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• Closed Captioned TS to Open Captioned MP4 (w/Accurate Positioning)

  19 décembre 2019, par Cody Greene

  I am attempting to convert closed captioned MPEG TS files to open captioned MP4s using ffmpeg.

  I am having trouble retaining the positioning of the captions.

  The closest I’ve gotten is with this simple script :

  ffmpeg -f lavfi -i movie=input.ts[out+subcc] -map 0:1 output.ass
  
  ffmpeg -i input.ts -vf "subtitles=output.ass" -c:v libx264 -pix_fmt yuv420p -b:v 8000k -c:a aac -b:a 192k target.mp4

  The result of this is the open captions are shifted FAR left and the bounding box draws black over the empty spaces left of wherever text is centered (ssa adds "/h", easily removed with sed, but then it’s left-aligned captions only)

  However, the vertical position, overall size, etc. all look great.

  Most subtitle formats force everything to the bottom center, but I’m trying to mimic the look of an open caption on the mp4 output.

  I’ve tried several formats with ccextractor and ffmpeg, but no luck. Any ideas what I’m doing wrong ?

• Record multiple RTSP streams into a single file

  18 décembre 2019, par John

  I need to record 4 RTSP streams into a single file.

  Streams must be placed into the video in this way :

   ---------- ---------- 
  
  |          |          |
  
  | STREAM 1 | STREAM 2 |
  
  |          |          |
  
  |----------|----------|
  
  |          |          |
  
  | STREAM 3 | STREAM 4 |
  
  |          |          |
  
   ---------- ----------

  I need to synchronize these live streams with about 1 second accuracy. This is challenging because streams have variable framerate (FPS).

  I have tried ffmpeg but streams are not synchronized.
  Here is the code :

  ffmpeg \
  
    -i "rtsp://IP-ADDRESS/cam/realmonitor?channel=1&subtype=00" \
  
    -i "rtsp://IP-ADDRESS/live?real_stream" \
  
    -i "rtsp://IP-ADDRESS/live?real_stream" \
  
    -i "rtsp://IP-ADDRESS/live?real_stream" \
  
    -filter_complex " \
  
      nullsrc=size=1920x1080 [base]; \
  
      [0:v] scale=960x540 [video0]; \
  
      [1:v] scale=960x540 [video1]; \
  
      [2:v] scale=960x540 [video2]; \
  
      [3:v] scale=960x540 [video3]; \
  
      [base][video0] overlay=shortest=1:x=0:y=0 [tmp1]; \
  
      [tmp1][video1] overlay=shortest=0:x=960:y=0 [tmp2]; \
  
      [tmp2][video2] overlay=shortest=0:x=0:y=540 [tmp3]; \
  
      [tmp3][video3] overlay=shortest=0:x=960:y=540 [v]; \
  
      [0:a]amix=inputs=1[a]" \
  
    -map "[v]" -map "[a]" -c:v h264 videos/test-combine-cams.mp4

  Is there a way to combine and synchronize streams in ffmpeg or using other utilities like : vlc, openRTSP, OpenCV ?

• ffmpeg blackdetect, start_black value to mkv chapter ?

  2 décembre 2019, par stackoverflowknitter

  I’m trying to do automatic detect chapter with blackdetect with ffmpeg.

  When I use blackdetect I get result but what is the result ? Its not frames ? Also. Is it possible to do a script/bat-file (for windows 10, powershell or cmd) to convert the result to a "mkv xml-file" so It can be imported with mkvtoolnix ?

  ffmpeg -i "movie.mp4" -vf blackdetect=d=0.232:pix_th=0.1 -an -f null - 2>&1 | findstr black_duration > output.txt

  result :

   black_start:2457.04 black_end:2460.04 black_duration:3
  
   black_start:3149.46 black_end:3152.88 black_duration:3.41667
  
   black_start:3265.62 black_end:3268.83 black_duration:3.20833
  
   black_start:3381.42 black_end:3381.92 black_duration:0.5
  
   black_start:3386.88 black_end:3387.38 black_duration:0.5
  
   black_start:3390.83 black_end:3391.33 black_duration:0.5
  
   black_start:3824.29 black_end:3824.58 black_duration:0.291667
  
   black_start:3832.71 black_end:3833.08 black_duration:0.375
  
   black_start:3916.29 black_end:3920.29 black_duration:4