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• How to record an HTML animation and save it as a video, in an automated manner in the backend

  14 mai 2022, par frizurd

  I need to record a webpage and save it as a video, in an automated manner, without human interaction.

  


  I am creating a NodeJS app that generates MP4 videos on the request of the user. The user provides an MP3 file, the app generates animated waveforms for the sound file on top of an illustration.

  


  What I came up with so far is a system that opens a generated web page in the backend, plays the audio file, and shows audio visualization for the audio file on an HTML canvas element. On top of another canvas with mainly static components, such as images, that do not animate. The system records this, the output will be a video file. Finally, I will merge the video file with the sound file to create the final file for the user.

  


  I came up with 2 possible solutions but both of them have problems which I am not able to solve at the moment.

  


  ---

  


  Solution #1

  


  Use a headless browser API such as Phantomjs or Puppeteer to snatch a screenshot x time every second and pipe it to FFmpeg.

  


  The problem

  


  The problem with this is that the process is not realtime. It would work fine if it's JUST an animation but mine is dependant on the audio file. The audio file will play-on during the render which results in a glitchy 1FPS-esque video.

  


  Possible solution ?

  


  Don't play the audio file live but convert the audio file into raw data. Animate the audio visualization based on the raw data instead.
Not sure how to do this and if it's even possible.

  


  ---

  


  Solution #2

  


  Play, record, and save the animation, all in the frontend.
Could use ccapture.js to record and save a canvas.
Use a headless browser to open the page and save it to disk when it's done playing.
Doesn't sound like it's the best solution.

  


  The problem(s)

  


  I have more than 1 canvas.
It takes a while, especially when the audio file is longer than 10 minutes.
Making users wait for a long time can be a deal-breaker.

  


  Possible solution ?

  


  Merge canvases into one.

  


  No idea how to speed up the rendering time and I doubt it's possible this way.

  


• How to visualize matplotlib animation in Jupyter notebook

  23 avril 2020, par anonymous13

  I am trying to create a racing bar chart similar to the one in the link (https://towardsdatascience.com/bar-chart-race-in-python-with-matplotlib-8e687a5c8a41). 
However I am unable to see the animation in my Jupyter notebook

  



  code

  



  import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.ticker as ticker
import matplotlib.animation as animation
from IPython.display import HTML

df = pd.read_csv('https://gist.githubusercontent.com/johnburnmurdoch/4199dbe55095c3e13de8d5b2e5e5307a/raw/fa018b25c24b7b5f47fd0568937ff6c04e384786/city_populations', 
                 usecols=['name', 'group', 'year', 'value'])

current_year = 2018
dff = (df[df['year'].eq(current_year)]
       .sort_values(by='value', ascending=True)
       .head(10))

colors = dict(zip(
    ['India', 'Europe', 'Asia', 'Latin America',
     'Middle East', 'North America', 'Africa'],
    ['#adb0ff', '#ffb3ff', '#90d595', '#e48381',
     '#aafbff', '#f7bb5f', '#eafb50']
))
group_lk = df.set_index('name')['group'].to_dict()


fig, ax = plt.subplots(figsize=(15, 8))
def draw_barchart(year):
    dff = df[df['year'].eq(year)].sort_values(by='value', ascending=True).tail(10)
    ax.clear()
    ax.barh(dff['name'], dff['value'], color=[colors[group_lk[x]] for x in dff['name']])
    dx = dff['value'].max() / 200
    for i, (value, name) in enumerate(zip(dff['value'], dff['name'])):
        ax.text(value-dx, i,     name,           size=14, weight=600, ha='right', va='bottom')
        ax.text(value-dx, i-.25, group_lk[name], size=10, color='#444444', ha='right', va='baseline')
        ax.text(value+dx, i,     f'{value:,.0f}',  size=14, ha='left',  va='center')
    # ... polished styles
    ax.text(1, 0.4, year, transform=ax.transAxes, color='#777777', size=46, ha='right', weight=800)
    ax.text(0, 1.06, 'Population (thousands)', transform=ax.transAxes, size=12, color='#777777')
    ax.xaxis.set_major_formatter(ticker.StrMethodFormatter('{x:,.0f}'))
    ax.xaxis.set_ticks_position('top')
    ax.tick_params(axis='x', colors='#777777', labelsize=12)
    ax.set_yticks([])
    ax.margins(0, 0.01)
    ax.grid(which='major', axis='x', linestyle='-')
    ax.set_axisbelow(True)
    ax.text(0, 1.12, 'The most populous cities in the world from 1500 to 2018',
            transform=ax.transAxes, size=24, weight=600, ha='left')
    ax.text(1, 0, 'by @pratapvardhan; credit @jburnmurdoch', transform=ax.transAxes, ha='right',
            color='#777777', bbox=dict(facecolor='white', alpha=0.8, edgecolor='white'))
    plt.box(False)

draw_barchart(2018)

import matplotlib.animation as animation
from IPython.display import HTML
fig, ax = plt.subplots(figsize=(15, 8))
animator = animation.FuncAnimation(fig, draw_barchart, frames=range(1968, 2019))
HTML(animator.to_jshtml()) 



  



  Below is what I tried using and the errors

  



  HTML(animator.to_jshtml())  <-- Static output with buttons unable to visualize animation
plt.rcParams["animation.html"] = "jshtml"  <- no error and output
HTML(animator.to_html5_video())  <---Requested MovieWriter (ffmpeg) not available 



  



  Note I have FFmpeg installed in my system.
Can you help me with the issue

  


• Difficulties saving an animation (matplotlib)

  14 avril 2020, par Ben C.

  I have a simple animation that I want to save. I followed the example : https://matplotlib.org/examples/animation/basic_example_writer.html

  



  But I get the following error : RuntimeError : Requested MovieWriter (ffmpeg) not available

  



  I installed ffmpeg and checked via ffmpeg -version that it really is installed and the path correct.

  



  Here is my code :

  



  import numpy as np
import matplotlib.animation as animation
import matplotlib.pyplot as plt

# Set up formatting for the movie files
Writer = animation.writers['ffmpeg']
writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)

fig, ax = plt.subplots()

x = np.random.uniform(0,1)
y = np.random.uniform(0,1)


scat = ax.scatter(x,y, color= 'blue')
circle = plt.Circle((x,y), radius=0.1, color='blue', fill=False, lw=0.5)
ax.add_patch(circle)

def init():
    scat = ax.scatter(x, y, color = 'blue')
    circle = plt.Circle((x,y), radius=0.1, color='blue', fill=False, lw=0.5)

def animate(i):
    random = np.random.uniform(0,1)
    if random < 0.5:
        scat.set_color('red')
        circle.set_edgecolor('blue')
    else:
        scat.set_color('blue')
        circle.set_edgecolor('red')
    return circle, scat,


ani = animation.FuncAnimation(fig, animate, init_func=init(), interval=1000, blit=True)
ani.save('test.mp4', writer=writer)


  



  None of the proposed solution in RuntimeError : No MovieWriters available in Matplotlib animation worked for me. Any ideas ?

  



  Edit : I am using Windows (10)