The most common source of LDTV programming is the Internet, where mass distribution of higher-resolution video files could previously overwhelm computer servers and take too long to download. Many mobile phones and portable devices such as Apple’s iPod nano, or Sony’s PlayStation Portable use LDTV video, as higher-resolution files would be have no perceivable advantage when viewed on their low resolution displays (320×240 and 480×272 pixels respectively). The 3rd, 4th, 5th, and 7th generation of iPod nano has an LDTV screen, as do the first three generations of iPod touch and iPhone (480×320).