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• How to set background transparency for animation with ffmpeg

  23 octobre 2023, par Jan Turowski

  I am creating animated physics graphs with a transparent background for later use in a NLE. On my old machine at work they display and render with background transparency just fine. The exact same code however loses background transparency in the ffmpeg render on both my Linux and my Windows machine at home. The animations are displayed just fine on all machines.

  


  As I first thought it was a Linux issue, I tried to run the code on my Windows machine expecting it to work again. Unfortunately it did not.

  


  Reduced code :

  


  import numpy as np
import matplotlib.pylab as plt
from matplotlib.animation import FuncAnimation
import matplotlib.animation as animation
from matplotlib.pyplot import figure
from matplotlib import style
import locale
from matplotlib.ticker import (MultipleLocator, AutoMinorLocator)
# Set to German locale to get comma decimal separater
locale.setlocale(locale.LC_NUMERIC, "de_DE")
# Tell matplotlib to use the locale we set above
plt.rcParams['axes.formatter.use_locale'] = True

# plt.clf()
# plt.rcdefaults()

# Style und Font definieren

style.use('dark_background')

# Pfeile erstellen
def arrowed_spines(fig, ax):

    xmin, xmax = ax.get_xlim()
    ymin, ymax = ax.get_ylim()

    # removing the default axis on all sides:
    for side in ['bottom','right','top','left']:
        ax.spines[side].set_visible(False)

    # removing the axis ticks
    # plt.xticks([]) # labels
    # plt.yticks([])
    # ax.xaxis.set_ticks_position('none') # tick markers
    # ax.yaxis.set_ticks_position('none')

    # get width and height of axes object to compute
    # matching arrowhead length and width
    dps = fig.dpi_scale_trans.inverted()
    bbox = ax.get_window_extent().transformed(dps)
    width, height = bbox.width, bbox.height

    # manual arrowhead width and length
    hw = 1./20.*(ymax-ymin)
    hl = 1./20.*(xmax-xmin)
    lw = 1. # axis line width
    ohg = 0.3 # arrow overhang

    # compute matching arrowhead length and width
    yhw = hw/(ymax-ymin)*(xmax-xmin)* height/width
    yhl = hl/(xmax-xmin)*(ymax-ymin)* width/height

    # draw x and y axis
    ax.arrow(xmin, 0, xmax-xmin, 0., fc='w', ec='w', lw = lw,
             head_width=hw, head_length=hl, overhang = ohg,
             length_includes_head= True, clip_on = False)

    ax.arrow(0, ymin, 0., ymax-ymin, fc='w', ec='w', lw = lw,
             head_width=yhw, head_length=yhl, overhang = ohg,
             length_includes_head= True, clip_on = False)

# Meine easing-Funktion
def ease(n):
    if n < 0.0:
        return 0
    elif n > 1.0:
        return 1
    else:
        return 3*n**2-2*n**3

# Meine Floor/Warte Funktion
def wait(n):
    if n < 0.0:
        return 0
    else:
        return n

# Canvas erstellen
fig = plt.figure()
ax = fig.add_subplot(111)
fig.set_size_inches([8,9])

def f(x):
    return -0.05*x**2+125
xlin = np.linspace(0,60,100)


# Beschriftung und Optik

plt.xlabel(r"$x$ in $\rm{m}$", horizontalalignment='right', x=1.0)
plt.ylabel(r"$y$ in $\rm{m}$", horizontalalignment='right', y=1.0)
ax.set_xlim(0,100)
ax.set_ylim(0,139)
plt.grid(alpha=.4)
plt.xticks(np.arange(0, 100, 20))
plt.yticks(np.arange(0, 140, 20))
ax.yaxis.set_minor_locator(MultipleLocator(10))
ax.xaxis.set_minor_locator(MultipleLocator(10))
ax.tick_params(axis='x', direction = "inout", length= 10.0, which='both', width=3)
ax.tick_params(axis='y', direction = "inout", length= 10.0, which='both', width=3)


xsub = np.array([0])

# statische Linien definieren
line2, = ax.plot(xsub,f(xsub),linewidth=5,zorder=0,c = 'b')
arrowed_spines(fig, ax)
plt.tight_layout()

# Linien animieren
def animate(i):

    xsub = xlin[0:wait(i-20)]
    global line2
    line2.remove()
    line2, = ax.plot(xsub, f(xsub), linewidth=5, zorder=0,c = "b")
    plt.tight_layout()

animation = FuncAnimation(fig, animate, np.arange(0, 130, 1), interval=100)

plt.show()

# animation.save(r"YOUR\PATH\HERE\reduced_x-y.mov", codec="png",
         dpi=100, bitrate=-1,
         savefig_kwargs={'transparent': True, 'facecolor': 'none'})



  


• VLC HTTP STREAMING OVER HTTP IS STOPPING AFTER 10 SECONDS ALWAYS

  30 mai 2018, par vijayky88

  I am trying to run my Ubuntu machine as vlc server. where i run below command to stream my local video over http.vlc 1.avi

  :sout=#transcode{vcodec=theo,vb=800,acodec=vorb,ab=128,channels=2,samplerate=44100}:duplicate{dst=http{dst=:8080/test.ogg}}       :sout-all :sout-keep

  Below is vlc client commad to display the http streaming output which is stopping always after 10 sec. For subsequent attempt this is not working.("failed to find url")
  vlc http://localhost:8080/test.ogg .

  Please suggest any workaround. Also please let me knwo if i should switched to ffmpeg if this is legacy problem. please suggest the command as well.

  Note : using the latest vlc

  Thanks in advance !

• Adding outro video to multiple video files using ffmpeg

  31 août 2017, par jasan

  I can successfully merge files using the following command using ffmpeg :

  ffmpeg -f concat -i mylist.txt -c copy output.mp4

  the mylist.txt looks like this :

  file './video.mp4'
  
  file './outro.mp4'

  However what I want to do is the following :

  • I have 100 video files ( video1.mp4, video2.mp4, video3.mp4,...)

  • i have one outro file(outro.mp4)

  I want to concat outro.mp4 to the end of each of the 100 files and save each of concatenated video file with the same filename as the original videofile( i.e video1, video2....)

  I’m on a windows machine. any way I can achieve this ? code snippet would be really helpful.