Please school me on Proxies

goodtimej wrote on 3/18/2008, 12:07 AM
I am getting ready to edit a boatload of HD footage and I was thinking maybe a little help along the way for my processors might be nice.
I hear of this thing called proxies and I know nothing of them. I have done a little research but can't quite get a definitive idea nailed down of what they are and if I have access to them with Vegas Pro. Can someone give me the lowdown please? Benefits and drawbacks? Thanks

Comments

farss wrote on 3/18/2008, 1:24 AM
A proxy is just a copy of the full res media, anything that's easier to edit. Once you finish the edit you can then swap the full res files for the proxies and render. Or say it was 35mm film. You get DV proxies, edit them, send the EDL off to a high end facility and they take it from there working with the full res images. Saves you paying a fortune while you ponder the cuts.
Advantages are fairly obvious.
Disadvantages. You don't get to see the images in all their glory while you edit. You need to make very certain that you can precisely match your proxy to the full res master. A not uncommon error comes from film being 24fps and video 23.976. Don't sound much but by the end of a feature it's quite a few frames.

Other disadvantage. With HDV you need to capture the HDV material as such and make the proxies from that so you've got to have double the amount of media on your drive(s). Gearshift from VASST seems to be the best solution. Keep in mind that you really can only edit proxies, you don't use them to make color correction decisions. That sort of means being a bit organised. Edit, lock edit, switch to full res, grade. Gearshift I think will let you switch on the fly so you can grade as you go I believe.

In general with faster CPUs and systems it's less of a common way to work. I think Avid really built their reputation on this kind of workflow. For example you can capture DigiBetacam as DV using a cheap J30 VCR. Edit that on any laptop and then send the project and the tapes to a high end Avid suite for the final grade and render.

Sorry if my explaination wandererd a bit. It is a pretty broad subject. Perhaps if you have some specific concerns I or others can answer them better.

Bob.
NickHope wrote on 3/18/2008, 2:02 AM
A couple of further things to supplement Bob's excellent explanation:

Rosebud's free Proxy Stream script can also handle proxies.

You can use MJPEG proxies instead of DV or whatever.
riredale wrote on 3/18/2008, 10:25 AM
I use 'em all the time. GearShift is your friend.

My dual-processor PC can play HDV files just fine, but when my project gets loaded up with multiple tracks, color correction, transitions and such, the preview frame rate bogs down. With DV, however, the action is much snappier, and it's effortless to GearShift back to the original HDV clips when it comes time to render to DVD or back to tape. Only real downside, as mentioned, is that there is an extra step involved--you need to render the proxies in the first place. But that's a trivial matter for me; after pulling in all the m2t originals, just set up GearShift to render them all into avi equivalents overnight.

By the way, the proxy rendering goes faster if you tell Vegas ahead of time to not show timeline frames and audio waveforms. But you'll have to render those objects, too, eventually, so perhaps it makes sense to have them done at the same time (overnight, when you're dreaming of accepting your award at the Cannes Film Festival).
goodtimej wrote on 3/18/2008, 11:55 AM
Couple of follow questions here.
Can I batch render the proxy files?
Is there a pretty good difference in playback FPS if you go proxy?
How much space do the proxy files take up?

Lets suppose we are talking about Gearshift here from HD footage. Thanks.
Kennymusicman wrote on 3/18/2008, 12:50 PM
1) Gearshift takes care of that
2) It can make a huge difference! The proxy can be as high or low quality as you like. So you can edit your "HD" footage using a tiny rate/quality proxy at full speed
3) depends on the type of proxy. A proxy is any format you choose. If you choose a HD proxy - it'll be big. Choose the smallest proxyt in the world, and it'll be tiny
NickHope wrote on 3/18/2008, 1:28 PM
If you are talking about DV proxies for HDV footage then the proxies actually take up a similar amount of space as the HDV because of the compression in HDV.

MJPEG proxies would take up less than DV.
Cliff Etzel wrote on 3/18/2008, 3:19 PM
Nick - What has been your experience working with the mjpeg proxies? I wouldn't mind having smaller sized proxies to work with while editing - especially on my single core laptop with external drives.

How do you get them to integrate with Gearshift???

Edit: Had to translate the page that was noted and am testing right now to see how this fares with the standard Gearshift Proxies.

