I had submitted an entire package for windows to Roku about a year and a half ago to make available for users. I just don't have the hosting space for it. The short solution is to download VirtualDub, use the resize filter to get your SD images at 240x180, change the framerate to 'decimate by 240' for 23.97 fps video, or 10 * the framerate, select File/Export Image Sequence - for a 2-hour movie on a current powerful pc that shouldn't take more than 5-10 seconds, and then the biftool.exe file can combine all the images in a folder in less than a second into a valid bif file. Or you can custom-compile ffmpeg to do it as well, but it's more complicated to get the codecs you want for inclusion. If you are going the virtualdub method there is a plugin available to add mp4 support, which you will need, just be sure to grab the older version as it is 2-3 times faster than the current one. FFInputDriver_64 - dated 5/26/2014 seems to work fastest for me. Virtualdub also has scripting support to automate from command line.