从 python 生成电影而不将单个帧保存到文件 [英] Generating movie from python without saving individual frames to files

问题描述

我想从我在 matplotlib 中的 Python 脚本中生成的帧创建 h264 或 divx 电影.这部电影大约有 10 万帧.

I would like to create an h264 or divx movie from frames that I generate in a python script in matplotlib. There are about 100k frames in this movie.

在网络上的例子中[例如.1]，我只见过将每一帧保存为png然后在这些文件上运行mencoder或ffmpeg的方法.就我而言，保存每一帧是不切实际的.有没有办法获取从 matplotlib 生成的图并将其直接通过管道传输到 ffmpeg，而不生成中间文件?

In examples on the web [eg. 1], I have only seen the method of saving each frame as a png and then running mencoder or ffmpeg on these files. In my case, saving each frame is impractical. Is there a way to take a plot generated from matplotlib and pipe it directly to ffmpeg, generating no intermediate files?

使用 ffmpeg 的 C-api 编程对我来说太难了 [例如.2].此外，我需要一个具有良好压缩的编码，例如 x264，否则电影文件对于后续步骤来说太大了.所以坚持使用 mencoder/ffmpeg/x264 会很棒.

Programming with ffmpeg's C-api is too difficult for me [eg. 2]. Also, I need an encoding that has good compression such as x264 as the movie file will otherwise be too large for a subsequent step. So it would be great to stick with mencoder/ffmpeg/x264.

有什么可以用管道做的事情[3]吗?

Is there something that can be done with pipes [3]?

[1] http://matplotlib.sourceforge.net/examples/animation/movie_demo.html

[2] 如何使用 x264 C API 将一系列图像编码为 H264?

[3] http://www.ffmpeg.org/ffmpeg-doc.html#SEC41

推荐答案

这个功能现在(至少从 1.2.0 开始，也许是 1.1)通过 MovieWriter 类被烘焙到 matplotlib 中，它是子- animation 模块中的类.您还需要提前安装ffmpeg.

This functionality is now (at least as of 1.2.0, maybe 1.1) baked into matplotlib via the MovieWriter class and it's sub-classes in the animation module. You also need to install ffmpeg in advance.

import matplotlib.animation as animation
import numpy as np
from pylab import *


dpi = 100

def ani_frame():
    fig = plt.figure()
    ax = fig.add_subplot(111)
    ax.set_aspect('equal')
    ax.get_xaxis().set_visible(False)
    ax.get_yaxis().set_visible(False)

    im = ax.imshow(rand(300,300),cmap='gray',interpolation='nearest')
    im.set_clim([0,1])
    fig.set_size_inches([5,5])


    tight_layout()


    def update_img(n):
        tmp = rand(300,300)
        im.set_data(tmp)
        return im

    #legend(loc=0)
    ani = animation.FuncAnimation(fig,update_img,300,interval=30)
    writer = animation.writers['ffmpeg'](fps=30)

    ani.save('demo.mp4',writer=writer,dpi=dpi)
    return ani

动画

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