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• FFmpeg, how to skip late input ?

  14 novembre 2017, par user3343357

  I’m running ffmpeg to display incoming stream on a Decklink BlackMagic card with the following command line :

  ffmpeg -y -f ourFmt -probesize 32 -i - -f decklink -preset ultrafast 
  
     -pix_fmt uyvy422 -s 1920x1080 -r 30 -af volume=0.1 -max_delay 10000 
  
       DeckLink Mini Monitor

  Basically I get the video over the internet by UDP and stream it to ffmpeg stdin. Both audio and video streams have pts and dts and are fully in sync, if the connection is good there is no problems.

  However if there are issues with the connection i start getting errors, sometimes the video delay grows significantly, and audio stops working.
  The errors i get are :

  ffmpeg : [decklink @ 0x26cc600] There are not enough buffered video
  frames. Video may misbehave ! ffmpeg : [decklink @ 0x26cc600] There’s no
  buffered audio. Audio will misbehave ! ffmpeg : Last message
  repeated 4 times ffmpeg : [decklink @ 0x26cc600] There are not enough
  buffered video frames. Video may misbehave ! ffmpeg : [decklink @
  0x26cc600] There’s no buffered audio. Audio will misbehave ! ffmpeg :
  Last message repeated 3 times ffmpeg : frame= 5204 fps= 30 q=-0.0
  size=N/A time=00:02:53.76 bitrate=N/A dup=385 drop=5 speed=0.993x
  ffmpeg : [decklink @ 0x26cc600] There’s no buffered audio. Audio will
  misbehave ! ffmpeg : Last message repeated 18 times ffmpeg :
  [decklink @ 0x26cc600] There are not enough buffered video frames.
  Video may misbehave ! ffmpeg : [decklink @ 0x26cc600] There’s no
  buffered audio. Audio will misbehave !

  The problem is when the connection is back to normal, the video keeps misbehaving until I restart the stream. What I want to do is for FFmpeg to skip to the content of the last second and play synchronized video from there, drop all the late data in between, is it possible ?

• ffmpeg : check videos conformance for dash before concat

  26 janvier 2018, par Massimo Vantaggio

  I wrote a small bash file that reads a folder, generates a playlist, concatenates, adds a logo and encode the big video result for dash ready, i would like to implement it by checking before all videos conformance : if they have same fps, same resolution, same time base etc.
  Below my situation :

  #!/bin/bash
  
  # CONCAT DEMUXER
  
  #This demuxer reads a list of #files and other directives from a text file and demuxes them one after the other, as if #all their packets had been muxed together. All files must have the same streams (same #codecs, same time base, etc.) but can be wrapped in different container formats.
  
  
  
  
  
  
  
  printf "file '%s'\n" *.mp4 > playlist.txt
  
  ffmpeg -auto_convert 1 -f concat -safe 0 -i playlist.txt -c:a aac -b:a 384k -ar 48000 -ac 2 -async 1 -vsync 1 -c:v libx264 -x264opts 'keyint=50:min-keyint=50:no-scenecut' -r 25 -b:v 2400k -maxrate 2400k -bufsize 1200k -vf "scale=-1:432" -vf "movie=stable.png [watermark]; [in][watermark] overlay=main_w-overlay_w-10:10 [out]" out.mp4
  
  clear
  
  echo “VIDEO CONCAT COMPLETED”

  For example below i find this bash that calculate the total duration in second of the videos of the folder, unfortunately I’m unable to put the result into variable.. I’m newbie of bash.

  times=()
  
  for f in *.ts; do
  
      _t=$(ffmpeg -i "$f" 2>&1 | grep "Duration" | grep -o " [0-9:.]*, " | head -n1 | tr ',' ' ' | awk -F: '{ print ($1 * 3600) + ($2 * 60) + $3 }')
  
      times+=("$_t")
  
  done
  
  echo "${times[@]}" | sed 's/ /+/g' | bc

  I wish to check if the videos have the same fps, and same resolution before process, and to get into variable this duration.
  Thanks
  Massimo

• ffmpeg wav output length not correct or consistant

  3 avril 2013, par user2241026

  Trying to run a very simple command via php a exec() command. All my other commands are working fine except for a simple audio trim that I am trying to run.

  The user posts a file, and a start time (in mm:ss.xxx format). and ffmpeg is supposed to trim the file to 5 seconds after the start time. The problem is, some times it works, but other times the audio file is 6 or even 7 seconds long. I can't figure out the problem.

  Oh, I'm aware of the lack of sanitizing in the code right now.

  here is the PHP code

  //user entered number for example "01:30"
  
  //$newFilePath1 is the location of the file, no issue there
  
  $starttime = $_POST["starttime"];
  
  
  
  $makeWav1 = "ffmpeg -y -ss 00:".$starttime." -i \"$newFilePath1\" -acodec pcm_s16le -sample_rate 48000 -t 00:00:05.000 temp/audiocut1.wav";
  
  
  
  exec($makeWav1);

  Thank you for the help !!