Recherche avancée

Sur d’autres sites (11641)

• Estimate time and memory required when transcoding video FFMPEG [on hold]

  8 mars 2019, par Anh Vo Nguyen Nhat

  Currently, I am trying to predict beforehand the time it takes when transcoding a video (e.g. transcoding 1920x1080 H264 video to 1280x720 VP9) using FFMPEG tool.
  I have used the following features to build a simple neural network to predict the time :
   Video Resolution (Input + Output)
   Video Duration
   Video Codec (Input + Output)
   Video Bitrate
   Video Framerate
   Number of B, I, P frames

  However, the result is not really promising. I want to ask if there is any other way to estimate/predict the time it takes when transcoding a video ? Are there any other features beside the listed that affects the transcoding time ?

  Beside the transcoding time, I also need to forecast the memory required by the process. I see a linear relation between the output resolution and the consumed memory. However, when trying with different computers the consumed memory are different. For example, 128GB computer would take 57GB to transcode, but for 64GB computer, it only takes 37GB. Is there any formula to calculate the required memory from the FFMPEG transcoding algorithm ?

• Insert still frames into H.264 video stream

  7 juillet 2021, par Bassinator

  I'm building an application that receives video packets which are encoded as H.264 from Microsoft Teams - I get one packet for each frame of video. Specifications of the packet contents are given here. For every packet I receive, I write the byte contents of the data[] buffer to a file. This resulting file is a playable H.264 encoded video.

  


  I'm trying to handle the scenario of syncing the audio and video streams from a Teams meeting, and inserting a still frame PNG as a "filler" when nobody has their camera on.

  


  I used the following FFMPEG command to generate n number of seconds of H.264 video from the filler frame :

  


  ffmpeg -loop 1 -i video_filler_frame.png -framerate 30 -c:v libx264 -t 2 -vf scale=1920:1080 C:\Code\temp\out.mp4


  


  This generates an MP4 file (H.264 encoded) - as a test in my code, I tried to read the contents of that generated file as a byte array and append them to the video file.

  


  However, this doesn't appear to work. I'm guessing this is because there is some kind of header or other metadata that prevents us from doing the simple solution of just appending the bytes of the next frame.

  


  My question is, how can I achieve what I am trying to do ? I'd like to splice in n number of frames as I am writing the individual packet contents to the file. In other words, for example, consider the following sequence :

  


  

  • Write packets of video to the file

  


  • My code determines that filler frames are needed at some point in this process

    

    • Insert needed number of filler frames to the file

    


    


  


  • Continue writing packets of video as they come in

  


  


• Anomalie #3750 : Itérateur JSON, erreur de compilation lorsque la source contient &

  8 octobre 2018, par placido .

  J’avais fait le ticket au départ, notamment parce que le message de debug de compilation partait complètement en vrille, ce qui semble trahir un cas de remontée d’erreur pas bien géré.
  Pour le reste on a qu’à dire que cette page fera office de précis de documentation pour les urls de ressources JSON avec ’&’.

  Donc oui, on peut sans doute fermer.