How to smart render a VBR in Vegas?

[schematic2]

Hi
Does anyone know how to smart render MPG's in vegas? I can get it to happen if its a CBR, but not if its a VBR source. Apparently you need to set the bitrate the same as the source, but how do you determine what the original is so Vegas is happy?


Thanks

[guns1inger]

Which version ? I know Vegas Pro 8 and earlier had no smart render for mpg.

If it only works when you set the bitrate the source then VBR will be out of the question.

[schematic2]

Hi guns1inger

Its Vegas 8 c. It works if you set the bitrate the same as the source especially if you rendered the file previously in Vegas. BUt how the heck can you tell what the exact VBR bitrate is on a file from a WINtv capture card? The whole point of this is I want to cut/join Mpegs in Vegas. I find the timeline hard to give up. Any ideas other than suffering with a less capable mpeg editor?

Thanks

[guns1inger]

VBR, by it's nature, does not have a fixed bitrate. The V stands for Variable.

My understanding of Vegas (which I have used for quite some years) is that up to and including Vegas 8, it expands Mpeg-2 video on the timeline, and always re-encodes. The only smart rendering it is capable of is unpressed DV source. I believe this changed in version 9 to some degree. I will give it a test when I get home, but in my experience mpeg-2 is always re-encoded in vegas.

I use Womble for all my DTV captures as I don't need fancy transitions, just a frame accurate cutter

[guns1inger]

OK. Home and having a read of the help files in Vegas 8.0c (build 260). The pertinent statement regarding Smart Rendering is this one :

MPEG-2 (for files such as those from HDV and DVD camcorders)

(My emphasis)

HDV encodes at a Constant BitRate (CBR) of 25Mb/s - the same data rate as DV. I don't use DVD camcorders, but I am guessing that Sony's cameras at least use CBR encoding as well. Which means that smart rendering is viable when using these sources. Digital broadcasts, for the most part, use VBR encoding, although usually within a fairly small range. Vegas cannot smart render these files because you cannot give it a matching bitrate - there isn't one. Vegas' smart render capabilities are built for people who shoot their own footage using specific cameras, not for just any old mpeg-2 clip you want to use.

So if you want all the bells and whistles of Vegas and you have VBR mpeg-2, you have to re-render everything.

If you just want to take the commercials out of digital broadcasts, there are several good cutters around that can smart render without a problem.

[schematic2]

Thanks guns1inger

Are you aware of any other semi-pro editors that smart render VBR, such as Ulead etc?

[edDV]

Thanks guns1inger

Are you aware of any other semi-pro editors that smart render VBR, such as Ulead etc?

Most MPEG camcorders encode CBR. VBR is done for didtribution. I'm not aware of any "smart render" editor that deals with VBR.

How would they? You may have a patent idea here.

[guns1inger]

Womble Mpeg Video Wizard and VideoRedo both handle VBR encoded material, but obviously they don't have all the features you are after. I seem to recall that some versions of VideoStudio could do this, but I don't know if they were also bound to CBR encoded material or not.

[edDV]

I guess I never considered VBR for "smart render" since I only used it for camcorder and TV captures*. That would mean each GOP has variable bit rate. A cut inside a GOP would need to be re-encoded to the same bit rate or a weighted average of the two cut GOPs.

Here is a detailed discussion of ULead Video Studio "Smart Render" and frame redundancy errors in pre version 9 that caused audio to go non-sync by two frames. In that discussion they say CBR and VBR produced the same result.
http://phpbb.ulead.com.tw/EN//viewtopic.php?t=3525&sid=a9c860163f385033c6753806b60239b2


* The TV captures were analog to Canopus ADVC-100, CBR DV-AVI that were "smart rendered (commercial deletion) in Video Studio and Vegas Pro (versions 8 and 9).

[edDV]

For what its worth, here is the Vegas Pro 9 Help statement on "Smart Rendering" (aka "No-recompress long GOP rendering"). Most of these camcorder formats are CBR but it does show support for XDCAM-EX VBR at 35 Mb/s average.

I've used it successfully for DV-AVI, DV-MXF and HDV.

There has been much forum chat about AVCHD smart render problems and that Sony is working on it.

[schematic2]

Thanks edDV and guns1inger.
I'll check to see if Vegas 8.c has that setting.....