Newest 'ffmpeg' Questions - Stack Overflow

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• ffmpeg how to automatically detect video format

  18 mai 2019, par Sulli

  I am trying to download a bunch of videos from youtube:

  while read url channel
  do
      step=`youtube-dl -f 'bestvideo' -g $url`    
      ffmpeg -i "$step" -ss 00:00:10.00 -t 00:00:01.00 -c copy frames/"$channel".mp4;
  done < urls.csv 
  

  The problem is that the "bestvideo" format is not always the same, it can be mp4, webm, mov, and so I can't harcode the output format in the ffmpeg command.

  Can ffmpeg automatically detect the correct format for the output? Or is there a format that is always available for a youtube video?

• What does “has_b_frames” mean in FFprobe output ?

  18 mai 2019, par Sunil Kumar

  I am checking a video file using ffprobe to findout if a video file has any b_frames or not, i can see ffprobe output shows “has_b_frames=0" , “has_b_frames=1" and “has_b_frames=2" when i check for different video files.

  index=0
  codec_name=h264
  codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  profile=Main
  codec_type=video
  codec_time_base=1001/60000
  codec_tag_string=avc1
  codec_tag=0x31637661
  width=1080
  height=1920
  coded_width=1088
  coded_height=1920
  has_b_frames=1
  

  “has_b_frames=0" means there are no B frames present in video file ?

  can someone tell me what these values indicates,

• FFmpeg with libx264 skipped many frames during re-encoding

  18 mai 2019, par Igor

  I found a strange problem with FFmpeg 4.1.3 when I re-encode this video file with libx264 and I use bitrate 8000k mode.

  ffmpeg -y -i src.mp4 -c:v libx264 -preset slow -b:v 8000k dst.mp4
  

  Source video (28 seconds) shows 3 images.

  After re-encoding I see only 2 images and 3rd image is missing. I tested in latest VLC player 3.0.6, MPC-HC, Media player in Windows 10.

  If I use crf video encoding instead of bitrate everything is fine.

  Source video: https://drive.google.com/open?id=1gK06QtN8IqQNwAZeJdg7lbQgX0tkjaOn

• Record/Capture a discontinuous audio stream with ffmpeg

  18 mai 2019, par d03090

  I want to record an audio stream using ffmpeg. The problem is, that this stream is not available over the whole timespan, that I want to record.
  I have a device which takes input from a microphone, encodes it and broadcasts a rtp stream. This device can be controlled to start and stop this stream via a button (or a telnet command).

  So basicly I want to start a recording session. ffmpeg should capture this rtp stream, if the stream is available. Otherwise silence audio should be recorded and when the stream is available again, it should record this stream again and so on.

  How can I achieve this? When I start ffmpeg, it always aborts at the time the stream ends.

  For now my ffmpeg command just looks like this:

  ffmpeg -i rtp://192.168.2.255:3131 out.wav

  If this is not possible with a ffmpeg command what will be the best (or easiest) way to do this.

• ffmpeg - remove sequentially duplicate frames and write removed frames with frame number to log file

  18 mai 2019, par takla

  I want to upscale an anime with waifu2x. But it would take multiple days. So to cut down the time required, I'd like to remove some duplicated frames first.

  I need some help in figuring out how to remove duplicated frames from a video but write these removed frames to a log file, with the accurate frame number, e.g. lets say 04453, 04454, 04455 were duplicates, I want these numbers to be written to a log file. I know the answer in this thread comes pretty close to what I want to achieve https://stackoverflow.com/a/37089629 but I have no idea how to process from there.