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• 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.

  


• Ffmpeg sidechaincompress with different input audio lengths

  29 janvier 2023, par user19313832

  There are two input files :

  


  

  • First entry is a video with music - 6 min.

  


  • Second entry - voice - 3 min.
Here compr will contain the audio of video that is muted when start talking (second input).

  


  


  ffmpeg -y -i %pathToVideo% -i %pathToAudio% -filter_complex ^ ^"[0:a][1:a]sidechaincompress=threshold=0.015:ratio=19:level_sc=1:release=1400:attack=1[compr]^" ^ -c:v copy -map 0:v -map [compr]:a %out%

  


  Problem - sound of the video is completely turned off when the voice ends, at the 3rd minute.

  


  This works well for the first 3 minutes.
Then the sound of the video is turned off.

  


  Half of the video remains without sound.
It is necessary that the sound of the video remains, and not turned off.
It looks like it only works on audios of the same length, but here the audios are different lengths ???????????

  


  It is necessary that the sound of the video does not turn off after the 3rd minute. Because the voice file is only 3 minutes.