re quicktime performance was re rumours about do in article apr waikato ac nz ldo waikato ac nz lawrence d oliveiro waikato university writes path dime ymir cs umass edu nic umass edu noc near net howland reston ans net usc elroy jpl nasa gov decwrl waikato ac nz ldo from ldo waikato ac nz lawrence d oliveiro waikato university newsgroups comp multimedia comp graphics date apr gmt references mar aragorn unibe ch apr rchland ibm com organization university of waikato hamilton new zealand lines xref dime comp multimedia comp graphics ok with all the discussion about observed playback speeds with quicktime the effects of scaling and so on i thought i d do some more tests first of all i felt that my original speed test was perhaps less than realistic the movie i had been using only had frames in it it was a version of the very first movie i created with the compact video compressor i decided something a little longer would give closer to real world results for better or for worse i pulled out a copy of a space odyssey that i had recorded off tv a while back about fifteen minutes into the movie there s a sequence where the earth shuttle is approaching the space station specifically i digitized a portion of about seconds duration zooming in on the rotating space station i figured this would give a reasonable amount of movement between frames to increase the differences between frames i digitized it at only frames per second to give a total of frames i captured the raw footage at a resolution of pixels with the spigot card in my centris quarter size resolution from a pal source i then imported it into premiere and put it through the compact video compressor keeping the fps frame rate i created two versions of the movie one scaled to resolution the other at resolution i used the default quality setting in premiere and specified a key frame every ten frames i then ran the movie through the same raw speed test program i used for the results i d been reporting earlier result a playback rate of over frames per second that s right i was getting a much higher result than with that first short test movie just for fun i copied the movie to my external hard disk a quantum lp s and ran it from there this time the playback rate was only about frames per second obviously the mb internal hard disk also a quantum is a significant contributor to the speed of playback i modified my speed test program to allow the specification of optional scaling factors and tried playing back the movie scaled to size this time the playback speed was over fps clearly the poster who observed poor performance on scaled playback was seeing quicktime in action not i d try my tests with quicktime but i don t think it s entirely compatible with my centris and system unscaled the playback rate for the movie was over fps the other thing i tried was saving versions of the movie with preferred playback rates greater than and seeing how well they played from within movieplayer ie with quicktime s normal synchronized playback a preferred rate of fps didn t work too well the playback was very jerky compare this with the raw speed test which achieved fps with ease i can t believe that quicktime s synchronization code would add this much overhead i think the slowdown was coming from the mac system s task switching a preferred rate of fps seemed to work fine i couldn t see any evidence of stutter at fps i think i could see slight stutter but with four key frames every second it was hard to tell i guess i could try recreating the movies with a longer interval between the key frames to make the stutter more noticeable of course this will also improve the compression slightly which should speed up the playback performance even more lawrence d oliveiro fone computer services dept fax university of waikato electric mail ldo waikato ac nz hamilton new zealand s e gmt i m afraid i missed the start of this thread but there are three factors that can significantly affect quicktime s playback speed that you may want to take into account playback bit depth things are fastest when you play a movie back at the bit depth it was compressed for this is usually or bit but other depths are of course possible type of scaling qt is optimized for double size scaling other scaling factors hit peformance much harder playback window position movieplayer limits your window placement choices to advantagous pixel boundaries by default i m not sure about premiere any combination of those can radically alter playback performance image size is of course another biggie giving the movie player lots of ram can also make a real difference forgive me if these were mentioned earlier in the thread peter lee peter e lee software conductor specular international inc lee cs umass edu or h or w beauty is bits deep plus eight bits of alpha channel
