To use the proxy in a classic way, i.e. as a scaling, select \texttt{Settings $\rightarrow$ Proxy settings} and change the Scale factor from Original size to your downsized choice. You can choose ffmpeg as the File Format \index{file format} and a choice of various codecs associated with that. A good choice is the default of mpeg which can usually be quite fast. In addition, to modify values for that codec, click on the wrench icon.
To use the proxy in a classic way, i.e. as a scaling, select \texttt{Settings $\rightarrow$ Proxy settings} and change the Scale factor from Original size to your downsized choice. You can choose ffmpeg as the File Format \index{file format} and a choice of various codecs associated with that. A good choice is the default of mpeg which can usually be quite fast. In addition, to modify values for that codec, click on the wrench icon.