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• Getting video sped-up with FFmpeg to have the correct duration

  23 juin 2023, par Vincent Tjeng

  I've been speeding up video using ffmpeg by following these instructions. For example, to speed up the video by 4 times, I run the following command :

  



  ffmpeg -i vid.MP4 -filter:v "setpts=0.25*PTS" vid_fast.MP4


  



  While the video is sped up by the indicated amount, the duration of the video (as indicated under its properties, and also when I play the video in VLC) remains the same as the original. For example, if vid.MP4 is initially 4 minutes, then vid_fast.MP4 is also 4 minutes, rather than being 1 minute long as expected. (The additional 3 minutes just consist of the video being frozen on the last frame.)

  



  This is a bit of a hassle, since I need to delete the additional 3 minutes that I'm not interested in. Is there any way to avoid this ?

  



  Here is a bit more information on the version of ffmpeg I'm using :

  



  ffmpeg version N-69060-gcd960c8 Copyright (c) 2000-2015 the FFmpeg developers
  built on Jan 14 2015 22:13:45 with gcc 4.9.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-lib
modplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrw
b --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinge
r --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --en
able-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis
 --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-
libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enab
le-zlib
  libavutil      54. 16.100 / 54. 16.100
  libavcodec     56. 20.100 / 56. 20.100
  libavformat    56. 18.101 / 56. 18.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5.  7.101 /  5.  7.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Hyper fast Audio and Video encoder


  


• FFMPEG gem is not generate correct bitrate value for a video in rails

  23 juin 2023, par Francis

  I am using FFMPEG gem in rails, and I want to store bitrate value for a video in a table

  


  I put this code in utility library/module

  


  movie = FFMPEG::Movie.new(path)
media_detail = {duration: movie.duration, bitrate: movie.bitrate, resolution: movie.resolution}


  


  On the show page I am using number_to_human_size rails helper method for more understandable representation

  


  number_to_human_size(convert_bit_to_byte(file.bitrate))

def convert_bit_to_byte(bitrate_value)
     (bitrate_value.to_i*125)
end


  


  So I want an average bitrate value for a video in bytes for number_to_human_size method for good representation but I am not getting the average value and FFMPEG gem generates everything as expected but only in bitrate there is some problem.

  


• How to correct crop image using FFMPEG&XILINX

  17 mai 2023, par Dmytro

  I use AWS vt1 with Xilinx SDK and FFMPEG. All from the AWS box with pre-built SDK and so on.
I need to extract frames from fullHD but scale it to 480p
I stuck with it. Could someone help with the correct options ?

  


  I have this Python-based code :

  


  
        # If the video is greater than 480p, resize the frames to 480p
        if height > 480:
            command = [
                ffmpeg_path,
                '-c:v', 'mpsoc_vcu_h264',
                '-i', temp_video,
                '-filter_complex',
                'multiscale_xma=outputs=1: out_1_width=848: out_1_height=480: out_1_rate=half:[b]; [b]xvbm_convert[b1]',
                '-pix_fmt', 'yuv420p',
                '-ss', str(median_time),
                '-map', '[b1]',
                '-vframes', '1',
                '-q:v', '2',
                '-f', 'image2pipe',
                '-vcodec', 'mjpeg',
                '-y', '-'
            ]
        else:  # Preserve the original resolution
            command = [
                ffmpeg_path,
                '-c:v', 'mpsoc_vcu_h264',
                '-i', temp_video,
                '-vf', 'xvbm_convert',
                '-pix_fmt', 'yuv420p',
                '-ss', str(median_time),
                '-vframes', '1',
                '-q:v', '2',
                '-f', 'image2pipe',
                '-vcodec', 'mjpeg',
                '-y', '-'
            ]
            output = subprocess.run(command, capture_output=True)
            frame = output.stdout



  


  The second option with '-vf', 'xvbm_convert', work perfectly.
But the issue with the first.