Polkast does not modify your original files. We do automatically generate thumbnails of your photos and videos to give you a better user experience. Polkast also resamples photos as necessary so that they are optimized for the screen size and resolution of your mobile device, and for faster transmission to mobile devices. In a future release, Polkast will also transcode your videos so that they will play more effectively on mobile devices. Different mobile platforms only support specific kinds of video format. Along with making videos more compatible to more devices, transcoding them will make videos much smaller; therefore, faster to transport. To summarize, while we don't modify your original files, we do need to transform and transmit some of your files accordingly.