VP80a SD MPEG smart-rendering

owlsroost wrote on 1/15/2008, 5:53 AM

As this question pops up periodically in other threads, I thought I'd post a topic re my experiences......

Vegas Pro 8.0a/8.0b **can** 'smart-render' ordinary SD MPEG-2. It's not an advertised feature but it does work - I've done several simple projects recently using the feature.

The tricky part is that you need to create a custom MPEG-2 render template which matches the parameters of the source files i.e. bitrate (the value in the MPEG headers), CBR or VBR, frame size, frame rate, field order and GOP length. Vegas can't give you all of this information so you need another utility to find this e.g. Bitrate Viewer [url=www.tecoltd.com/bitratev.htm]. The GOP length is probably best sorted out by trial and error - it's almost certainly 12 or 15.

When it's all set up correctly, you should see a 'No recompression required' (or similar) message in the preview window during rendering (other than at the edit points).

I've tried this with both CBR and VBR files from a DVD recorder and another hardware encoder with good results - the output files play OK, and Womble's GOP checker utility doesn't find any timecode/PTS errors etc - which certainly isn't the case with the smart-rendered output from the Ulead products I've used in the past......so well done Sony (Mainconcept?) for getting it right first time.

It's not as fast as Womble either for scrolling during editing or output file production (I've used Womble and MPEG-VCR for years) - but I've never seen anything else that comes close to Womble for MPEG editing speed so this isn't too surprising.....

What are other peoples experiences with VP80a non-HDV MPEG smart-rendering ?

Tony

Comments

DJPadre wrote on 1/15/2008, 6:54 AM

well i jsut did a "smart' render of HDV footage with some clips running colour correciton filters (levels actually) then moving back to untouched M2t, which theoretically should be smartrendred..

It was, and i wacked the disc into the PS3 as an M2t and lo and behold, the disc puked itslf when it hit that render stop/smartrender start point.

This is the 4th time happened with PS3..
On the Vegs timeline, the file seems fine.
On WM10, it also plays back fine...

m2t was rendered in V8, and burnt to DVD data disc using Nero

rs170a wrote on 1/15/2008, 7:11 AM

Tony, I can verify that what you say is correct.
I create a lot of custom templates for the SD renders I do so I can use them repeatedly.
I tried a re-render a few weeks ago, the preview screen said "no recompression jnecessary" and my machine flew through the render.

Mike

Rosebud wrote on 1/16/2008, 2:58 AM

Tony, thx for this trick!

I made some tests with mpeg from SDR150 panasonic camcorder and it works perfectly.
Unfortunately, I’m not lucky with mpeg from Sony DVD-Cam.
Have you tried with mpeg from Sony DVD-Cam ?

tia
Gilles

EDIT:

owlsroost wrote on 1/16/2008, 2:28 PM

well i jsut did a "smart' render of HDV footage with some clips running colour correciton filters (levels actually) then moving back to untouched M2t, which theoretically should be smartrendred..

Does it just stop playing or just break up briefly ?

Sounds to me like a problem with the PS3 (since it plays OK on the PC). I know that smart-rendering MPEG involves breaking up the 'normal' GOP structure (it usually creates a few short and/or closed GOP's around each join) but this shouldn't cause any problems for a properly implemented MPEG decoder, unless Vegas isn't doing it correctly.

I can't try it myself - I have an HDV camcorder but nothing other than a PC to play the HD files on as yet.

Tony

bsuratt wrote on 1/16/2008, 2:59 PM

Wolfgang S. wrote on 1/16/2008, 3:43 PM

Well, I can confirm that for PAL-SD material from a sat-receiver too (mpeg2 material written as PS to the hard disc, by a Hauppauge Sat receiver).

Settings are important - for my material it was
720x576
25 fps
PAR 4:3
I=12, B=2
main, main
UFF

constant date rate = 6000 ( seems to be the nominal data rate, as found with the bit rate viewer - can be changed with the DVDPatcher, as far as I have seen. But sometimes that seems to cause crashes too)

So yes, works fine here, using Vegas 8b.

And yes, it stays on constantly.

owlsroost wrote on 1/17/2008, 5:50 AM

When I render SD I get the "Render Not Required" message intermittently blinking which is unlike my experience with HDV where it stays on constantly, (except where changes were made). Is this normal or am I in the ball park but not right on target with all parameters?

It's probably the GOP length that's wrong (the 'I-frames' setting in the MainConcept encoder) - try setting it to 12 or 15 and see if that fixes it.

I DL'd BitRate Viewer but apparently need paid version to get all data needed. Teco website broke; will not allow a purchase at this time and they apparently have no email address.

If you haven't got the full version of BitrateViewer, then try....

To find the GOP length, load the file into VirtualDub-MPEG2 [url=http://home.comcast.net/~fcchandler/index.html]. Use the 'keyframe advance' buttons (bottom of the window) to step through the file while watching the frame count display (to the right of the buttons) - you should see it jump in 12 or 15 frame increments - this is the GOP length. There is a keyframe (I-frame) at the start of each GOP.

Tony

owlsroost wrote on 1/17/2008, 6:12 AM

seems to be the nominal data rate, as found with the bit rate viewer

Yes, it's the bitrate written into the MPEG headers that you need (not the actual stream bitrate) - this is the 'Nom. bitrate:' value from the information pane in Bitrate Viewer

This value should be used in the render settings as the 'constant bitrate' for CBR, and the 'Maximum' for VBR.

Tony

owlsroost wrote on 1/18/2008, 7:54 AM

Just had a play with VP80b.....

I looks like Sony have eased some of the 'matching' restrictions, so that you can smart-render a CBR stream to VBR output and vice-versa (provided the bitrate settings match), and also the GOP length setting can now be either the same or longer than the source GOP length.

