[ This article was first published in the November, 2008, issue of
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Rich Roddman, of CMR Studios, writes:
I have been doing a lot of web video that the is shot on green screen. I bring the files into Final Cut as Pro Res media @ 1920 x 1080. My final output will be 640 x 480. (I use the 1080 so I can adjust the size for wide shot to close ups and anywhere in between as needed) If I have my master timeline (Square pixels & Progressive) at 720 x 480 I can playback with an orange bar, but if I make the timeline 640 x 480 in get a red line and need to render to see anything. I don’t understand why the aspect ratio set at NTSC (4:3) causes a full render to be needed but NTSC DV (3:2) can playback?
Larry replies: Rich, my guess is that this is because 720 x 480 is a video format designed for real-time playback inside Final Cut, while 640 x 480 is a video format designed for the web that can be played back only after compression is complete.
MORE PLAYBACK PROBLEMS
Derek Casari, of Fox Post, writes:
My question involves 1920 x 1080 resolutions. I had a couple of test clips made for me:
Here’s the deal. Only one file played back without motion artifacts when imported into just ProTools. That was the Apple Photo JPG at 170 mb/s. The other Apple Photo JPG at the higher data rate and the H.264 both showed artifacts. All of these were 24 fps and 1920 x 1080. I’m thinking that the data rates are the issue and maybe I’ll just have to empirically create a number of files to find one that plays back without problems, which seem to be temporal aliasing. BTW, is Apple Photo JPGA different than regular photo JPGA? I’m trying to avoid the GOP codecs because of the issues they have with sync and frame boundaries. Any suggestions on a codec AND data rate for playback of a QT movie imported into Protools at 1920 x 1080 would be a big help.
Larry replies: Derek, it depends upon how your video was shot.
Motion JPEG-A is designed to work with interlaced footage.
Photo-JPEG is designed to work with progressive images.
Both have a reasonably small data-rate, yet are easy to uncompress without taxing the playback system. This is critical because you want your computer to spend its time running ProTools, not in decoding compressed video.
H.264 uses GOP compression and requires serious computer horse-power to decode.
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