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• Auto aspect on stream with ffmpeg

  6 mars 2018, par Felix Bäder

  I currently try to get an image each second from a udp stream with the following configuration :

  ffmpeg -i udp://localhost:1234 -vf "scale=iw*sar:ih , pad=max(iw\,ih*(16/9)):ow/(16/9):(ow-iw)/2:(oh-ih)/2" -aspect 16:9  -update 1 img.jpg
  
  
  
    Metadata:
  
      encoder         : Lavf57.83.100
  
      Stream #0:0: Video: mjpeg, yuvj420p(pc), 1024x576 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
  
      Metadata:
  
        encoder         : Lavc57.107.100 mjpeg
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1

  If the first frame of stream is 4:3 black borders are added to the output image. If the aspect is changed in stream from 4:3 to 16:9 the output image still contains the black broder and the aspect of the image between the borders is 4:3.

  If I restart ffmpeg while the aspect is 16:9 the borders are removed from the output and the output image looks fine.

  In the console I get the following log on the aspect change of stream :

  [swscaler @ 0x7fc6b1035600] deprecated pixel format used, make sure you did set range correctly

  Is there any option to fix this issue.

• How to sync two videos of different length

  26 août 2020, par Huhngut

  I got two video files. The first one has good resolution but the wrong language and the second one has bad resolution but the wished language. Both of the files got a few seconds of black screen at the beginning but these seconds are different. I got a lot of these files and the intro seems to be always of a different length so I can't say always remove 2 seconds of audio and 3 seconds of video and then merge them.

  


  So I am wondering if there's some tool out there which s able to sync these files automatically.

  


  But it won't be enough to simply search for two identical images and calculate the time distance because the resolution is different (might its possible to scale the better one down for comparison) but even in this case, the program has to evaluate if the image has enough detail for comparison so it won't compare 2 black images. It would be good if the program scales the images to 50x50 to save time while comparing

  


  Does someone know any tool or has suggestions might even some python/java code for developing one. Any search suggestions or name ideas

  


• ffmpeg : overlay video on top of a cropped video, map the overlay audio, cut the base video to the overlays length

  14 mars 2023, par roku

  I'm trying to overlay a video on top of a base video which is cropped to a shorts video format (standing phone). The overlayed video should be centered on top of the base layer. The base video's length should be reduced to the overlay's length. And I want to save only the overlay's audio.

  


  I've tried a bunch of stuff without much success. The current state of my ffmpeg command is this :

  


  ffmpeg -i overlay.mp4 -ss 00:00:00 -to <insert base="base"> -i base.mp4 -map 1:v:0 -map 1:a -vf "crop=ih*(9/16):ih" -crf 21 output.mp4&#xA;</insert>

  


  But this only gives me the cropped version of the base video. So my questions are :

  


  

  1. How can I figure out the base video's length ?

  


  2. How can I actually overlay (not map) other video on top of the base video ?

  


  3. How can I map the overlay's audio ? Since -map 1:a the base's audio and -map 0:a says : "Stream map '0:a' matches no streams. To ignore this, add a trailing ' ?' to the map."

  


  


  Any help is appreciated.