Vídeo de alta definición (HD)

High-definition (HD) video refers to any video format with pixel dimensions greater than those of standard-definition (SD) video formats. Typically, standard-definition refers to digital formats with pixel dimensions close to those of analog TV standards, such as NTSC and PAL (around 480 or 576 vertical lines, respectively). The most common HD formats have pixel dimensions of 1280x720 or 1920x1080, with a widescreen aspect ratio of 16:9.

HD video formats include interlaced and noninterlaced varieties. Typically, the highest-resolution formats are interlaced at the higher frame rates, because noninterlaced video at these pixel dimensions would require a prohibitively high data rate.

You can reap benefits from shooting and editing in high-definition formats even if you output to standard definition. For example, the quality of high-definition clips remains high when you zoom into them or pan across them in the context of standard-definition projects.

HD video formats are designated by their vertical pixel dimensions, scan mode, and frame or field rate (depending on the scan mode). For example, 1080i60 denotes interlaced scanning of 60 interlaced 1920x1080 fields per second, whereas 720p30 denotes progressive scanning of 30 noninterlaced 1280x720 frames per second. In both cases, the frame rate is approximately 30 frames per second.

Programs in Adobe Creative Suite Production Premium includes presets that are designed for working with various high-definition formats. Some of the most common high-definition video formats you may encounter include the following:

AVCHD (Advanced Video Codec High Definition): High-definition format based on an MPEG-4 AVC video codec for file-based (tapeless) camcorders. AVCHD was introduced by Sony and Panasonic.
DVCPRO HD: Panasonic’s high-definition variant of its DVCPRO format, which also includes DVCPRO25 and DVCPRO50. Whereas DVCPRO25 and DVCPRO50 support data rates of 25 Mbits/s (megabits per second) and 50 Mbit/s, respectively, DVCPRO HD supports a data rate of 100 Mbit/s, from which it gets its other name, DVCPRO100. DVCPRO HD footage can be captured to Panasonic P2 media.
HDCAM: Sony’s high-definition version of its Digital Betacam format. A variant called HDCAM SR uses a tape with a higher particle density to record video with greater color sampling and at higher bit rates. However, HDCAM SR is supported by decks only, and not camcorders.
XDCAM HD and XDCAM EX: High-definition formats developed by Sony for file-based (tapeless) camcorders.
HDV: Developed jointly by several companies, HDV employs a form of MPEG‑2 compression to enable high-definition video to be encoded onto standard miniDV cassette media.
H.264: Also known as MPEG‑4 part 10 and AVC (Advanced Video Coding), H.264 can deliver video over a range of bitrates more efficiently than previous standards. For example, H.264 can deliver the same quality as MPEG‑2 at half the data rate. H.264 is built into the Apple QuickTime 7 multimedia architecture, and it’s supported by the Blu‑ray Disc format.
Uncompressed HD: High-definition video in an uncompressed format. Without compression to reduce the video’s data rate, uncompressed video requires relatively fast computer processors, hard disks, and a specialized capture device.
WM9 HDTV: Microsoft’s high-definition delivery format is among numerous formats included in the Windows Media 9 (WM9) framework. By employing an aggressive compression scheme, WM9 HDTV permits high-definition video encoding and playback at relatively low data rates.

For more information about high-definition video, see A Digital Video Primer: Understanding and Using High-Definition Video at www.adobe.com/go/learn_dv_primer_highdef_en.