FFMPEG:每5秒从直播流中提取一个帧 [英] FFMPEG: extract a fram from a live stream once every 5 seconds

问题描述

我正在尝试从实时流中每5秒提取一次帧，而无需使用-vf选项.我正在使用Raspberry Pi，因此CPU至关重要.

I'm tryin gto extract a single frame from a live stream, every 5 seconds without using the -vf option. I'm using a Raspberry Pi so CPU is all important.

基本上，我正在从实时源流式传输UDP流，该源使用的CPU很少，但是我想每5秒拍摄一次快照.

Basically, I'm streaming a UDP stream from a live source, which uses very little CPU but I want to take a snapshot every 5 seconds.

这有效，但仅产生单个图像.

This works, but only produces a single image.

-c copy -f mpegts udp://239.0.0.1:1234 -vcodec copy -vframes 1 out.png

这有效，但是使用了所有CPU和更多CPU.

This works, but uses all the CPU and more.

-c copy -f mpegts udp://239.0.0.1:1234 -vcodec copy -vf fps=1 out%d.png

有人知道我是否可以不使用过滤器来做到这一点吗?我的另一个解决方案是运行第二个ffmpeg并连接到UDP流，这确实很麻烦.

Anyone know if I can do this without using a filter? My other solution is to run a second ffmpeg and connect to the UDP stream, which is really cumbersome.

推荐答案

由于关键帧是每秒一帧，并且您希望每5秒一帧，因此需要进行一些过滤，除非您可以从每5个中删除4个就可以了图片已创建.

Since your keyframes are one per second, and you want one frame every 5 seconds, some filtering is needed, unless you are okay with deleting 4 out of every 5 images created.

这里是假设关键帧间隔为1/s的情况下，每5秒创建一帧的模板.

Here's the template that creates one frame for every 5 seconds, assuming that keyframe interval is 1/s.

ffmpeg -i ... -c copy -map 0 -f tee "[f=mpegts]udp://239.0.0.1:1234|[f=mpegts]pipe:" | ffmpeg -f mpegts -skip_frame nokey -i pipe: -vf select='not(mod(n,5))' -vsync 0 out%d.png

这是将每个关键帧作为图像转储，然后删除不需要的关键帧:

and here's for dumping each keyframe as an image and then removing unneeded ones:

ffmpeg -i ... -c copy -map 0 -f tee "[f=mpegts]udp://239.0.0.1:1234|[f=mpegts]pipe:" | ffmpeg -f mpegts -skip_frame nokey -i pipe: -vsync 0 out%d.png

管道语法pipe:在Windows上适用.相信它也可以在linux上运行.

The piping syntax pipe: works here on Windows. Believe it should work on linux as well.

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