问题描述
有人知道将数组中存储的像素值序列保存到视频的方法吗?目前，我正在使用Cimg可视化一个简单的n体模拟，尽管我可以将每次迭代保存到一个图像文件中，但这非常慢.对于处理视频的类似库的任何建议将不胜感激.本质上，我只想将创建的Cimg窗口中显示的内容记录到视频文件中.该程序是用Linux上的C ++编写的，并使用g ++进行编译.
Does anyone know of a method to save a sequence of pixel values, stored in an array to a video? Currently I'm using Cimg to visualise a simple n-body simulation, whilst I can save each iteration to an image file, this is very slow. Any suggestions on a similar library for handling video would be appreciated. Essentially, I just want to record what's displayed in the Cimg window I create to a video file. The program is written in C++, on linux, compiling with g++.
我可以运行模拟并使用屏幕捕获软件将其记录下来，这一事实似乎暗示有可能，但是我想要一个更简洁的解决方案.
The fact that I can run the simulation and record it running with screen capturing software would seem to imply it's possible, but I'd like a tidier solution.
干杯，安格斯
推荐答案
我今天正在玩这个游戏，并以为我会分享我的结果.您可以从 CImg 输出原始RGB视频，然后使用 ffmpeg 将其编码为如下视频:
I was playing around doing this today, and thought I would share my results. You can output raw RGB video from CImg and then use ffmpeg to encode it up into video like this:
#include <iostream>
#include "CImg.h"
using namespace std;
using namespace cimg_library;
int main()
{
const unsigned int width=1024;
const unsigned int height=768;
// Basic frame we will draw in
CImg<unsigned char> image(width,height,1,3);
unsigned char magenta[] = {255,0,255};
// We are going to output 300 frames of 1024x768 RGB raw video
// ... making a 10s long video at 30fps
int radius=100;
int cx=100;
int cy=100;
for(int frame=0;frame<300;frame++){
// Start with black - it shows fewer stains ;-)
image.fill(0);
image.draw_circle(cx,cy,radius,magenta);
// Move and re-colour circle
cx+=2; cy++; if(magenta[1]!=255){magenta[1]++;}
// Output to ffmpeg to make video, in planar GBR format
// i.e. run program like this
// ./main | ffmpeg -y -f rawvideo -pixel_format gbrp -video_size 1024x768 -i - -c:v h264 -pix_fmt yuv420p video.mov
char* s=reinterpret_cast<char*>(image.data()+(width*height)); // Get start of G plane
std::cout.write(s,width*height); // Output it
s=reinterpret_cast<char*>(image.data()+2*(width*height)); // Get start of B plane
std::cout.write(s,width*height); // Output it
s=reinterpret_cast<char*>(image.data()); // Get start of R plane
std::cout.write(s,width*height); // Output it
}
}
我想我不会去好莱坞，因为视频不是很刺激！
I guess I won't make it to Hollywood as the video is not very exciting!
像上面那样运行上面的代码来制作视频:
Run the above code like this to make a video:
./main | ffmpeg -y -f rawvideo -pixel_format gbrp -video_size 1024x768 -i - -c:v h264 -pix_fmt yuv420p video.mov
注释1
要实现的是 CImg 以平面配置存储数据，这意味着首先是所有红色像素，然后是所有绿色像素，然后是所有蓝色像素，然后是所有蓝色像素.没有任何填充或空格.
The thing to realise is that CImg stores data in a planar configuration, which means all the red pixels first, then all the green ones directly afterwards and then all the blue ones straight after that - all without any padding or spaces.
想象一下CImg中的4x4图像(具有16个像素):
Imagine a 4x4 image (with 16 pixels) in CImg:
RRRRRRRRRRRRRRRR GGGGGGGGGGGGGGGG BBBBBBBBBBBBBBBB
与常规RGB数据不同，常规RGB数据将存储与以下图像相同的图像:
unlike regular RGB data, which would store the same image as:
RGB RGB RGB RGB RGB RGB RGB RGB RGB RGB RGB RGB RGB RGB RGB RGB
因此，您可以重新整理周围的所有数据并将其重新格式化，然后以-pixel_fmt rgb24的形式传递给 ffmpeg ，或者按照我的方式进行操作，并在 CImg 平面格式，然后选择匹配的-pixel_fmt gbrp(其中p表示平面" ).您只需要按照正确的B，G，R顺序输出平面.另请参见注释4 .
So, you can either shuffle all the data around and reformat it and pass to ffmpeg as -pixel_fmt rgb24, or do as I did and output in CImg's planar format and choose a matching -pixel_fmt gbrp (where the p means "planar"). You just have to output the planes in the correct B,G,R order. See also Note 4.
注释2
我选择执行3个write()，每个颜色平面一个，为了便于说明，将聚集写入" 与writev()一起使用会更有效. ，因此:
I chose to do 3 write()s, one for each colour plane, for the sake of clarity of demonstration, it would be more efficient to use a "gathered write" with writev(), so this:
char* s=reinterpret_cast<char*>(image.data()+(width*height)); // Get start of G plane
std::cout.write(s,width*height); // Output it
s=reinterpret_cast<char*>(image.data()+2*(width*height)); // Get start of B plane
std::cout.write(s,width*height); // Output it
s=reinterpret_cast<char*>(image.data()); // Get start of R plane
std::cout.write(s,width*height);
将变成(未经测试)的样子:
would become something like (untested):
struct iovec iov[3];
ssize_t nwritten;
iov[0].iov_base = reinterpret_cast<char*>(image.data()+(width*height))
iov[0].iov_len = width*height;
iov[1].iov_base = reinterpret_cast<char*>(image.data()+2*(width*height));
iov[1].iov_len = width*height;
iov[2].iov_base = reinterpret_cast<char*>(image.data());
iov[2].iov_len = width*height;
nwritten = writev(STDOUT_FILENO,iov,3);
注释3
我使用-c:v h264 -pix_fmt yuv420p使视频与Mac上的Apple QuickTime 兼容，但是无论如何您都可以轻松更改输出-更难的部分是获得 CImg 和 fmpeg .
I used the -c:v h264 -pix_fmt yuv420p to make the video compatible with Apple's QuickTime on my Mac, but you can change the output easily anyway - the harder part was getting the interface between CImg and fmpeg right.
注释4
如果您想重新整理数据并将其写到 ffmpeg 非平面(-pixel_fmt rgb)，我本来就是这样做的，并且代码是这样的:
If you want to shuffle the data around and write it to ffmpeg non-planar (-pixel_fmt rgb), I did that originally and the code was like this:
// Outside main loop
unsigned char* BIP = new unsigned char[width*height*3];
unsigned char *d,*r,*g,*b;
...
...
// Now output it...
// ... remember CImg is band-interleaved by plane RRRRRR GGGGGG BBBBBB
// ... not band-interleaved by pixel RGB RGB RGB RGB
r=image.data(); // Start of R plane in CImg image
g=r+(width*height); // Start of G plane in CImg image
b=g+(width*height); // Start of B plane in CImg image
d=BIP; // Destination buffer in RGB order
for(int i=0;i<width*height;i++){
*d++=*r++;
*d++=*g++;
*d++=*b++;
}
// Output to ffmpeg to make video, i.e. run program like this
// ./main | ffmpeg -y -f rawvideo -pixel_format rgb24 -video_size 1024x768 -i - -c:v h264 -pix_fmt yuv420p video.mov
std::cout.write(reinterpret_cast<char*>(BIP),width*height*3);
理论上，您可以使用 CImg 的permute_axes()方法执行此操作，但我没有成功.
In theory, you can do this with CImg's permute_axes() method, but I had no success.
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