ffmpeg - 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”。我解决了这个问题:scale=-2:720。
之间有什么区别

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.