When to/not to Render to .avi?

PainterPaul wrote on 12/27/2003, 12:05 AM
After reading as mush as I can find here, I still need to ask under what particular circumstances does one render to .avi instead of rendering straight to mpeg2 from within Vegas. Apparently there are issues when it comes to projects with lots of fx, etc. But I can’t quite get a handle on it. If there are advantages to first rendering to .avi, please help me understand when/why. Also, if rendering to .avi, then how do I then encode to mpeg2 – pull the .avi back onto the Timeline, and re-render as mpeg2?

I will admit that I do not fully understand the advantages of Pre-Rendering. Does my above confusion stem from my lack of understanding when/why a Pre-Render is needed?

Thank you in advance.

Comments

kameronj wrote on 12/27/2003, 1:10 AM
Paul,

I'm not sure if my response is going to answer your questions of your confusion stemming from a lack of understanding of when/why a pre-render is needed.....because I'm reading three different issues in your question(s).

But here goes:

1. ...Under what circumstances do you render to 'avi' instead of 'mpeg2'.

You can render to AVI format anytime you want to. Uncompressed AVI takes up a lot of space on your HD. If you have tons of gigs free....render anything you want to AVI.

However, if you are going to subsequently take your footage and want to make a DVD, the DVD requires your files be MPEG2. You can render as MPEG2 before you make the DVD....or most authoring programs (worth messing with) will have some encoder and do the encoding when you go to make the DVD.

But regardless of where it is done - to make a DVD you have to render to MPEG2.

2. Issues with lots of FX, etc.

Regardless of the format you are rendering to....avi vs mpeg - if you have a lot of motion, fx, edits, etc, rendering your footage will take longer - and - depending on the bitrate you pick (as in lower quality) you could run into some issues with fx's and stuff....but under 'normal' circumstance, I wouldn't worry about it.

3. Is there an advantage to render to AVI first?

It depends on what you are using the video for. If you can work with uncompressed video - that is preferred. If you import an MPEG2 video in your timeline...work with it....and then render it to an MPEG - you are making a render of a render. This is going to take a long time and can cause quality loss.

4. If render to avi...how to encode to mpeg?

Yes....pull the avi back into timeline and render as MPEG2. Or you can use any other stand alone encoder and encode the AVI to MPEG2.

5. Pre-render?

Pre-render is what it sounds like...it "pre renders" the stuff you are working on during your entire edit process. It can save time in the end when it is time to finish the project. But you don't have to pre-render...you could just wait until all is ready and render you file....and go from there.

I'm sure others can (and will) post their thoughts also and some will be more technical and accurate. But I hope I can point you in a good direction.

farss wrote on 12/27/2003, 1:31 AM
Very good question. As is usual if it's hard to understand it's usually because there's no hard and fast rules.
If you're encoding from the timeline to mpeg then there's two processes happening. The encoder is requesting each frame from the app which serves them out to the encoder. Before it can do that it has to resolve all the FXs etc. If you only do the encode once then fine, but if after you've done the encode you realise the bit rate is too low or high then the whole process has to be repeated. Or say you also want a VHS copy, then for that it all has to get renderd out as well.

So my general preference is to render to a clean avi and work from that. Also I can PTT the rendered avi as a backup. A DVD is NOT a good backup, certainly that's all you need to make more DVDs but if you ever want to change anything on the DVD, good luck.

Also for anything over a few minutes I much prefer to break the project down into logical parts, render each part out and then bring the bits into a master project. You could even build your master project first, with just some text so you know which bits go where, gives you some idea of how long each segment will be and the order of them, sort of a top down approach. I like to also put all the assets for each segment its their own folder. That way if HD space does become a problem you can delete all the bits that made up that segment once it's complete.

Hope some of this helps.
Grazie wrote on 12/27/2003, 3:12 AM
These are my Rules:

1 - Do everything in AVI - uncompressed. Finish whole project THEN and only then go to another format. Reason: Changing backwards and forwards formats will, for me at least, drive me up the wall! PLUS, I would think that the time to render to avi and THEN to another format is most likley be less than allowing V4 to do the whole shtick in another format first. Oh yes! If you've done something that will required post render editing, far simpler and recommended to do this in full uncompressed AVI than in another format.

