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• Download a part of youtube video using a powershell script

  26 octobre 2024, par Nguyễn Đức Minh

  I'm writing this Powershell script :

  


  $URL = "https://www.youtube.com/watch?v=KbuwueqEJL0"
$from = 00:06:15
$to = 00:09:17

$cmdOutput = (youtube-dl --get-url $URL) 

ffmpeg -ss $from -to $to -i  -ss $from -to $to -i  output.mkv


  


  This script's purpose is to download a part of a Youtube video. I've set the variable $URL to specify the Youtube URL, while $from and $to is the start and end time of the part I want to download.

  


  $cmdOutput is used to output the stream URL. The output would have two lines : the first one is the URL for the video stream, while the second one is the audio stream URL.

  


  Currently, I don't know how to use the output as a variable and specify the line number of $cmdOutput to put it into the correct stream. I guess and would be replaced by something like $cmdOutput[line 1], and $cmdOutput[line 2], though I know that those are incorrect.

  


  I've consulted this answer, and it is handy for me to write this script. I've also read Boris Lipschitz's answer on how to do the same thing with Python, but his answer does not work.

  


  In that script, the -ss flag inputs the seeking point, and the -t <duration></duration> flag tells FFmpeg to stop encoding after the specified duration. For example, if the start time is 00:02:00 and the duration is 00:03:00, FFmpeg would download from 00:02:00 to 00:05:00, which is not the expected outcome. For some reason, his Python script skips the first 5 seconds of output, even if I replace the -t flag with -to . I've tried to edit his script, but it does not work unless you explicitly specify the time for both video and audio stream, as well as their respective stream URL.

  


• can not split video into smaller part

  13 juillet 2021, par david

  I want to split some videos into 2 sec parts and for this aim, I am trying to use the following code :

  


  ffmpeg -i invid.264 -threads 3 -vcodec copy -f segment -segment_time 2 cam_out_h264%04d.264


  


  but it cannot work properly and it produces this error in the command line :

  


  [h264 @ 000001b4caf5f580] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, h264, from 'output.264':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: h264 (High), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 30 fps, 30 tbr, 1200k tbn, 60 tbc
[segment @ 000001b4cb0e3600] Opening 'cam_out_h2640000.h264' for writing
Output #0, segment, to 'cam_out_h264%04d.h264':
  Metadata:
    encoder         : Lavf58.77.100
  Stream #0:0: Video: h264 (High), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 30 fps, 30 tbr, 30 tbn, 30 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[segment @ 000001b4cb0e3600] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
frame=  600 fps=0.0 q=-1.0 Lsize=N/A time=00:00:19.93 bitrate=N/A speed= 234x
video:19039kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


  


  what is the problem ? this video has 600 frames and it is 19.93 sec. hence, it should not have any problem for splitting into 2 sec videos.do you know what is the problem ? please help me with this issue.

  


• Detect scene change on part of the frame

  16 juin 2021, par user18130814200115

  I have a video file of an online lecture cosisting of a slideshow with audio in the background.
  
I want to save images of each slide as well as the timestamp of that slide.
I do this using the scene and metadata filters :

  


  ffmpeg -i week-01.mp4 -filter_complex "select='gt(scene,0.011)',metadata=print:file=frames/time.txt" -vsync vfr frames/img%03d.jpg


  


  This works fine exept for one thing, there is a timer onscreen on the right in the video file.
If i set the thershold small enough to pick up all the slide changes, it also picks up the timer changes.

  


  So here is my question, Can I ask ffmpeg to :

  


  

  1. analize part of the frame (only the right side till roughly 75% to the left).

  


  2. Then, on detecting a scene change in this area, save the entire frame and the timestamp.

  


  


  I though of making a script that

  


  

  1. crops the video and saves it alongside the origional

  


  2. analize the cropped video for scene changes and save the timestamps

  


  3. extract the frames from the origional video using the timestamps

  


  


  Is there a better/faster/shorter way to do this ?
Thanks in advance !