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Newsgroups: alt.video.digital-tv
From: "Peter Harris" <peter.har...@bbc.co.uk>
Date: 1999/05/11
Subject: Re: EBU Technical Recommendation R92-1998
Hello Charlie.
Charlie Pearce <pea...@globalnet.NO-SPOO-PLEASE.co.uk> wrote in article > I recently found and read the above document, which has helped to 720 luminance pixels (digital active line) at 13.5MHz pixel-rate is a time > confuse me more than I was before about 625-line TV/DVB broadcasting: > The ITU BT.601 standard (digital TV) specifies a line length of 720 of 53.3 microseconds. Analogue video from a 625/50 blanked camera Y output will be 52 microseconds in width between half-amplitude points, so the analogue active-line period of a picture source is nominally 702 pixels. (702 x 1/13.5MHz = 52 micosecs). > My questions: The 18 other pixels allow for the rise and fall time of analogue blanking > 1. What are the other 18 pixels used for? Horizontal retrace, in the either side of the 52 microseconds nominal, and for any positional lee-way (mis-timing!) of the analogue video relative to digital syncs. There are 144 Y "pixel periods" of digital blanking period for H retrace, > 2. Are DVB broadcasts/European DVDs really 720x576 or actually according to analogue standards. So the occupied pixels of the digital active line are a nominal 702. Some encoders pre-filter and downsample to fewer pixels. This softens the picture, but reduces the input data per frame to the compressor. > 3. Does the 4x3 aspect ratio currently used refer to 720x576 pixels or analogue source picture, ie 702 pixels. With 16:9 pictures, the 702 pixels still make 52 microseconds of analogue waveform, but it is spread over 1/3 more screen width for the same image height. > 4. What about NTSC/US DTV? Are there 720 active picture information Try www.atsc.org? > pixels, or less? > 5. Where can I get hold of ITU documentation? The EBU website Regrettable but true! Try www.etsi.org/BROADCAST/ > contains plenty of papers, but the ITU site seems to imply you need to > be a paying subscriber :- > Thanks for any information Could I suggest a Digital Video Standards and Measurements course at BBC > Charlie Training, Wood Norton?! Peter - my thoughts not necessarily those of...... You must Sign in before you can post messages.
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