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Show all posts by userPost here if you are having issues with Apple Compressor, codec and format conversions, making files for the web, or issues or questions with other compression programs.
Re: Question about H.264 - 13 years agoHarry, as you surmised, H.264 comes in a wide variety of flavors. There can be 4:2:2 H.264. Canon chose to use 4:2:0. Also H.264 coding isn't always heavily compressed. It depends (mostly) on the bitrate chosen. This might be 2 Mb/s for a YouTube piece, or 35 Mb/s for a Blu-ray disc, or using the Compressor preset for QT file in codec H.264 around 95 Mb/s. Canon chose a bitrate of around 44by dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuoteD-Mac To test only the monitor, you need to have a verified signal going into the monitor and a valid way to test its display. You're absolutely right that to test only the monitor you must start with a "verified signal". I'm sorry if I induced misunderstanding by sometimes saying I'm verifying the display. I should have said I'm verifying the display of the video. I'm inby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuoteD-MacYou can't cheat "physics." Agree. QuoteD-MacYour measurement technique is probably also invalid. To sample a video signal being displayed on a monitor (at a given frame rate), you need to consider the Nyquist frequency for proper signal resolution, and use a sufficiently long enough sampling to yield a valid set of samples. Nyquist's theorem pertains to the instantaneby dcouzin - Café LA Re: AVDHC mts files skip frames once transcoded to PRORES 422 - 13 years agoQuotebluey Now that is interesting, so this software i've used has or could have potentially degraded my shots a generation? i do have quite a good eye for image quality, noise, resolution and haven't noticed a lacking compared to the original files. You must add a generation when making ProRes 422 from AVCHD. The AVCHD is coded with interframe compression and ProRes 422 is purely intraframeby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agostrypes, I think the Apple monitor calibration can true up gain curves and yield neutrals, but it can't possibly correct for the hue shifts resulting from two monitors having different primaries. Nowhere in the Apple procedure do you decide "I want that green not that other green", etc. An instrument-aided calibration, aimed at standards, should be able to make those decisions and a cby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuotestrypesAlso, is QuickTime able to accurately map color spaces? I have a cheap Samsung monitor and I can't calibrate it to resemble an H-IPS display in the same color space, much less a broadcast monitor. Last time I tried working on a non broadcast monitor (don't ask, but there are houses who are too cheap to buy a broadcast monitor), my colors were off by a mile and a half when I was goingby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuoteJude Cotter Y'CbCr is not a colour space, really. It's a way of encoding RGB information. QuoteJude Cotter Y'CbCr is not an absolute colour space. But whatever. Absolute Schmabsolute! RGB isn't an absolute color space either. Its primaries must be specified to make it absolute. But once that's done Y'CbCr is made an absolute color space via the BT.709 inverse transforms (or whatever) aby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agostrypes, I get your point, that critical color viewing involves viewing more than color, for example, noise. I also agree that there may be gamut limitations with cheap monitors. In order to be brighter they choose more efficient primaries, reducing the triangle size. But I'm surprised that the color reproduction well away from the boundary can't be profiled to near perfection. Color sciby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuotestrypesYes. No. You technically cannot view y'cbcr as that needs to be transformed into rgb primaries for display. The FSI monitors have built in LUTs to do the conversion between certain color profiles accurately. I understand the Yes, but am unsure what the No is for. Are ICC profiles based on equations instead of lookup tables? Does this make ICC profiles too slow to accomplish converby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuoteJude CotterY'CbCr is not a colour space, really. It's a way of encoding RGB information. Y'CbCr is a color space, really. Look at L*a*b*, which the CIE (for heaven's sake) calls a color space. Y'CbCr strongly resembles L*a*b*. (Some differences are described on pages 6-8 of this primer). Sure there are equations for encoding RGB into Y'CbCr, but there are also equations for encoding X,Yby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuotestrypesThe graphics card will NOT send a y'cbcr signal from a y'cbcr source. A capture card does just that over an HD-SDI signal. Yes the .mov file is usually in Y'CbCr and the graphics card converts this to a RGB signal. But the monitor (or projector) itself is RGB. So at some point the Y'CbCr must be transformed to R'G'B' and finally to RGB. As you describe it, the capture card is doingby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoJude, high speed photography? There is no high speed photography suggested. That would require specialized equipment. I'm setting out a method which anyone who owns a digital still camera (with adjustable shutter) and who can make a simple test video, can use to check whether a monitor or projected display is frame-accurate 60p. The method can be modified for other frame rates. Minutiae?by dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years ago(dedicated to Anita L.) There seem to be just three ways a display can screw up frame rate: skip a frame show a frame more than once blend frames for the full duration of a frame for just a part of the duration of a frame The original short shutter speed snapshot method detects artifact 3 but can't distinguish between artifacts 3a and 3b. The long (1/50 sec) shutter speed snapshot methodby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agostrypes, does the I/O card bypass the graphics card and send what FCP reads directly to the monitor, filling the screen with the video? Which ones do you recommend? Dennis Couzin Berlin, Germanyby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuoteD-MacI would be more interested if you were trying to test an actual external broadcast monitor connected to the computer via a video I/O card, since that is really the only proper way to monitor your video. Anything displayed on a