Blu-ray Video
Unlike DVD, Blu-ray supports SMPTE HD resolutions of 720p and 1080i/p with a display aspect ratio of 16:9 and a pixel aspect ratio of 1:1, so widescreen video is scaled non-anamorphically (this is referred to as "square" pixels).
An electrically coded video line (referred to as a field) is used in analog video transmission, recording and CRT displays, this can be sampled by a process called digitization which in professional SD video tape recorders is done at a rate of 720 pixels per field. This relates to the bandwidth used in digital serial connections and have come to be inaccurately called "rectangular" pixels. So called "square" pixels used to display 4:3 graphics and text on VGA CRTs are at 640x480 which excludes the sync pulses and blanking used in the field output. Therefore, to display a NTSC SD 4:3 capture of 720x480 you would have to crop the 8 pixels that are used for blanking off of each side and then "anamorphic-ally" scale the result to 640x480. Squeezing to create a 16:9 frame only does a good job of delivering widescreen with reasonable quality using standard 4:3 equipment when the compressed bit rate is high enough to avoid compression artifacts being noticed, as they are in a low rate MPEG-2 broadcast.
Blu-ray also supports anamorphic wide-screen, both at the DVD-Video/D-1 resolutions of 720×480 (NTSC) and 720×576 (PAL), and at the higher resolution of 1440×1080 (source aspect ratio of 4:3, hence a pixel aspect ratio of 4:3 = 16:9 / 4:3 when used as anamorphic 16:9). See Blu-ray Disc: Technical specifications for details.
Read more about this topic: Anamorphic Widescreen
Famous quotes containing the word video:
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