2 - Use Pre-rendered options for those complex effects. Reason: Recently I had a very complex patch in a video. Vegas got constipated and came back with a lot of error failures. I applied Pre-Rendereding and at the "patch" where I was having problems, it started to take a lot of time. So I can only think that at this place there was a lot of maths fgoing on and that the non-pre-rendered approach wasn't taking into account - don't know why - this large aount of rendering in a "smooooth" way. Anyways, pre-rendered problem solved!

Now these 2 rules mean you would have to have plenty of Real Estate to do this. I ecognised this when I first got into DV and budgetted for majorally large lumps of free hd. I buiolt up to 4 external firewire drives giving me a total of 340GB space. Now that I've got a dedicated pc, I use these external firwires inconjunction with a further 2x120 internal video drives - separate to the onboard 40gb system drive. This gives a total of 580GB for my video work!

Hope this "Real World" experience helps . . .

Grazie
jetdv wrote on 12/27/2003, 4:46 AM
Uncompressed AVI Grazie? What's wrong with DV-AVI?
craftech wrote on 12/27/2003, 4:51 AM
If you are using W98SE you will be limited to an Mpeg file size of 3.99GB. Vegas will not create multiple 4GB Mpeg 2 file sizes as it does with avi.
You will have to adjust the bitrate accordingly.

John
farss wrote on 12/27/2003, 5:35 AM
I agree,
if the stuff starts out compressed then making it uncompressed achieves nothing, the damage is already done. Given the quality of the VV codec even half a dozen recompressions shouldn't be noticeable and you'd have to be doing some wierd stuff to make that happen.
Let's not scare a newcomer into thinking he needs to blow the budget on huge amounts of disk storage.
Grazie wrote on 12/27/2003, 9:39 AM
Okay! Me bad . . DV-AVI . . not scaring anybody here! - Grazie
PainterPaul wrote on 12/27/2003, 10:42 AM
Thanks to all of you so very much!

Kameronj,

Before I got Vegas, I had a copy of Premier in which I dallied just a bit. As I recall, one had to “Pre-Render” in order to see the effects of fx . In Vegas, any applied fx are seen right away on the timeline. Maybe this is where my confusion started. And I should have made it more clear as to what my goals are. I render to mpeg2 for the purposes of burning DVDs (home movies – slideshows, etc.).

I have been reading so much here since finding the Forum, and I recall coming across various statements/situations where some have been rendering to .avi first. I was beginning to wonder why, and if I was omitting a step by rendering straight to mpg2, as I have been.

Also, I should have stated that I have been using DV AVI source, either directly from what I shoot on my Sony TRV-33, or transferred with it via PassThrough.

Farss,

Thank you for all the great advice! I appreciate this, especially re the backups.

I’m using Win2k with a 120 gig dedicated HD.

I realize that Vegas uses the source clips only to draw from during an encode, and that what is on the timeline is a scaled down version (something tangible to work with). I had planned on backing up some of my stuff (original clips -- analog transfers now nicely packaged in DV-AVI) by burning the clips themselves to DVD and saving the .VEG file/s. I can see that if I render a DV-AVI from within Vegas, or uncompressed .avi for that matter, all that source material is right there in a neat avi, but, if I have one large 13-plus gig file/s, how to get it off the HD?

>>Also I can PTT the rendered avi as a backup.

I don’t fully understand “PTT”. Chapter markers?

Grazie,

Ditto!

>>Oh yes! If you've done something that will required post render editing, far simpler and recommended to do this in full uncompressed AVI than in another format.

Your advice would still apply to my DV-AVI source (13 gigs per hour)?

Also, regarding Pre-Rendering. I understand your reasoning completely, and it makes sense to me. Question: All Pre-Rendering will be done in my source .avi format? Are these going to be separate files? In my case, DV-AVI because that’s what the source is? Then, I’d Render the whole project (with the bits of pre-rendered parts) into one whole .avi, and then, once satisfied with that, re-render the whole .avi to mpg2 for DVD burning.

Thanks everyone for the great advice and direction. Sorry about the additional questions! I just need to know I’m on the right track – like golf, you don’t want to start out with bad habits which will inevitably hold you back down the road.

Paul
PainterPaul wrote on 1/8/2004, 2:37 PM
Any replies would be appreciated.... Thanks!