computer monitor connected via DisplayPort or DVI to a computer is going to provide only a proxy image and never close to the actual thing. This is the part I dby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoSome kinds of film rate artifacts are easily and unambiguously tested by the snapshot method. Make a test film image consisting of a white dot which moves a certain amount with each new frame. (For convenience, progressive numbers can replace dots.) Snapshots shot with 1/50 second shutter will usually (80% chance) receive exposure from two consecutively displayed 60p video frames and lessby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoQuoteD-Mac Wrote: You should really read the article I linked to in a previous post. Ignore the mentioning of the company's media player product and just focus on the technical aspects. The article presumes that the monitor has a fixed refresh rate, which obviously magnifies the task of the genlocker. Is this how things really work? QuoteD-Mac Wrote:The vertical refresh rate of your monby dcouzin - Café LA Re: Unfound Codec Hardware..... what? - 13 years agoD-Mac Wrote: ------------------------------------------------------- > If 854 x 480 is what is extracted from a 720 x 480 > image on the DVD, how is it really "down rez'd" > when put back into a SD frame size sequence (720 x > 480). Why wouldn't you simply extract the material > "properly" as 720 x 480 from the DVD and just use > that? Whoever did tby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agostrypes, your suggestion of the LCD's slow response explains the apparent frame blending seen in a fraction of the snapshots. The target has white numbers on a black background. Going from the '0' frame to the '1' frame all the pixels in the '0' must go from white to black and all the pixels in the '1' must go from black to white. Since these states are determined by the twist of a liquid crysby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoThanks Loren. Sure enough FCP User Prefs > Render Settings > Frame Blending for Speed was checked. But unchecking it did not eliminate the blended frames in either the FCP viewer or canvas. Strangely, atMonitor reported 64-76 fps while playing the 60p clip in FCP. Also strangely, atMonitor reported 54-60 fps while playing a 50p clip in QuickTime. (QuickTime reported 49-51 fps.) So Iby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agostrypes, I was careful to make the target small in the center of the frame to avoid any such shutter problems. (Indeed I began the experiment shooting the monitor with a CMOS camcorder, also with short shutter speed set. The camcorder being 50p and the monitor being 60Hz killed that idea.) Dennis Couzin Berlin, Germanyby dcouzin - Café LA Re: Unfound Codec Hardware..... what? - 13 years agoI just set up a 854x480 ProRes sequence in FCP 7.0.3 and encountered no difficulty rendering effects. My OS is 10.5.8, unlike Kozikowski's 10.6.6. 854x480, even if ripped from a DVD, shouldn't be unnecessarily down-rez'd. Dennis Couzin Berlin, Germanyby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoDave, thanks for the many good suggestions. I'll try atMonitor and hope of course that MediaMaster Pro (auxiliary software genlock) isn't needed. My main interest isn't so much monitor viewing as projection. There is need for a practical versatile routine for playing various video files on various video projectors. (Can the FCP viewer be full screen?) 3 DLP projectors should be best and imby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agostrypes, good thought. My monitor response time (GTG) is specified at 6 ms. If the black-->white and white-->black times are on that order it could explain much of what I'm seeing. Dennis Couzin Berlin, Germanyby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoDave, MPEG Streamclip yielded the same blend frames from the 720p60 file, as did the viewer of FCP. The computer system is an old Mac Pro with four 2.6 GHz cores, 7 GB RAM, OS 10.5.8, no extraneous processes. Should this be suspected? FCP does not report RT failure. The graphics card is Nvidia 8800 GT. Should this be suspected? The monitor is a Samsung 305T. Should this be suspectby dcouzin - Café LA Re: QuickTime playback framerate artifacts - 13 years agoLoren and Dave, yes this is about system resources. Converting the test video to codec "None" (uncompressed 8-bit R,G,B) on a RAM drive and playing with QuickTime did result in fewer departures from reported 60 fps playback (but still the occasional 59 and 61). Yet there were way too many snapshots (now with shutter speed 1/1600 sec) showing double images. Perhaps QuickTime can holdby dcouzin - Café LA QuickTime playback framerate artifacts - 13 years agoWhen I play a 720p60 .mov file with QuickTime its playback speed bounces around between 59 and 61 according to Inspector. The sound playback speed must be steadier or this would be annoying. The less than ±2% variation in picture speed should not itself be visible, and the bouncing is fast enough that sound synch stays within one frame. However, you have to wonder HOW the playback speed canby dcouzin - Café LA Re: Can I ONLINE-EDIT in Broadcast Quality with FCP? - 13 years agoThe analogy --- silver-on-paper photo : digital photo file :: videotape : digital video file --- won't fly. A silver-on-paper photo bears the undisguised picture. If it fades a bit or some flecks pop off, the picture mostly survives. Both the videotape and the digital files bear/contain coded pictures. What lies nearby in the code does not generally lie nearby in the picture, and codes themseby dcouzin - Café LA Re: Looking for Good Esata Card for MacPro1, 1 - 13 years agoI tried the LaCie SATA II PCI Express card on my MacPro 1.1 and it worked poorly, especially with drives plugged into both of its ports. (It looks like generic junk, not even branded by LaCie.) I replaced it with the Sonnet Tempo SATA E2P PCI Express card, which has been trouble-free. Yes this LaCie and this Tempo are based on the same chip, but they're not the same. Dennis Couzin Berlin,by dcouzin - Café LA Re: Frame skipping effect - 13 years agoIt can be done by two passes through Compressor. First set rate conversion at 33.333%. Second set rate conversion at 300%. Both times use Fast (nearest frame). That way you can pretend you invented the effect. Seriously, double passes through Compressor, the first doing something, the second undoing it, is a generally useful technique for effects. Dennis Couzin Berlin, Germanyby dcouzin - Café LA |
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