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• How can I get my saved mp4 to exactly match the output of plot.show() ?

  10 mai 2019, par Jimmy

  When I try to save the results of an animation to mp4 using ffmpeg, I am getting a jumbled mess.

  plt.show() shows exactly what I want it to show in the animation. However, when I save it using ffmpeg, the result is very different from what plt.show() returns. I have tried various arguments for fps etc. but nothing has helped.

  %matplotlib
  
  import pandas as pd
  
  import matplotlib as mpl ## uncomment this if you are running this on a Mac
  
  #mpl.use('TkAgg')         ## and want to use blit=True
  
  import matplotlib.pyplot as plt 
  
  import matplotlib.animation as animation 
  
  import numpy as np 
  
  import csv
  
  
  
  people = ('','Jim', 'Dan')
  
  plt.rcdefaults()
  
  fig, ax = plt.subplots()
  
  y_pos = np.arange(len(people))
  
  
  
  ax.set_xlim(0,10)
  
  ax.set_yticks(y_pos)
  
  ax.set_yticklabels(people)
  
  ax.invert_yaxis() 
  
  ax.set_xlabel('Skill')
  
  titleList=['Basketball','Hockey','Baseball']
  
  df=[[0,5,7],[0,4,9],[0,2,6]]
  
  def animate(i):
  
     # Example data
  
      while i<3:
  
          ax.set_yticks(y_pos)
  
          ax.set_yticklabels(people)
  
          ax.set_xlabel(titleList[i])
  
          performance=df[i]
  
  
  
          title = ax.text(0.5,0.95,str(titleList[i]), bbox={'facecolor':'w', 'alpha':0.5, 'pad':5},transform=ax.transAxes, ha="center")
  
  
  
          rects = ax.barh(y_pos, performance, align='center',
  
                  color='blue', ecolor='None')
  
          return [rect for rect in rects] + [title]
  
  
  
  
  
  ani = animation.FuncAnimation(fig,animate, frames=3, blit=True
  
                              ,interval=2000,repeat=False)
  
  
  
  plt.rcParams['animation.ffmpeg_path'] = 'C:\\ffmpeg\\bin\\ffmpeg.exe'
  
  Writer = animation.writers['ffmpeg']
  
  ani.save('test.mp4')
  
  plt.show() 

  The result is a very fast video where all the data gets written over (similar to the plt.show() results when blit=False).

• ffmpeg save video in segments, time does not match

  22 août 2022, par Yohann

  I use ffmpeg to save the rtsp live stream to the local, specify the fragment size of 2 seconds and use the current time to name the video file

  


  But the length of the returned video is not equal to 2 seconds and the interval between file names is not 2 seconds

  


  I have tried several command line arguments

  


  ffmpeg -i rtsp://192.168.18.119/live/test -f segment -strftime 1 -segment_time 2 -segment_atclocktime 1 -reset_timestamps 1 -an -vcodec copy ./%Y-%m-%d-%H.%M.%S.mp4

# execute result
2022-08-22-17.20.16.mp4  duration：00:03
2022-08-22-17.20.17.mp4  duration：00:03
2022-08-22-17.20.18.mp4  duration：00:07
2022-08-22-17.20.19.mp4  duration：00:03
2022-08-22-17.20.20.mp4  duration：00:03
# file names are not time aligned


  


  ffmpeg -i rtsp://192.168.18.119/live/test -f segment -strftime 1 -segment_time 2 -reset_timestamps 1 -an -vcodec copy ./%Y-%m-%d-%H.%M.%S.mp4

# execute result
2022-08-22-17.42.36.mp4 duration：00:03
2022-08-22-17.42.37.mp4 duration：00:03
2022-08-22-17.42.41.mD4 duration：00:03
2022-08-22-17.42.44.mp4 duration：00:03
2022-08-22-17.42.48.mp4 duration：00:03
2022-08-22-17.42.51.mp4 duration：00:03
# file names are not time aligned


  


  Expect to generate video

  


  2022-08-22-17.50.00.mp4 时长：00:02
2022-08-22-17.50.02.mp4 时长：00:02
2022-08-22-17.50.04.mD4 时长：00:02
2022-08-22-17.50.06.mp4 时长：00:02
2022-08-22-17.50.08.mp4 时长：00:02
2022-08-22-17.50.10.mp4 时长：00:02
...


  


• How do I use the ffmpeg CLI to stretch the beginning of an audio stream, using silence, to match the start of the video ?

  26 mai 2019, par enzi

  I’m encoding mpd for DashJS using ffmpeg. I’m trying to encode a video that has audio starting 26 seconds after video. When I play it use DashJS, the video refuses to show until the audio starts. What’s the best way to stretch the audio to to the beginning of the video using the ffmpeg cli using silence ?

  I’ve tried several filters but with no success.

  Here’s my command :

  "ffmpeg" "-i" "static/uploads/tmp.10370ba20dc842f7af87037c8e25e895.mkv" "-c:v" "libx264" "-x264opts" "keyint=25:min-keyint=25:no-scenecut" "-pix_fmt" "yuv420p" "-profile:v" "baseline" "-level" "3" "-coder" "1" "-g" "250" "-c:a" "libfdk_aac" "-b:a" "192k" "-ar" "44100" "-ac" "2" "-map" "0:0" "-map" "0:1" "-map" "0:2" "-map" "0:3" "-metadata" "title=Video" "-f" "dash" "-use_template" "1" "-use_timeline" "1" "-seg_duration" "5" "-init_seg_name" "$RepresentationID$-init.m4s" "-media_seg_name" "$RepresentationID$-$Time$.m4s" "-max_muxing_queue_size" "9999" "-shortest" "-avoid_negative_ts" "make_non_negative" "static/uploads/abea93fe8fe645f291beb6223398e025/index.out"

  I tried amixing evalsrc=0 with source 0:1, the stream that starts at 26 seconds but it still starts at 26 seconds.