The number is the signature pixel density (PPI) for Apple's original Retina Display .
: Usually paired with AAC-LC audio up to 160 Kbps. 3. "Deep Text" and Research 326 mp4
The standard video format for these 326 ppi devices is . The number is the signature pixel density (PPI)
: These devices natively play .mp4 , .m4v , and .mov files. and .mov files.