AV asynchrony, smart render and the frame redundancy bug

jchunter · Post by **jchunter** » Sat May 07, 2005 5:40 pm

Alosada,
To be more clear, there are two basic tools for editing in Video Studio: (1) Save Trimmed Video and (2) Multi-Trim Video. STV renders a new video file while MTV just builds pointers to locations in a video file.

My question is about STV not MTV. Does STV actually produce redundant frames? (I don't know whether STV uses Smart Render or not...)
John

alosada · Post by **alosada** » Sat May 07, 2005 7:51 pm

Sorry about the confusion, John. In fact, I have very rarely used the STV function and, certainly, not for the past two years. As I said, I find it easier to edit my videos on the Storyboard.

Anyway, I have used the same mpeg file as in the multitrimming test to obtain individual clips with STV in VS8. As expected, all such clips contain a pair of redundant frames within the first GOP ─obviously, all except the one the beginning of which coincided with that of the untrimmed file because there was no backward reference frame preceding the first GOP.

In fact, the individual clips were all smart rendered (the preview screen did not change and the process was very fast).

Also, an mpeg file smart rendered from the trimmings was OOS from start to end and the lag grew after each splicing point.

In a similar test, VS9 introduced no redundant frames with STV and the composite mpeg was synchronous throughout.

Regards:
Antonio

jchunter · Post by **jchunter** » Sat May 07, 2005 9:43 pm

Antonio,
That is fascinating!

That means my new (current) project, which was edited completely within VS9, has all clean video clips and I should have no OOS problems when I burn the DVD even if I smart render the Project Video file. Right?

On a another subject: I have reported that every mpeg project that was edited in VS8 has serious Video File corruption when created in VS9 with Smart Render enabled. Now, we know that almost every STV clip in those VS8 projects has Redundant Frames. When these are Smart Rendered with the "new" VS9 code, could this be a cause for the video file corruption that I see?? (blockiness, stalling, extreme loss of A/V sync, flashbacks, aspect ratio faults, etc.)

John

sportswizdan · Post by **sportswizdan** » Sun May 08, 2005 7:22 am

Antonio...
Hi, I'm relatively new to this, so I just want to make sure I'm doing this right...so bear with me please. I'm using VS8. When I'm doing my editing I drag my clip from the library to the storyboard and use the scissors for my editing. When I'm all done with these clips, I go to "save as" and save my project file. There is NO SMART RENDER ath this time correct? I know that when i finally burn my final DVD that I turn off the smart render function, but I also should turn off smart render when burning my "create video file"? If I update to VS9 should I keep this process or smart render is OK with that version?

Thanks for your time, Dan

maddrummer3301 · Post by **maddrummer3301** » Sun May 08, 2005 5:00 pm

sportswizdan,

No, he's not saying that.
This thread is related to whenever you edit mpg2 files by cutting/splitting/merging
and other things.

If your capturing dv.avi then stay with dv.avi for all your editing and then when your
done (save the project frequently) goto Share -> create file and create your
mpg2 file. Make absolutely sure you are creating a "Dvd Compliant Video File".
DO NOT go directly to burning the dvd process without rendering your video first
to a mpeg2 video file onto the harddisk.
After you have done that check the mpg2 file to see if it plays correctly.

To create a DVD from the mpg2 dvd compliant file:
Start a NEW blank project.
Go directly to SHARE-> create Dvd.
Import the Mpg2 video file you created, make chapters, menu and burn etc.

Hope this helps,

MD

maddrummer3301 · Post by **maddrummer3301** » Sun May 08, 2005 5:03 pm

VS9 does have an OOS problem, not as bad as VS8.

MD

alosada · Post by **alosada** » Sun May 08, 2005 5:49 pm

Dan:

Smart render seems to be OK in VS9. At least, it doesn't produce redundant frames and their associated audio lag. In earlier VS versions, however, you mustn't use SR in the Create Video File step if you are to avoid the FR bug.

As regards project files, no rendering, whether smart or otherwise, is in fact involved in their saving —vsp files simply contain the information required by VideoStudio to know the changes you have made to your original file(s) in order to render the timeline contents when you tell it to.

John:

Provided the clips in your current project have gone through no smart rendering at any time outside VS9, your VOB(s) and DVD will contain no redundant frames or be subject to the resulting OOS.

