HDV

From Freepedia

HDV can also mean Hepatitis D virus.

Image:Sonyhdrfx1.jpg High Definition Video (HDV) is a video format designed to record high-definition video on standard DV media (DV or MiniDV cassette tape).

Contents

History

The HDV format was defined by four companies: Canon Inc., Sharp Corporation, Sony Corporation, and Victor Company of Japan, Limited (JVC). These companies originally announced their HDV partnership in September, 2003. They have since been joined by other companies, notably Apple Computer.

Overview

HDV was designed to offer existing video-production environments a cost-conscious path from SD to HD environments. HDV production equipment, being constrained to the 25Mbit/s bitstream rate of standard DV, is much less expensive than equipment based on professional standards such as HDCAM and DVCPROHD. HDV's main benefit is low-cost video acquisition, as HDV-camcorders can be built and operated at costs closer to conventional DV. This opens high-definition video acquisition to consumers, amateur videographers, and low-budget TV production.

In terms of compression strategy, DV and HDV are very different. In DV, the video-compression is purely intraframe (spatial). HDV, a constrained form of MPEG-2 video, employs both intraframe and interframe (temporal) techniques. The result is higher compression ratios than possible with a purely intraframe technique, but at the expense of increased artifacts. Editing HDV footage is also more difficult, due to the nature of MPEG-2 GOP (group of pictures) structure. In DV, as each frame of a video sequence is stored as an independent object, the recorded footage can be spliced at any frame, without disturbing adjacent footage. In HDV, many frames are encoded relative to adjacent keyframes. Any disturbance of the video, whether it be a complex transition or a simple scene-change, requires a decompression/recompression cycle of the entire HDV frame group. In practical terms, video editing is performed on a computer workstation with random-access storage, so the re-render process's only impact is slight video degradation at the splice point.

In HDV, the video frame is defined to have an aspect ratio of 16:9. Permitted resolutions are 720p and 1080i. In the case of 1080i, HDV uses a reduced sampling-resolution of 1440x1080, resulting in non-square pixels. Both HDCAM and DVCPROHD also use non-square pixels, so HDV footage can be imported into existing HD-production flows without undue additional difficulty.

Audio on HDV is lossy-compressed using high-bitrate MP2.

Since the bitrate of the HDV bitstream is the same as conventional DV25, recording-times for HDV are the same as for DV. That is, a 60 minute MiniDV cassette can store 60 minutes of either DV or HDV footage.

Apple's iMovie HD was the first consumer-level editing application with HDV support. Other video editing applications which have included support for HDV include Avid's Xpress Pro HD, Apple's Final Cut Express and Final Cut Pro 5, Pinnacle's Liquid Edition, Adobe's Premiere Pro, Canopus's Edius and Sony Pictures Entertainment's Vegas 6.0.

Specifications

MediaDV or MiniDV Tape
Video signal720/60p, 720/30p, 720/50p, 720/25p, 1080/60i, 1080/50i
CompressionMPEG2 Video (profile & level: MP@H-14)
Sampling frequency for Luminance74.25MHz 55.7MHz
Chroma subsampling4:2:0
Quantization8 bits (both luminance and chrominance)
Bit rate after compressionApproximately 19 Mbit/s/25 Mbit/s
Audio compressionMPEG1 Audio Layer II
Audio sampling frequency48kHz
Audio quantization16 bits
Audio bit rate after Compression384 kbit/s
Audio modeStereo (2 channels)
Stream typeTransport Stream Packetized Elementary Stream
Stream interfaceIEEE1394 FireWire (MPEG2-TS)

See Also

External links

Retrieved from "http://en.freepedia.org/HDV.html"


Views
Personal tools
Similar Links