From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <40C827F5.2010707@chunder.com> Date: Thu, 10 Jun 2004 19:20:53 +1000 From: Bruce Ellis User-Agent: Mozilla Thunderbird 0.6 (Windows/20040502) MIME-Version: 1.0 To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu> Subject: Re: [9fans] A prick into the wasps' nest ;-) References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Topicbox-Message-UUID: 9b11fb22-eacd-11e9-9e20-41e7f4b1d025 i get really annoyed with badly mastered dvds, let alone crap players that are worse than VHS. i get agitated by a dropped frame, particularly an I frame, and will return the DVD as faulty if it happens in the "good bits". yeah i have 100Hz component which does more video formats than i have the ITUs for. even worse are the DVDs that slip lip-sync 'cause they are badly mastered. when the lips and the voice get 2 frames apart i give up. remarkable that i can master a DVD-R from DV - at a high bit rate and get no such problems. this has little to do with real-time, but ... the reason i added edf to the ps2 inferno kernel was so the double buffering was in sync with the retrace and the IDCT dmas were in time for the buffer. i think the linux guys are still working on it and are happy with 5 fps, 'cause it's a start ... brucee Nigel Roles wrote: >>factors involved. if we assume that TV is 26 (iirc) frames/second >>there is phosphor persistance on the the screen (let's forget about >>LCD's) and (iirc) there's retinal persistance. so, dropping a >>few frames doesn't really matter. oh yeah, it's interleaved as well. >> >>they may not even be watching when the frames are dropped. >> > > > Even if I softly drop a few words here and there, this is still > recognisably rubbish. > > The frame rate is 25Hz for PAL, or 30Hz for NTSC (29.97 for pedants). > SECAM is also 25 Hz. > > There is some persistance (sic), but the human eye/brain > is extremely sensitive to missing frames, or disturbed frame timing, > so it is arguable that persistence makes a timing error worse. > You only have to watch a someone walk across the shot on a decent > DVD player and then compare it will your typical soft decoder on > a Windows laptop to know that seeing all the fields at the right > time is a really important. > > Interleaving only helps reduce apparent flicker. Each field represents > a different point in time, so missing a field, or replacing one > with a copy of the previous one is ruinous. Swap the fields and > everything looks furry. 100Hz TVs don't just > display each field twice; they have a DSP in there to > sort out the motion compensation and synthesise the missing fields. > My 100Hz TV still screws up on fast scrolling credits (horizontal > and vertical). > > Stick to what you know, Boyd. > Except the guns; it's really, really tedious. > > >