I have so far had no problem rendering any old VS8 projects in VS9, whether SR was enabled or disabled.

Also, further testing has revealed that I may have underestimated the potential of STV all this time in favoring a timeline-based workflow. I have performed a few new tests with STV clips and obtained some interesting results which, if confirmed in replicate runs, may provide a different way of curing the AV asynchrony caused by redundant frames.

I hope I will be able to report on the confirmation tests tomorrow.

MD:

DO NOT go directly to burning the dvd process without rendering your video first to a mpeg2 video file onto the harddisk.

Skipping the Create Video File step introduces redundant frames and OOS in the resulting file if smart render is enabled, but so does smart rendering your timeline to an mpeg2 file, so there is no gain in this respect. Also, whichever way you choose, the OOS caused by the redundant frames will be repaired by the muxing engine —a proper version, obviously— at the Create Disc stage.

VS9 does have an OOS problem, not as bad as VS8

This sounds interesting. Could you please elaborate on it?

Antonio

maddrummer3301 · Post by **maddrummer3301** » Sun May 08, 2005 6:58 pm

Antonio,

I was giving that person the instructions for dv.avi process for creating
the mpg2 file, dv.avi to xxx.mpg
I saw one of his previous posts and he's capturing dv.avi type 1.

I haven't had enough time to test other files but I've encountered the same
audio lag as in VS8. The problem with testing is it takes so much time.
You must have spent weeks working on this problem and you are
truly respected.

As for me, I use smart-rendering. Why resample a 2 hour mpg file.
Takes to long, loss of quality. Best to stay with dv.avi if possible.
That's where VS really does a nice job working with dv.avi files.
Then export back to the camcorder or output to whatever you want.

But, sometimes we can't because the files are in mpg format such as from
a dvd recorder/camcorder. Not to mention the HD format that will force us
to re-render mpg files.

I used VS9 to edit and create the test mpg file. Burned it in another
application to create a dvd. It was out of sync.
I'll try burning a dvd folder using VS9 now and post back whether it's in
sync or not.
This only has happened when using Multi-Trim which is cutting into the
original mpg file and then rejoinging the 2 clips back together again.

MD

alosada · Post by **alosada** » Sun May 08, 2005 10:57 pm

Sorry, MD, I should have imagined you were trying to clarify something for him.

I've encountered the same audio lag as in VS8. The problem with testing is it takes so much time... I used VS9 to edit and create the test mpg file. Burned it in another application to create a dvd. It was out of sync. I'll try burning a dvd folder using VS9 now and post back whether it's in sync or not.

Please do and tell us about the outcome. In any case, I suspect the lag in your file is not due to RFs. Have you estimated how much audio your file loses in, say, one hour? Does the lag grow uniformly?

Why resample a 2 hour mpg file?

Yes, why? Had Ulead addressed the bug properly earlier, this topic would have been completely "redundant".

I know you and many others have got the message right, but please let me take this opportunity to emphasize something that I may not have made sufficiently clear for some people:

VS9 need not be, and probably isn't, completely bug-free as regards AV synchrony. It just doesn't seem to produce the audio lag that results from the redundant frames one gets when smart rendering an edited mpeg2 file in VS7 and VS8 ─which may have been the origin of quite a few OOS issues.

Thank you and all other posters again for your appreciation. I hope the time spent testing was worth the while.

sportswizdan · Post by **sportswizdan** » Sun May 08, 2005 11:05 pm

Thanks for the advice, but one more question please. Again i'm capturing dv-avi. after I'm done editing...when I go to my create video file...I was told that I should still create this as a AVI file as it is less likely to cause OOS problems. Then when I'm finally ready to burn that to a DVD, I then change the settings to Mpeg before burning...Is this correct?

Thanks, Dan

maddrummer3301 · Post by **maddrummer3301** » Mon May 09, 2005 1:51 am

alosada,

This time I started with a 9.6gig file and trimmed in down to
7 gigs. Did about 5 cuts (multi-trim).
Output to 1 single mpg2 file using smart-render.
Started the output at 3:11 and it completed at 3:25
That doesn't sound possible does it but that is the true time (14Minutes).

Then made dvd's using VS9 and Vegas software.

No audio sync problems playing back.

That's good news to me.

The other test I did I had trimmed the file down to about 4.3 gigs.
When I have time I'll trim the file down to about 3 gigs and see what
happens.

