Render twice?

Cbrus wrote on 3/16/2006, 1:06 PM

I am a newbie, so please bear with me.
I created my first move with VMS and DVDA. It was a short 30 minute movie - basically it was youth hockey footage with the audio left attached to the video. I rendered it at mpeg2 in Vegas Movie Studio (took about 45 minutes). Then I opened this file in DVDA (that came bundled with VMS 6) and added 2 chapter markers - that's it. When I went to select "burn", it rendered again and took another 50 minutes. After that it burned the DVD, which was okay.

My question is, should it have re-rendered like that? Did I do something wrong? My guess is that every time a render happens a little bit of quality goes away - is this true?

Comments

DrLumen wrote on 3/16/2006, 6:29 PM

I'm not sure why but, yes, if you add chapter markers in DVDA it will render again. If you add the chapter markers in VMS, before the first render, You will only have to render it once. Make sure you have the "Save markers with file" checked in the settings for the first render.

Of course, this all depends on the finished size also. If your first render is larger than will fit on the disk, you will have to re-render in DVDA. There is a BitRate calculator on the web (sorry dont have the URL as I saved it locally) that will help you figure your bit rate for the first render. This will save another render cycle.

As to losing quality with each render, it depends on the format. If you re-render in MPG, yes it gets worse each time. If you rerender in AVI (DV), there is not much difference in each generation.

whr wrote on 3/17/2006, 9:04 AM

I realize it is a time hassle to re-render a video that you have already rendered but any time you make a change in the layout it will require a new render.

Just a side note: Sony Support told me a long time ago that when I render an edited video in Vegas I will get the best results by rendering to an AVI format and then let DVD-A re-render the video in MPEG2. It has helped the quality considerably and has actually made the re-render time faster since its not re-compressing an already compressed format.

ECB wrote on 3/17/2006, 1:16 PM

I am using Vegas 6 + DVDA3 so this may no apply but Ibelieve it does. If you mpeg encode in DVDMS or Vegas and import the mpeg 2 into DVDA, DVDA will not rerender the mpeg 2 when you add/edit the chapter points. DVDA will rebuild the VOBs but not rerender the mpegs. DVDA will rerender the mpeg 2 files if there are not compatable. What settings did you use when you encoded the mpegs in DVDMS?

Ed B

bStro wrote on 3/17/2006, 4:54 PM

I'm not sure why but, yes, if you add chapter markers in DVDA it will render again.

No, it won't. I have almost always set my chapters within DVDA. Have never had DVDA re-render anything that wasn't already DVD compliant. It prepares the project, but that doesn't take anywhere near as long as rendering, and it has to be done whether you add chapters or not.

Rob

DrLumen wrote on 3/17/2006, 6:25 PM

No, it won't. I have almost always set my chapters within DVDA. Have never had DVDA re-render anything that wasn't already DVD compliant. It prepares the project, but that doesn't take anywhere near as long as rendering, and it has to be done whether you add chapters or not.

I must have missed a setting somewhere then. I recently rendered a file in Vegas as an AVI. I then rendered it to MPG2 (create disk). After it rendered I went to burn and it wanted a marker in a particular spot for the layer split. I added the marker to the timeline in DVDA3 and it ended up doing a complete re-render. 11 hours worth (p1.8). If just a prepare, it took as long as a complete re-render.

s k r o o t a y p wrote on 3/17/2006, 7:19 PM

<<Of course, this all depends on the finished size also. If your first render is larger than will fit on the disk, you will have to re-render in DVDA. There is a BitRate calculator on the web (sorry dont have the URL as I saved it locally) that will help you figure your bit rate for the first render. This will save another render cycle.>>

~would you mind giving an example of how this works? i'm pretty new. i assumed that if your VMS timeclock says your project is under 60 mins. then it will fit on a 60 min. disc. is this not particularly the case? thanks.

DrLumen wrote on 3/17/2006, 9:24 PM

That's a good question. Seems like it should fit huh? I haven't run all the possible numbers but I think it is conceivable that you could have 1 hr of video that would be over the size limit. Others here could probably answer your q exactly. This may depend on how strictly DVDA, your DVD media and burner adhere to the "standards". IMS, I think (not sure about the exact numbers) that MPG2 will support 15mbps transfer rates but the DVD standard is about 9.8. If encoded at 15mbps you would not be able to get an hour of video on the disk - if DVDA does not limit the xfer rate.

Here is the link to the bitrate calc. As you will see, this works backwards taking your DVD capacity and then tells you what your max bitrate should be.

However, if you edit and encode to AVI from VMS and then just "Fit to disk" in DVDA for your DVD size, it will fit regardless of the content. This is what I like to use. There are cons to using this method but, for me, the advantages aren't worth the extra time and hassle.

s k r o o t a y p wrote on 3/19/2006, 6:33 PM

~yeah, i was wondering about those cons you mention. i started a new thread (optimizing bitrate: what's effected?) and would appreciate your insights. thanks.

Cbrus wrote on 3/19/2006, 7:44 PM

Thanks Everyone for the advice. I will check my settings and see what happened. From what I recall, I simply brought into DVDA an MPEG2 file that was rendered in VMS. I added 2 chapters and selected the "burn" option. At this point a screen popped up with three phases: render - prepare- burn. It spent approx 45 minutes on render portion, and less than 10 on prepare and burn. It was 30 minutes worth of video. I'll check all of this and post info this week.

Chris

s k r o o t a y p wrote on 3/19/2006, 8:42 PM

~at what point do you decide whether your project goes to DVDA as AVI or MPEG2? because you always edit in AVI and never MPEG, right? and i would think it stays that way unless you specifically opt to change it to MPEG2 at some point? i don't remember seeing MPEG2 offered to me in the prompts toward render in VMS.

kitekrazy wrote on 3/27/2006, 4:35 PM

"Just a side note: Sony Support told me a long time ago that when I render an edited video in Vegas I will get the best results by rendering to an AVI format and then let DVD-A re-render the video in MPEG2. It has helped the quality considerably and has actually made the re-render time faster since its not re-compressing an already compressed format."

I did that and 4gb of mpg files turned into a 20gb AVI and then sent it too DVDAS and when it was burnt to a DVD the video quality was horrible.
I'm starting with vob files to begin with.

bStro wrote on 3/27/2006, 6:19 PM

Sony support was referring to leaving your footage as AVI (if that was its original state) and bringing it into DVDA. Going from MPEG (including VOB) to AVI and back to MPEG is pretty much always going to give you lousy quality. If you're starting with MPEG (including VOB), you're best off staying with that format all the way through. Though you wouldn't want to edit it in Vegas... You should use something that does MPEG2 smart rendering (for example, TMPGEnc MPEG Editor or Womble's MPEG Video Wizard).

Rob