. What I did, every time I want to get the frames, I run the script.

  


  2. Problem here is I need to read the video 100 times if I have 100 time periods. Any ways to overcome this ?

  


  



  Thanks for reading it.