FFMPEG 选项 scale=-1 和 scale=-2

Question

我尝试转换视频并使用 scale=-1:720 调整其大小，但出现错误“宽度不能被 2 整除”。我用：scale=-2:720 解决了这个问题。

有什么区别

scale=-1:720

和

scale=-2:720

Answer 1

它在 the documentation:

If one and only one of the values is -n with n >= 1, the scale filter will use a value that maintains the aspect ratio of the input image, calculated from the other specified dimension. After that it will, however, make sure that the calculated dimension is divisible by n and adjust the value if necessary.

Answer 2

如果您将 -1 和 -2 视为 -n，那么这会将指定的尺寸（宽度、高度）设置为 n 的倍数。