你可以“流”吗图像到ffmpeg构建视频，而不是将其保存到磁盘？ [英] Can you "stream" images to ffmpeg to construct a video, instead of saving them to disk?

问题描述

我的工作最近涉及以编程方式制作视频。在python中，典型的工作流程如下所示：

My work recently involves programmatically making videos. In python, the typical workflow looks something like this:

import subprocess, Image, ImageDraw

for i in range(frames_per_second * video_duration_seconds):
    img = createFrame(i)
    img.save("%07d.png" % i)

subprocess.call(["ffmpeg","-y","-r",str(frames_per_second),"-i", "%07d.png","-vcodec","mpeg4", "-qscale","5", "-r", str(frames_per_second), "video.avi"])

此工作流创建一个图像视频中的每个帧并将其保存到磁盘。在所有图像保存完毕后，ffmpeg将被调用以构建所有图像的视频。

This workflow creates an image for each frame in the video and saves it to disk. After all images have been saved, ffmpeg is called to construct a video from all of the images.

将图像保存到磁盘（而不是在内存中创建图像）在这里消耗大部分的周期，似乎没有必要。有没有办法执行相同的功能，但不保存图像到磁盘？因此，ffmpeg将被调用，并且构造后立即将ffmpeg映像进行构造。

Saving the images to disk (not the creation of the images in memory) consumes the majority of the cycles here, and does not appear to be necessary. Is there some way to perform the same function, but without saving the images to disk? So, ffmpeg would be called and the images would be constructed and fed to ffmpeg immediately after being constructed.

推荐答案

加工。感谢LordNeckbeard建议使用image2pipe。我不得不使用jpg编码而不是 png，因为image2pipe with png在我的ffmpeg ver.6上不起作用。第一个脚本基本上与您的问题的代码相同，除了我实现了一个简单的图像创建，只是创建从黑色到红色的图像。我还添加了一些代码来执行。

Ok I got it working. thanks to LordNeckbeard suggestion to use image2pipe. I had to use jpg encoding instead of png because image2pipe with png doesn't work on my verision of ffmpeg. The first script is essentially the same as your question's code except I implemented a simple image creation that just creates images going from black to red. I also added some code to time the execution.

串行执行

import subprocess, Image

fps, duration = 24, 100
for i in range(fps * duration):
    im = Image.new("RGB", (300, 300), (i, 1, 1))
    im.save("%07d.jpg" % i)
subprocess.call(["ffmpeg","-y","-r",str(fps),"-i", "%07d.jpg","-vcodec","mpeg4", "-qscale","5", "-r", str(fps), "video.avi"])

并行执行（没有保存图像到磁盘）

import Image
from subprocess import Popen, PIPE

fps, duration = 24, 100
p = Popen(['ffmpeg', '-y', '-f', 'image2pipe', '-vcodec', 'mjpeg', '-r', '24', '-i', '-', '-vcodec', 'mpeg4', '-qscale', '5', '-r', '24', 'video.avi'], stdin=PIPE)
for i in range(fps * duration):
    im = Image.new("RGB", (300, 300), (i, 1, 1))
    im.save(p.stdin, 'JPEG')
p.stdin.close()
p.wait()

结果很有趣，我运行每个脚本3次来比较性能：
系列：

the results are interesting, I ran each script 3 times to compare performance: serial:

12.9062321186
12.8965060711
12.9360799789

parallel：

8.67797684669
8.57139396667
8.38926696777

所以似乎并行版本快了约1.5倍。

So it seems the parallel version is faster about 1.5 times faster.

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