(I notice that one of the bug fixes listed in 80b is for HDV smart-rendering, so presumably this has affected the SD MPEG behaviour too - for the better)

Tony

Laurence wrote on 1/18/2008, 2:31 PM

This is all really good news. Every so often I have to do some minor edit to a DVD: fix a mistake in the credits or something. Womble is cool, but it is missing some of the cool things you can do with Vegas, especially in matching titling looks, etc.

Zulqar-Cheema wrote on 2/6/2008, 8:59 AM

There some to be some variables in the no render required.

Recently I had to do some small edits on a project and having tried the above I thought it would be easy and quick.

I made a new track at the very top on the existing project and dropped the MPEG in (no audio as I use AC3)
made the alterations and then hit render and guess what , it was rendering the MPEG (titles & photos) up until normal the normal video appeared and then no rendering was required for some reason.

Deleted all tracks underneath the top track and still the same.
Open a new V8 and drop the same MPEG in and strangely or as expected, No rendering required.

Can anyone confirm anything similar or what this would be the case.

Thanks

bStro wrote on 2/6/2008, 9:36 AM

I'm a bit confused by your post. It sounds like you put an MPEG2 file into a project using three different methods, and each time Vegas was able to smart-render a new file.

So...what's the problem?

If you're wondering why you were able to do this without having to go through any finagling (as described in the above posts), I suspect that you just happened to be using an MPEG2 whose properties matched those of the MPEG2 template you were encoding with. If that original MPEG2 was created with Vegas, that's no surprise, since you probably used the same settings then as you're using now.

Or maybe I've completely misunderstood your post?

Rob

owlsroost wrote on 2/6/2008, 10:29 AM

That would be my take on what's happening too....

i.e. if there is nothing on part of the timeline which would affect the source video AND the MPEG render template matches the source video, VP8 will smart-render (basically copy across) that part of the source video unchanged to the output file.

Tony

Zulqar-Cheema wrote on 2/6/2008, 3:07 PM

Sorry I have not made myself clear.

In the existing project the with the MPEG file on the top TL it does a re-render for the first 2 minutes or so before going into no-re-compression required, even though there has been no changes or adjustment to the MPEG file at all

When I drop the same MPEG file in to a New (fresh) opened copy of V8 and render (as above) I get the No-re compression required straight from the start of the TL

SO basically in one project it decides to do a re-render for a about 2 minutes, while in another one it decides it does not need to.

Hope that clears things up a bit...

bStro wrote on 2/6/2008, 4:40 PM

It was this part from your post that threw me: "it was rendering the MPEG (titles & photos)...". I thought that meant you added something to the project there. If that's part of the original MPEG2, I'm not sure what happened. Sounds like a fluke. Can you do the exact same thing and see if it happens again?

Rob

bStro wrote on 2/6/2008, 6:16 PM

Just to show you the kind of flukes that can happen (assuming I did what I recall that I did ;), I created a 45 second MPEG2 using generated media. I used the NTSC DVD Architect video stream template for the original file and all subsequent files:

1. Same project, put the MPEG2 on a new video track above the others, rendered this out a new file. No compression needed. Expected.

2. New project, MPEG2 on only video track, rendered out to a new file. No compression needed. Expected.

3. New project, MPEG2 on only video track, cut off the last 15 seconds, rendered out to a new file. For the most part, no recompression needed, but I suspect that there was some brief recompression needed at the cut point.

4. Same as #3, but cut off the first 15 seconds instead of the last.

5. New project, MPEG2 only only video track, split into three events which I then rearranged. (Here's where the wierdness happened.) The first time I did this, the entire file was re-encoded. I closed that project and (as far as I know) took the exact same steps a second time, but this time no (major) recompression was needed.

Rob

Zulqar-Cheema wrote on 2/7/2008, 10:53 AM

Rob I can repeat the quirk, vene if I delet all the orginal tracks underneath with the footag eon it still renders the fisrt 2 minutes, but not if i open a new project

In your numbers above

1,mine renders first 2 minutes
2, no re-compresstion

Zulqar-Cheema wrote on 2/7/2008, 10:55 AM

Rob I can repeat the quirk, even if I delete all the original tracks underneath the MPEG it still renders the first 2 minutes, but not if i open a new project and place the MPEG in there

In your numbers above

1, Mine renders first 2 minutes, repeatable
2, no recompression. as expected

eh??

bStro wrote on 2/7/2008, 11:19 AM

Weird. If you want, you can send me the offending VEG file (none of the media, just the VEG), and I'll see if I can figure out what's happening during those first two minutes. Send it to bstro at 50mail dot com.

Rob

Zulqar-Cheema wrote on 2/8/2008, 4:30 AM

Veg file sent, 1070 kbs in size.

Thanks

bStro wrote on 2/8/2008, 9:29 AM

Got it. Sorry, couldn't figure out what might be happening, though. Only thing I can think of is maybe there's something different between the project properties of that VEG and those of a new project? Though I'd think that would have an effect on the entire video, not just the first couple minutes.

Rob

Zulqar-Cheema wrote on 2/9/2008, 2:12 AM

Thanks, what I will try is the above problem is in the quad core and the original project was cut on a single core machine, so may open in there and see if the effect is the same.

Zulqar-Cheema wrote on 2/9/2008, 2:12 AM

Thanks, what I will try is the above problem is in the quad core and the original project was cut on a single core machine, so may open in there and see if the effect is the same.

owlsroost wrote on 2/10/2008, 5:18 AM

Just tried the 'chopping an MPEG file into pieces and re-arranging' test - with either a new project or an existing one, VP8 always smart-renders the output....

So is Vegas caching something about the project when it shouldn't on some systems? I guess the safe thing to do is close and re-open the project before rendering.

Tony