Question

我试图绘制一个动画正弦信号，好像它正穿过图形窗口一样。因此，我希望3秒正弦信号通过动画中的2秒窗口需要5秒。

但是，实时查看弹出图，使用下面的代码（改编自这个出色的教程：https://jakevdp.github.io/blog/2012/08/18/matplotlib-animation-tutorial/），机器上的时钟时间要花两倍的时间。

虽然在指定的帧频下录制的视频还是可以的。

我似乎看不出我在逻辑上做错了什么。这仅仅是性能问题吗？如果是这样，我应该如何在有约束的情况下优化代码，例如，如果可能的话，我希望不必降低采样率？目的是为绘制来自网络的实时数据做准备。

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
import sys

# Signal comes in from right to left.

SR = 44100  # sampling rate in Hz
DurSec = 3  # Signal duration in seconds
Freq = 440  # frequency in Hz
Amp = 1.0   # amplitude
WindowDurSec = 2  # figure window size in seconds

FPS = 30    # frame per second
msPerSec = 1000
frameDurMs = int(np.floor(1 / FPS * msPerSec))  # animation frame duration
passThruSec = WindowDurSec + DurSec  # Playback stops at DurSec, but graph moves on until leaving window.
passThruFrames = int(round(FPS * passThruSec))  # number of frames of the entire animation.
sampPerFrame = int(frameDurMs/1000*SR)  # frame size in samples
sampPerWindow = int(SR*WindowDurSec)  # window size in samples

x = np.linspace(0, DurSec, int(SR*DurSec))
y = Amp * np.sin(2 * np.pi * Freq * x)  # effective signal

# Add head and tail = 2 * windowSize
pad = np.zeros((sampPerWindow,), dtype=float)
Y = np.concatenate((pad, y, pad))


# Set up the figure
fig = plt.figure()
ax = plt.axes(xlim=(0, WindowDurSec), ylim=(-2*Amp, 2*Amp))
line, = ax.plot([], [], lw=2)  

# initialization function: plot the background of each frame
def init():
    line.set_data([], [])
    return line,

# animation function.  This is called sequentially
def animate(i):
    x = np.linspace(0, WindowDurSec, sampPerWindow)
    start = i*sampPerFrame
    stop = start + sampPerWindow
    step = 1
    y = Y[start : stop : step]
    line.set_data(x, y)
    return line,

# call the animator.  
anim = animation.FuncAnimation(fig, animate, init_func=init,
                               frames=passThruFrames, interval=frameDurMs, blit=True, repeat=False)

anim.save('sinewave_animation.mp4', fps=FPS, extra_args=['-vcodec', 'libx264'])

plt.show()

与理论相比，观察到的Matplotlib动画持续时间增加了一倍

0 个答案: