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Skipping frames playing timeline or compressed videos - long post

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Skipping frames playing timeline or compressed videos - long post
on Feb 21, 2007 at 9:05:17 pm

The problem I am having is skip frames during playback in NLEs and skip frames during playback of compressed videos from those projects. I started noticing these skips in camera moves, zooms, pans and normal on screen motion.

It looks like the computer is sensing it's getting behind in screen update and just skips forward a frame or two to catch up.

Playback from the original tape of the same scenes, from the cameras to a reference video monitor, looks smooth. No visible errors on tape playback.

I am looking for an edit and/or compression solution that will eliminate the sticky/skipping playback in files that will be shown on or from a computer.

The system I am using now is FCP 5.1.2 on a G5 DP 2.0, Huge 1.8 TB RAID, AJA Kona LH. I shoot a JVC HD100 rev a, Ikegami Betacam and PD170. Footage from all three cameras (plus two other HD100s, an HD250, an HVX 200 and a DVX 100) skips in the viewer, canvas and full screen modes on my FCP system.

I have tested on several other Mac/FCP systems (G5 and Mac Pro), three Edius setups (AMD and Core Duo), two Vegas systems (Core Duo) and two Premier systems (AMD and Core Duo). All skip on these files and fresh captures from one or more of these cameras/sources. Dropped frame error messages were never presented.

But skipping on playback from the timeline in editing isn't really a big deal.

The big problem is that compressed files created on any of these systems embed the same skips, in about the same places, into the types of video files I need for my customers. MOV or WMV files for servers, LANS or CD/DVD data disks to drop on a computer for trade show playback to big screen.

The files that show the most obvious skips have been 720p30 from the JVCs and 1080i from the HVX.

To test edit/compression workflow for skips, I took locked down shots of freeway traffic and dropped the footage to each NLE, then made a web and LAN size video from the compression software suggested for that NLE.

I've tried Compressor 2.3, QuickTime Pro 7, Episode Pro, Pro Coder 2.0 and Sorenson Squeeze 4.5.

The constantly moving traffic makes skip frames easy to spot in real time playback. Testing for actual missing or duplicated frames with the cursor keys is easy with the even forward progress of each vehicle.

The skips show in every clip I shot, as all of the vehicles jumping forward about 1 frame. Skip frames happen repeatedly in about the same location on a clip, but not always the exact frame. Frame by frame advancing shows all frames are there, none missing. Each vehicle moves an equal distance as each frame is advanced. Skips will show at each effected location on most playbacks, but not every playback.

Apple engineering is looking into the problem and acknowledges it on the Mac Pros, but not the G5s (both look the same in all of my tests).

Apple sent an animation to check for skip/stick frames. So far, everything I have tested shows skip/stick frames on this animation also. It is a 720p30 Apple Intermediate Codec file, so it has to be transcoded to something that runs on any other system tested. AIC isn't in the codec set supplied with QT or Pro for Windows.

Edius engineering is looking into the problem too.

Every manufacturer I have talked to claims their edit and compression systems result in buttery smooth playback on computer monitors, flat panel TVs and projectors. All I have tried skip.

The following kernel of information is quoted from the Matrox MXO site -

"You can view your Apple Final Cut Pro projects ... as they will actually appear on TV and record them frame accurately to tape with perfect a/v sync

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