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• 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 ?

• Adding current time as timestamp in h264 raw stream with few frames

  1er avril 2020, par Michaël

  I have a program that spits out an h264 raw stream (namely, screenrecord on Android). I'm using ffmpeg to add a PTS (Presentation Time Stamp) on the frames as follows :

  



  $ my-program | ffmpeg -i - -filter:v setpts='(RTCTIME - RTCSTART) / (TB * 1000000)' out.mp4


  



  This filter computes the current time, and puts it as the PTS.

  



  The trouble is that my-program does not produce any output if there is no change in the video. Since ffmpeg seems to wait for a bunch of frames before putting them through the setpts filter, the computed PTS won't be correct. In particular, the last frame of a sequence will be timestamped when the next sequence starts.

  



  Question : Is there a way (with ffmpeg or otherwise) to add current time as PTS to h264 raw frames, where "current time" is when receiving the frame, rather than outputting it ?

  



  Note : The problem is not from buffering from the pipe.

  


• Convert AVStream PTS value to real time in seconds

  15 janvier 2015, par Kamlesh

  The below code snippet gets the PTS value of different frames from a video file

  AVStream *stream = avctx->streams[avpkt.stream_index];
  
  if ( 0 > ( err = avcodec_decode_video2 ( stream->codec, frame, &got_frame, &avpkt ) && got_frame ) )
  
  {
  
      int64_t pts = av_frame_get_best_effort_timestamp ( frame );
  
      pts = av_rescale_q ( pts,  stream->time_base, AV_TIME_BASE_Q );        
  
  } 

  The PTS value that it returns are given below.

  • 66733
  • 100100
  • 133467

  Confusion is on the time format of the above values, whether they are in milliseconds or microseconds.
  Is there any other way to get a real time PTS values of the frames, as these will be required for subtitle rendering