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• Extract part of a video using ffmpeg_extract_subclip - black frames

  20 août 2020, par albert1905

  I'm trying to use : "ffmpeg_extract_subclip" for extracting part of a video.

  


  And I'm facing a few problems :

  


  1.when I'm cutting a small video (1-3seconds) I'm getting black frames, only audio is working.
2.when I'm cutting longer video, the output video is stuck 2-3 seconds before the end.

  


  This is my simple code :

  


  from moviepy.video.io.ffmpeg_tools import ffmpeg_extract_subclip

input_video_path = 'myPath/vid1.mp4'
output_video_path = 'myPath/output/vid1.mp4'
t1 = 6.5
t2 = 16    # random numbers, my last attempt..
    
ffmpeg_extract_subclip(input_video_path, t1, t2, targetname=output_video_path)


  


  I tried to look inside the code :
ffmpeg_extract_subclip Function

  


  But still couldn't understand what's wrong.. :(

  


  I'm still trying, and if anyone knows the problem or have a different approach, that will be amazing.

  


  Thanks a lot for your help !

  


• FFMPEG h.264 stream to VLC from raw YUV444 produces black screen

  30 novembre 2018, par GerbGerb

  Not sure if this fits better here or over on Super User, so please redirect if here is the wrong place.

  I am piping raw YUV444 640x480 frames to ffmpeg from inside a C++ program using stdout. ffmpeg encodes them using h.264 and streams the video via UDP to an IP of my choice.

  When I am not streaming and saving the video as -mp4 file, everything works - But when I stream over the network and try to receive in VLC, the stream is received and the playing timer under the video screen runs, but the image is black, none of the video is displayed. Also I have some crackling sounds on my audio output.

  My FFMPEG settings are as follows :

  ffmpeg -y -loglevel info -f rawvideo -r 25 -c:v rawvideo -pix_fmt yuv444p -s 640x480 -i - -c:v libx264 -preset superfast -framerate 25 -f mpegts udp://192.168.150.1:20001

  in VLC, I just use "open network stream" with udp ://@:20001. The port is open, I tested it with a simple dummy sender/receiver.
  Almost the same cli arguments for the video recording lead to a perfectly playable video when writing to a file and downloading it :

  ffmpeg -y -loglevel info -f rawvideo -r 25 -c:v rawvideo -pix_fmt yuv444p -s 640x480 -i - -c:v libx264 -preset superfast -framerate 25 video.mp4

  If I try to stream the same video using

  ffmpeg -i video.mp4 -v 0 -vcodec mpeg4 -f mpegts udp://192.168.150:20001

  the screen remains black.

  VLC debug output changes between different runs, because other modules are selected, so I assume stream type recognition goes haywire. But why ?

  What am I doing wrong ?

  Here the ffmpeg log
  and the VLC log

• Generate Black frames between concatenated videos ffmpeg

  9 février 2019, par Alex K

  I’m trying to concatenate 2 videos together using ffmpeg concat, but I want to have there be 2 seconds of black between the 2 videos.

  The problem is that whenever I’ve tried to generate a black video and concatenated it in, the properties never match my input video exactly, and so the concatenation is all broken - the audio is broken or the frames change at the wrong speed or generally concatenation fails.

  Here’s the output of ffmpeg -i my_input_video1.mp4 (and is identical for my_input_video2.mp4) :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input_vid1.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf58.3.100
  
    Duration: 00:00:03.07, start: 0.000000, bitrate: 191 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 480x270, 116 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 63 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

  How can I generate a 2 second black video with these properties so that it can be concatenated with my input videos ?