This patch accounts for the different size when proxy size of less that 100% is used
I would be much happier, if we could use get_proxy_filename() from indexer.c in this case we are creating new code to "emulate" it's
Also there was this switch when you use proxy per project or per strip
This line will have impact on performance - it will have to decode (most likely) several frames.
I guess this function could be quite streamlined.
I guess, that you have re-used this function to determine, if the proxy file exists.
In that case, you should rename it.