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• avcodec/indeo3data : fix undefined left shift of negative number

  19 septembre 2015, par Ganesh Ajjanagadde

  avcodec/indeo3data : fix undefined left shift of negative number
  This fixes a whole sea of -Wshift-negative-value reported with clang 3.7+, e.g
  
  http://fate.ffmpeg.org/log.cgi?time=20150918181527&log=compile&slot=x86_64-darwin-clang-polly-vectorize-stripmine-3.7.
  
  Any half decent compiler should anyway optimize away the multiplication.
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/indeo3data.h

• Is it possible to fetch some key-frames of a video by using the HTTP Range header

  9 décembre 2020, par pvd

  I've read the SO problem , and it seems not applying to my specific case.

  


  Is it possible to fetch some key-frames of a video from web server by the HTTP Range header ? For example, for a 30 seconds duration video, we'd like to analysis the I-frame around 00:00:02, 00:00:15, 00:00:28.

  


  I need to analysis the videos from internal web server to detect if there's specific watermarks in it and some other analysis.

  


  Since the first I-frame might be invalid sometimes(Logo for example), we were planning to extract the I-frame from the 00:00:02, the middle I-frame, and the last 2nd second I-frame.

  


  For example, for a 30 seconds duration video, we'd like to analysis the I-frame around 00:00:02, 00:00:15, 00:00:28.

  


  We could make it works while download the whole video, since most of the data we downloaded from the server are not being used. I was wondering if maybe we could only use the HTTP Range header to download partial data and analysis it ?

  


• 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.