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• Scene detection and concat makes my video longer (FFMPEG)

  12 avril 2019, par araujo

  I’m encoding videos by scenes. At this moment I got two solutions in order to do so. The first one is using a Python application which gives me a list of frames that represent scenes. Like this :

  285
  
  378
  
  553
  
  1145
  
  ...

  The first scene begins from the frame 1 to 285, the second from 285 to 378 and so on. So, I made a bash script which encodes all this scenes. Basically what it does is to take the current and previous frames, then convert them to time and finally run the ffmpeg command :

  begin=$(awk 'BEGIN{ print "'$previous'"/"'24'" }') 
  
  end=$(awk 'BEGIN{ print "'$current'"/"'24'" }') 
  
  time=$(awk 'BEGIN{ print "'$end'"-"'$begin'" }') 
  
  
  
  ffmpeg -i $video -r 24 -c:v libx265  -f mp4 -c:a aac -strict experimental -b:v 1.5M -ss $begin -t $time "output$count.mp4" -nostdin

  This works perfect. The second method is using ffmpeg itself. I run this commands and gives me a list of times. Like this :

  15.75
  
  23.0417
  
  56.0833
  
  71.2917
  
  ...

  Again I made a bash script that encodes all these times. In this case I don’t have to convert to times because what I got are times :

  time=$(awk 'BEGIN{ print "'$current'"-"'$previous'" }') 
  
  ffmpeg -i $video -r 24 -c:v libx265  -f mp4 -c:a aac -strict experimental -b:v 1.5M -ss $previous -t $time "output$count.mp4" -nostdin

  After all this explained it comes the problem. Once all the scenes are encoded I need to concat them and for that what I do is to create a list with the video names and then run the ffmpeg command.

  list.txt

  file 'output1.mp4'
  
  file 'output2.mp4'
  
  file 'output3.mp4'
  
  file 'output4.mp4'

  command :

  ffmpeg -f concat -i list.txt -c copy big_buck_bunny.mp4

  The problem is that the "concated" video is longer than the original by 2.11 seconds. The original one lasts 596.45 seconds and the encoded lasts 598.56. I added up every video duration and I got 598.56. So, I think the problem is in the encoding process. Both videos have the same frames number. My goal is to get metrics about the encoding process, when I run VQMT to get the PSNR and SSIM I get weird results, I think is for this problem.

  By the way, I’m using the big_buck_bunny video.

• Tools for investigating video corruption — ffmpeg / libavcodec

  11 juillet 2013, par Gopherkhan

  In my current work I'm trying to encode some images to h264 video using the FFMPEG's C library. The resulting video plays fine in VLC, but has no preview image. The video can play in VLC and Mplayer on ubuntu, but won't play on Mac or PC (in fact, it causes a "VTDecoderXPCService quit unexpectedly" error on Mac).

  If I run the resulting file through FFMPEG using the command line, the resulting file has a preview image, and plays correctly everywhere.

  Apparently the file that I get out of the program is corrupt in some weird place, but I don't have any output during my compilation or run to indicate where. I can't share my code at the moment (work code isn't open source yet :-( ), but I have tried a number of things :

  1. Writing only header and trailer data (av_write_trailer) and no frames
  2. writing frames only minus the trailer (using avcodec_encode_video2 and av_write_frame)
  3. Adjusting our time_base and frame pts values to encode only one frame per second
  4. Removing all variable frame rate code
  5. Numerous other variants that I won't bother you with here

  In creating my project, I've also followed the following tutorials :

  • Dr. Anger's FFMPEG tutorial
  • FFmpeg's Own Tutorials
  • An older tutorial from FFmpeg

  And consulted the deprecated ffmpeg functions list

  And compiled FFMPEG on ubuntu according to the official doc

  But every run of the program runs into the exact same problem.

  My question is, is there anything obvious that causes a programmatic run of FFMpeg to differ from a console run (e.g., an incomplete finalization, some threading issues, etc.) ? Like some obvious reason that a console run could repair a corrupted file ? Or is there a decent tool/method for inspecting a video file and finding the point of corruption ?

• ffmpeg "Requested output format 'decklink is not a suitable format'"

  9 février 2018, par user3104363

  I am trying to play a video using ffmpeg and decklink.
  I compiled ffmpeg from ffmpeg repo.
  I am working in ubuntu 16.04 lts.

  Here is my command :

  ./ffmpeg -err_detect ignore_err -threads 0 -re -i ./sample_1080_50i.ts -bufsize 1M -vf yadif -format_code Hi50 -f decklink -preroll 0.7 -pix_fmt uyvy422 'DeckLink Studio 4K'

  The result is :

  ffmpeg version N-89978-gcb97400 Copyright (c) 2000-2018 the FFmpeg developers
  
    built with gcc 5.1.1 (Ubuntu 5.1.0-0ubuntu11~10.04.2)
  
    configuration: --prefix=/home/sarslan/ffmpeg_build --pkg-config-flags=--static --extra-cflags='-I/home/sarslan/ffmpeg_build/include -I/home/sarslan/ffmpeg_sources/Blackmagic_DeckLink_SDK_10.9.5/Linux/include' --extra-ldflags=-L/home/sarslan/ffmpeg_build/lib --extra-libs='-lpthread -lm' --bindir=/home/sarslan/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-nonfree --enable-static --disable-shared --enable-decklink --enable-ffplay
  
    libavutil      56.  7.100 / 56.  7.100
  
    libavcodec     58. 10.100 / 58. 10.100
  
    libavformat    58.  9.100 / 58.  9.100
  
    libavdevice    58.  1.100 / 58.  1.100
  
    libavfilter     7. 11.101 /  7. 11.101
  
    libswscale      5.  0.101 /  5.  0.101
  
    libswresample   3.  0.101 /  3.  0.101
  
    libpostproc    55.  0.100 / 55.  0.100
  
  Input #0, mpegts, from './sample_1080_50i.ts':
  
    Duration: 00:05:00.08, start: 1.437333, bitrate: 4675 kb/s
  
    Program 1 
  
      Metadata:
  
        service_name    : Service01
  
        service_provider: FFmpeg
  
      Stream #0:0[0x100]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50 tbc
  
      Stream #0:1[0x101](eng): Audio: aac (LC) ([15][0][0][0] / 0x000F), 48000 Hz, stereo, fltp, 123 kb/s
  
  [NULL @ 0xb2ed180] Requested output format 'decklink' is not a suitable output format
  
  DeckLink Studio 4K: Invalid argument

  I think, this error is weird.
  I enabled decklink support with —enable-decklink, and I also check ffmpeg documentation decklink part.’decklink’ is used with -f option in every example.

  Then I check the command line, and I can’t find any error with the command.
  Do you have any idea what the problem is ?

  Thanks and best regards,