Recherche avancée

Sur d’autres sites (9244)

• How to use libavformat to concat 2 video files with same codec (re-muxing) ?

  5 avril 2018, par Tarhan

  I have downloaded videos from CDN in flv format (video H264 and audio AAC) and remux to them to MP4 format. But videos are limited by length. So i’ve downloaded each video in several parts : started at start point, at point 1, at point 2 (by using seek parameter in url). Each point starts little earlier than ending of previous one.
  Using av_read_frame i scanned all parts and found that intersecting packets not only have same sizes and order but also their dts/pts shifted from each other by constant value. So to concat starting video with video started at point 1 I must do following :
  1. Create output header in output file
  2. Copy all non-intersecting packets from starting video.
  3. Copy all non-intersecting packets from video started at point 1 with changed dts values by shifted it by constant

  How to do all of this using libav (not ffmpeg) ? I read How can libavformat be used without using other libav libraries. But in libav it is not working since there not avformat_alloc_output_context2 in libav. Also source avconv.c source is too complex for newbie like me to isolate parts related to stream copy operations.
  Can someone provide me example to :
  
   open input_file1 and input_file2 (only needed if procedure differs from standard in generic tutorials)
  
   open and write header for output_file with same container format and same video and audio formats
  
   write packets from input_file1 to output_file up to packet with for example pos == XXX
  
   write packets from input_file2 to output_file changing their dts (or whatever needed) by constant value
  
   write correct trailer

  Calculating of time shift in dts i made before.

• How to add an arbitrary, formatted timestamp to a video with FFMPEG ? [duplicate]

  23 avril 2018, par Neil M.

  This question already has an answer here :

  • Can ffmpeg burn in time code ?
    
    7 answers
    

  I am calling ffmpeg from a custom tool to concatenate video files while overlaying a timestamp in the output. The output video needs to have a timestamp starting at an arbitrary time. The format must be a 12-hour clock with seconds and meridiem, e.g. 10:34:59 AM or 6:13:09 PM. Here’s the full command I’m using right now :

  ffmpeg\bin\ffmpeg.exe -y -i "concat:input.mod" -ss 00:00:00 -t 00:02:17 
  
  -an -vcodec libx264 -profile:v baseline -level 13 -b:v 2000k -vf 
  
   "drawtext=fontcolor=white:fontsize=16:fontfile="/Windows/Fonts/arial.ttf":
  
  box=1:boxcolor=black@0.3:x=(w-text_w-10):y=(h-text_h-5):
  
  timecode='02\:36\:17\;00':rate=30000/1001" output.mp4

  This outputs a 2 minute, 17 second duration video beginning at the start of the input file. The output video has a timecode in the bottom-right corner beginning at the time 02:36:17 and ending at 02:38:34. What I want is exactly this, but instead of printing "02:36:17 ;00" on frame 0 and counting up from there, it should print "2:36:17 AM" on frame 0 and count up from there.

  I have tried using the localtime function to output formatted time, but the time value it uses is the time that the drawtext filter is called. It doesn’t take a parameter for an arbitrary time.

  I have also looked at the pts function, which seems to allow an arbitrary offset but only supports two formatting options, neither of which is the clock format I need.

  What is the proper way to add a timestamp with an arbitrary starting time and format using ffmpeg ?

• FFmpeg - Multiple videos with 4 areas and different play times

  25 mai 2018, par Robert Smith

  I have videos as follows

  video   time
  
  ======= =========
  
  Area 1:
  
  video1a    0-2000
  
  video1b 2500-3000
  
  video1c 3000-4000
  
  
  
  Area 2:
  
  video2a  300- 400
  
  video2b  800- 900
  
  
  
  Area 3:
  
  video3a  400- 500
  
  video3b  700- 855
  
  
  
  Area 4:
  
  video4a  400- 500
  
  video4b  800- 900

  Basically these are security camera outputs and should display in 4 areas :

  So far I have the following :

  ffmpeg
  
      -i 1.avi -i 2.avi -i 3.avi -i 4.avi
  
      -filter_complex "
  
          nullsrc=size=640x480 [base];
  
          [0:v] setpts=PTS-STARTPTS, scale=320x240 [upperleft];
  
          [1:v] setpts=PTS-STARTPTS, scale=320x240 [upperright];
  
          [2:v] setpts=PTS-STARTPTS, scale=320x240 [lowerleft];
  
          [3:v] setpts=PTS-STARTPTS, scale=320x240 [lowerright];
  
          [base][upperleft] overlay=shortest=1 [tmp1];
  
          [tmp1][upperright] overlay=shortest=1:x=320 [tmp2];
  
          [tmp2][lowerleft] overlay=shortest=1:y=240 [tmp3];
  
          [tmp3][lowerright] overlay=shortest=1:x=320:y=240
  
      "
  
      -c:v libx264 output.mp4

  But there are two things I am missing :

  • The above is only for 4 video files, I need a way to add additional files to each area (for example video1b should play at its corresponding time after video1a in the same area)
  • How do I specify the beginning/ending time as shown above for each file ?