video bogs down when scanning clips in browser

Just loaded 10.1.1 and anything faster than 2x speed and the video skips then freezes so I can't see where I am. Got 8 gigs memory.... Ideas? Thanks!

What Mac model and year do you have?

What format is the media? (i.e. h264, optimized, proxy, etc.)

When you say anything faster than twice the speed, how are you playing back that fast? Are you skimming, or using the JKL transport controls?

It's a 2009 Macbook Pro 2.8 GHz Intel Core Duo, OS 10.9.3; optimized media. I'm using JKL. Thanks.

That is a tuff one.

At some point any machine is going to run into disk speed issues. If you think about optimized 1080 video (16.5 mb/sec), to play 2x speed you double data data rate (now about 32MB/sec), and pressing L one more time will double it again to 4x, which is now 4 times the data rate (now about 64MB/sec). That is unless I wrong about how playing back a faster speed works. So if you are working off an external firewire drive you are lucky to get over 50MB/sec sustained, the internal HDD drive might not even be that fast.

Add to this that your specific Mac, the 2009 MacBook Pro has a GeForce 9600M which is not the strongest performer with OpenCL and therefore FCPX. So that is also a factor.

There is some good news however. Proxy is just what the doctor ordered. Why don't you try transcoding a few clips to proxy (File > Transcode Media), and then switch to proxy and see how you like that.

Good advice...

tpayton wrote: ....pressing L one more time will double it again to 4x, which is now 4 times the data rate (now about 64MB/sec). That is unless I wrong about how playing back a faster speed works. So if you are working off an external firewire drive you are lucky to get over 50MB/sec sustained, the internal HDD drive might not even be that fast....try transcoding a few clips to proxy (File > Transcode Media), and then switch to proxy and see how you like that.

My tests show this is how I/O rates scale upward in progressively faster playback of optimized HD media, at least to a point (all values approx):

Speed - I/O rate - Elapsed playback time
1x: 16.5 MB/sec - 91 sec
2x: 33 MB/sec - 45 sec
4x: 65 MB/sec - 23 sec
8x: 112 MB/sec - 11.2 sec
16x: 120 MB/sec - 5.7 sec
32x: 125 MB/sec - 2.7 sec

The actual playback time decreases linearly as expected, to the maximum rate of 32x. The I/O rate increases linearly to 8x, then it flattens out. There is apparently some optimization applied at this point, which only makes sense. When skimming at very high speed, FCP obviously doesn't do sequential reads at that rate.

On my 2013 iMac, I didn't see any difference in I/O rate or FF playback performance when toggling the viewer display options between "Better Quality" vs "Better Performance". However on a slower machine it makes sense to ensure it's set to "Better Performance".

A possible workaround is just skim to the desired timeline point and Option-click to position the playhead there.

Config details:

2013 iMac 27, i7@3.5Ghz, 32MB, GTX-780M, 3TB Fusion Drive, Media: Thunderbolt 8TB Pegasus R4 RAID5, OS X 10.9.3, FCP X 10.1.1, media: 1080p/29.97 optimized from Nikon D800 MPEG-4 .mov file.