我一直在试图弄清楚如何使用 FFmpeg 旋转视频。我正在处理以纵向模式拍摄的 iPhone
视频。我知道如何使用MediaInfo（优秀的库，顺便说一句）确定当前的旋转度数，但我现在被困在
FFmpeg 上。

根据我的阅读，您需要使用的是 vfilter 选项。根据我所看到的，它应该是这样的：

ffmpeg -vfilters "rotate=90" -i input.mp4 output.mp4

但是，我无法让它工作。首先， -vfilters 不再存在，现在只是 -vf 。其次，我收到此错误：

No such filter: 'rotate'
Error opening filters!

据我所知，我有一个全选项的 FFmpeg。运行 ffmpeg -filters 显示：

Filters:
anull            Pass the source unchanged to the output.
aspect           Set the frame aspect ratio.
crop             Crop the input video to x:y:width:height.
fifo             Buffer input images and send them when they are requested.
format           Convert the input video to one of the specified pixel formats.
hflip            Horizontally flip the input video.
noformat         Force libavfilter not to use any of the specified pixel formats
 for the input to the next filter.
null             Pass the source unchanged to the output.
pad              Pad input image to width:height[:x:y[:color]] (default x and y:
 0, default color: black).
pixdesctest      Test pixel format definitions.
pixelaspect      Set the pixel aspect ratio.
scale            Scale the input video to width:height size and/or convert the i
mage format.
slicify          Pass the images of input video on to next video filter as multi
ple slices.
unsharp          Sharpen or blur the input video.
vflip            Flip the input video vertically.
buffer           Buffer video frames, and make them accessible to the filterchai
n.
color            Provide an uniformly colored input, syntax is: [color[:size[:ra
te]]]
nullsrc          Null video source, never return images.
nullsink         Do absolutely nothing with the input video.

拥有vflip 和 hflip 的选项非常棒，但它们不会让我到达我需要去的地方。我需要至少能够将视频旋转 90 度。270
度也是一个很好的选择。旋转选项哪里去了？