使用ffmpeg从视频中提取图片

项目需求：将一段视频按照每秒一帧进行图片提取，搜索到方法“ffmpeg –i test.avi –r 1 –f image2 image-%3d.jpeg”，实际使用中报错
“[NULL @ 0x7fa696801000] Unable to find a suitable output format for ‘–i’
–i: Invalid argument”
一、stackoverflow搜索到解决方法，记录如下：
”–”≠”-”，上述方法中的“–i”使用的是em dash,正确的应该是使用hyphen,详细区别可以查看知乎文章：https://www.zhihu.com/question/20332423/answer/15370327

二、从ffmpeg官网查到方法，“ffmpeg -i foo.avi -r 1 -s WxH -f image2 foo-%03d.jpeg”，This will extract one video frame per second from the video and will output them in files named foo-001.jpeg, foo-002.jpeg, etc. Images will be rescaled to fit the new WxH values.

If you want to extract just a limited number of frames, you can use the above command in combination with the -vframes or -t option, or in combination with -ss to start extracting from a certain point in time.