Jul 5

Practical HDV by:  mike

07/05/2005 03:51 PM

Pinnacle Systems White Paper HDV Simplified In September 2003 Canon Inc., Sharp Corporation, Sony Corporation, and Victor Company of Japan, Limited (JVC) announced that the specification which defines “the recording and playback of igh-definition video on a DV cassette tape has been established as the “HDV” format”. With this press release, HDV was born. It is now eighteen months after this announcement and both SONY and JVC are shipping several different models of HDV Camcorders. With a nice selection of camcorders available the next question to answer is “What do I need to know about HDV to edit it and more importantly to deliver finished pieces to customers?” What’s so special about HDV? HDV is much more than DV with a larger frame size. It uses a different codec to squeeze all of the extra pixels (HDV has approximately 5x the data as DV) into a data stream that ends up consuming the same amount of bandwidth as DV, 19-25 Mbits/sec. Instead of the “DV” codec, HDV uses a flavor of the MPEG-2 specification, MPEG IPB, to encode the video. MPEG IPB, also know as Long GOP MPEG, gives you great image quality at low data rates. To simplify how this happens, DV uses intraframe compression to compress data on a frame by frame basis. HDV uses intraframe and interframe compression to compress frames by comparing frames to themselves as well as to previous and future frames in your video sequence. The challenge with the MPEG IPB compression used to deliver HDV is that it uses a codec that does not mathematically describe every single video frame. The low data rate is possible because the codec checks for possible compression within each frame and it also checks the differences from one frame to another. MPEG IPB defines full frames of video once or twice per second. The results are great. All the Hollywood produced DVDs that you own use the same compression technique to deliver DVD images in a 6Mbit/sec stream. Editing a native HDV Stream Because MPEG IPB encodes one or two full frames every second, to edit native HDV streams you need to do some math. The great news about choosing Liquid Edition to edit your native HDV stream is that we are great at math. We are able to do the math and deliver full frames of video wherever you want, whenever you want. read more...


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