Cliff Etzel - Solo Video Journalist
bluprojekt | ImmersiveVJ.com
goodtimej wrote on 3/18/2008, 3:21 PM
More troubleshooting if you care to bear with me:
I take a basic .m2t file that is about a minute and a half long and simply drag it onto a blank timeline. HDV 1080-60i footage and project. When I play back, if the preview window is not resized and I choose Preview Auto, I get about 13-14 frames per second. Good Auto takes me to 10. This seemks kind of jerky and slow to me and I am sure will be halved when I start adding titles to the mix. How many frames a second do you usually shoot for when you edit?
Kennymusicman wrote on 3/18/2008, 5:09 PM
Depends. For example, lets say an 'edit' was actually just a color correction - realtime is not much of an issue then. Now lets say I have a wipe transition, that is being sync'd to an audio track - to judge it I need to be able to monitor in realtime - otherwise the purpose is defeated.

Also - image having your preview window on a second screen, set to a large resolution (for example, I'm at 1920x1200) and having that playing your edits in realtime. A couple of HD clips and effects - not happening. Quick change into proxy - yes my resolution is temporarily reduced, but everything is big, clear and smooth and @ realtime...
farss wrote on 3/18/2008, 6:05 PM
Ideally when editing you want full frame rate playback, you really cannot judge an edit without that. If you've got a client looking oh boy, you do not want jerky playback or audio wandering out of sync like I get.

The problem with HDV and all long GOP mpeg-2 codecs is the overhead in decoding. Changing the preview res in Vegas does little to nothing to improve the playback rate of a single track with no FX. The decode overhead is fixed. Transcoding to a wavelet codec such as Cineform gets around this problem. A low res version of the frames can be decoded very easily so you pretty much have a built in proxy. Unfortunately from what I can see Vegas doesn't avail itself of this capability with the wavelet codecs.

Bob.
NickHope wrote on 3/18/2008, 10:33 PM
Cliff i haven't actually done it. I got the idea from Laurence. Where possible I edit on my Q6600 without proxies now. Where I used proxies a lot was by capturing downsampled DV on the boat straight from my Z1, then capturing again in HDV later for my archiving. By getting the names to be compatible (a bit of trickery using Sclive, HDVSplit and Bulk Rename Utitlity) this worked well as a proxy workflow. However recently I have noticed the difference in clip length between the DV and HDV captures. Now I've ordered a much faster laptop and am hoping to avoid proxied altogether and just use m2t..

Regarding fps for editing... when I'm cutting clips together I hate having anything but real time preview to judge the edit points.
riredale wrote on 3/19/2008, 9:47 AM
Goodtimej:

I've tried a couple of different proxy types, but generally use DV in that capacity.

The data rate for m2t files runs about 12GB/hr. Curiously, the data rate for DV is actually a bit higher, at about 13GB/hr. So using proxies in this manner pretty much doubles disk space requirements, but no big deal in an era where a 500GB drive is just $99.. In the past I would render to MPEG2 (for DVD authoring) from a DV file, but discovered that this just killed horizontal color resolution for certain colors, red particularly. So now I edit in DV but then GearShift back to m2t before rendering to MPEG2.
JohnnyRoy wrote on 3/19/2008, 2:42 PM
> How do you get them to integrate with Gearshift???

This is documented in the GearShift User's Guide on page 12 under Creating your own Proxy templates:

You can create your own proxy templates and GearShift will show them in the dropdown selection box. To do this save your proxy template so that the first four characters are "GSP " (that’s ‘G’, ‘S’,‘P’, ‘<space>’) Any AVI rendering template that begins with "GSP " will automatically be shown the DV Proxy dropdown. You can also make new intermediary templates by prefixing your template name with "HDV ". This allows you to customize the quality of any of your templates.

Obviously it has to be a template that uses a codec that Vegas can work with.

~jr
goodtimej wrote on 3/19/2008, 9:11 PM
So when you say edit with DV, do you mean uncompressed .avi 720x480, but still on the HDV timeline?
riredale wrote on 3/19/2008, 9:56 PM
"DV" as in the official DV Video standard, 720x480, running at about 4MB/sec. DV is not uncompressed; it uses a type of compression very similar to jpeg and is compressed about 5x what "raw" uncompressed video would be. It's easier for computers to handle than 1440x1080 m2t files, which use more complicated technology to effect a much higher compression rate.