video - 有没有办法在 ffmpeg 的过滤器中使用当前帧和总帧作为变量？

Question

我正在尝试编写一个愚蠢的命令来顺时针旋转整个视频。我唯一需要的是一个变量来告诉过滤器当前帧数和总帧数。
这是我计划的命令(cf = 当前帧，tf = 总帧数)ffmpeg -i input.mp4 -vf rotate=(cf*(tf/360))/PI*180 output.mp4有没有人愿意帮忙？

Answer 1

rotate filter documentation 说:

The expressions for the angle and the output size can contain thefollowing constants and functions:

• n is the sequential number of the input frame, starting from 0. It is always NAN before the first frame is filtered.
• t is time in seconds of the input frame, it is set to 0 when the filter is configured. It is always NAN before the first frame isfiltered.

总持续时间没有变量，但您可以使用 ffprobe 获取输入文件持续时间。见 How to get video duration in seconds?
在 10 秒内完成 1 次顺时针旋转的示例:

ffmpeg -i input.mp4 -vf "rotate=(2*PI*t)/10" -c copy output.mp4