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• 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.

• 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).

• Input link in1:v0 parameters do not match the corresponding output link in0:v0 parameters (ffmpeg SAR error) [duplicate]

  4 décembre 2018, par this.lau_

  This question is an exact duplicate of :

  • FFmpeg - concat videos error, do not match the corresponding output link ?
    
    1 answer
    

  I’m getting an SAR error when using complex filters in ffmpeg and I can’t quite make sense of it. The input command is as follow (spread over multiple lines for clarity) :

  ffmpeg \
  
  -i '698cc30d2dc966eaf4dc4f6f3571df8d.mp4' \
  
  -i '76a2ffdd0d7e82d31731c6e2c0c6f4c9.mp4' \
  
  -filter_complex "\
  
      [0:v] setsar=sar=1,setpts=PTS-STARTPTS,scale=1080x1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2 [0v]; \
  
      [1:v] setsar=sar=1,setpts=PTS-STARTPTS,scale=1080x1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2 [1v]; \
  
      [0v][0:a][1v][1:a]concat=n=2:v=1:a=1[v][a]" \
  
  -map "[v]" -map "[a]" \
  
  -max_muxing_queue_size 500 \
  
  -strict -2 \
  
  out.mp4

  And I’m getting the following error :

  [Parsed_concat_8 @ 0x7fe35a70b100] Input link in1:v0 parameters (size 1080x1920, SAR 1:1) do not match the corresponding output link in0:v0 parameters (1080x1920, SAR 1216:1215)

  [Parsed_concat_8 @ 0x7fe35a70b100] Failed to configure output pad on Parsed_concat_8

  Error reinitializing filters !

  Failed to inject frame into filter network : Invalid argument

  Error while processing the decoded data for stream #1:0

  The complex filters basically scale the videos to the required dimensions (1080x1920) and add black borders below and above, or on the side to make it fit within the rectangle. It worked with some videos but not in this case for some reason and I can’t make sense of the error message.

  Any idea what it means and how to fix it ?