MD

maddrummer3301 · Post by **maddrummer3301** » Mon May 09, 2005 5:32 am

Dan,
Read my previous post and then the top sticky post on the VS forum.
The first top sticky post can save you alot of time. That's why it's there.

I would suggest to work with a 10-15 minute test video.
Capture from your camera as you do dv Type 1, NO editing at all.
Create a mpg2 file.
Exit & restart VS.
Goto burning module.
Import the mpg2 file.
Create chapters/menu
Burn the dvd.

Keep it simple at first and complete a 15 minute project.
Don't worry about "Smart Render".

Md

alosada · Post by **alosada** » Tue May 10, 2005 8:44 am

MD:

The time taken by VS to scan the clips on the timeline and smart render only the required changes can obviously vary widely depending on the combined length of the clips, the number and complexity of the edits and one's computer resources. I think 14 min is quite a reasonable time for a file 7 GB in size. For example, my 2.4 MHz P-IV system took about 17 min to smart render a file slightly less than 6 GB in size from one that was about 8.5 GB, but your CPU is probably faster and your HD may have been less fragmented than was mine at the time.

If Vegas produced a synchronous DVD for you, I can think of no reason for it not succeeding with the shorter file.

Anyway, simply checking whether VS smart renders properly does not require spending hours on a long project. Putting one of the VS avi sample files to the FR test will tell anybody whether or not VS does in a few minutes.

alosada · Post by **alosada** » Thu May 12, 2005 4:53 pm

OK, this is what I found in the tests involving the Save Trimmed Video (STV) function instead of multitrimming:

(1) Smart rendering 16 STV clips that contained two redundant frames each in VideoStudio 9 produced an mpeg file that retained the bad frames and was therefore OOS, the audio lag increasing at the start of each clip —after each pair of RFs to be precise.

(2) On the other hand, dumb rendering the STV clips in VS9 provided an mpeg file that was 30 frames shorter than the smart rendered one. The redundant frames were still there, but the number of audio frames now matched that of audio frames because VideoStudio had removed two video frames at the end of each clip. As a result, the composite file was “virtually” synchronous. And I say “virtually” because the lag introduced by the pair of RFs at the beginning of each individual clip (about 67 milliseconds in NTSC files and 80 ms in PAL files) was only offset at the end of the clip, when the surplus frames were removed; however, the asynchrony resurfaced only a few frames later when a new pair of RFs was encountered at the beginning of the following clip.

(3) Dumb rendering the STV clips in VS7 or VS8 provided the same results as in VS9.

The basic conclusion here is that projects consisting of STV clips can be converted into synchronous mpeg files at the expense of longer rendering times —smart render does not solve the problem— and of losing a couple of frames at the end of each clip. Alternatively, one can dumb render each STV clip separately and then smart render the composite file in VS9. This latter choice can save long rendering times at the expense of doubling the HD space required to store the mpeg files needed to burn one’s DVDs.

Also, simply inserting a long enough transition —1 second will normally suffice— between the STV clips before rendering the composite file —with SmartRender disabled— can help lessen the visual impact of the macropixels in the RFs or even completely conceal the bad frames if the second clip merged by the transition only starts to be displayed midway through it.

The foregoing doesn't apply to clips containing more than one pair of redundant frames (for example, because the parent clips were trimmed or applied a visual effect more than once). In fact, their asynchrony can only be cured in the Create Disc step —because all excess frames are removed at the tail of the clip, the audio lag they cause is only cancelled by VideoStudio, all at once, at the very end.

I have revised the “What causes the bug and what doesn’t?”, “Is there a cure?” and “How is the AV asynchrony repaired?” sections in posts 1 and 2 to reflect these results.

LGO · Post by **LGO** » Sat Aug 27, 2005 4:30 am

Okay, I've tried to follow this thread but I get lost quickly in the technical stuff.

I use VS 8 (w/o smart render) to output MPEG2 files to NTSC DVD specs. Everything's fine. No OOS problem. Plays in various players just fine.

I'm using a 3rd party DVD authoring tool and when I load my MPEG2 files I get the error message that there is an "open GOP" in the file." The message continues to say that I sould use my encoder to close the GOP.

How on earth can I close the file's GOP in VS8 when I output?

LGO

P.S. - Editing output is individual scenes in HUFFYUV AVI that are then made into a single MPEG2 at completion.