Slo-mo / resample problem (laggy blocks)

Cheesehole wrote on 3/22/2002, 9:10 PM
I have two systems, both with VV3. on one system, slow motion clips render to NTSC DV just as I expect them to. if I open the *same* project on the other system, and render from there, the resulting DV file has some strange visual artifacts.

I'm seeing what looks kind of like tape dropout, because it involves 'squares' or 'blocks' of video which appear to lag behind. it's only noticeable in sections of the video that are moving (the background doesn't move, therefore lagging areas of the background would not show up). it almost looks like when you search through a DV tape, and the video looks funny because the whole screen isn't updating at the same time.

the effect is obvious, and is easily reproducible on that system. I've tried rendering different samples of DV video. any footage rendered with slo-mo (either with velocity env or by adjusting the media playback rate) exhibits this problem. I'm rendering with resample checked.

it is important to note a few things I have discovered:

1 - rendering with the audio *unchecked* produces a clean video.
2 - rendering with resampling *unchecked* produces a clean video.
3 - playing the bad files on either system yields the same bad result.
4 - the actual video frames are intact, but when played in Vegas or Media Player, the file plays with the awful artifacts, indicating a problem with the *way* the file is encoded.

I know the frames are intact, because if I pause the video on a particularly bad spot, then move the Media player from one monitor to the other (effectively refreshing / re-initializing the current frame in the player), the frame refreshes to a 'clean' picture with no blocks. so it appears to be a problem with the way the file is compressed... not sure really.

I've posted an example frame here:
http://ben.orona.com/slomo/slowmocorrupt.jpg

I know people have had issues with slow motion, but has anyone seen this particular problem?

here are the system specs:
Dual PIII 450MHz
DFI MBoard
512MB RAM
SIIG 1394 using TI chipset

Comments

Control_Z wrote on 3/23/2002, 7:02 PM
I didn't see the blocks, just a kind of 'stuttering' on some clips. I tried everything for a day or two then gave up and have used P6 for slo-mo ever since.

Hope you find an answer before VV4!
Cheesehole wrote on 3/23/2002, 8:20 PM
yeah I definitely wouldn't describe it as being stuttery... it's really weird because I just re-installed everything from scratch on that system, and I thought that would fix it.

and when I render from my other system, the blocks are not present. I'm hoping someone from SoFo will have a suggestion.

- ben (cheesehole!)
SonyEPM wrote on 3/25/2002, 10:18 AM
Are you only seeing this in Media Player?
Are you also seeing this problem after printing back to DV and watching the footage on a TV?
Cheesehole wrote on 3/25/2002, 7:59 PM
>>>Are you only seeing this in Media Player?
No.
when played in Vegas or Media Player, the file plays with the awful artifacts, indicating a problem with the *way* the file is encoded.

>>>Are you also seeing this problem after printing back to DV and watching the footage on a TV?
Yes. I just verified that even after printing to tape the video plays on a TV with the problem. on a TV the effect looks more like when you play a tape in FF or REV mode. not as blocky as the screenshot I posted.

thanks for the response. I'm looking forward to fixing this. any idea as to why turning off the audio alleviates this problem? the re-sample switch seems to be at the heart of the matter since the only time this problem happens is when the resample switch is on.

resample ON + Audio ON = SCREWED UP CORRUPT VIDEO
resample ON + Audio OFF = NORMAL VIDEO
resample OFF + Audio ON = NORMAL VIDEO
resample OFF + Audio OFF = NORMAL VIDEO

should I send a sample of the file so you can look at the header info and all that jazz? is there a good way that I can do that on my own?

- ben (cheesehole!)

MORE INFO:
I've been doing more tests. I've discovered that the bad effect is extremely difficult to notice unless the background is NOT MOVING. if the background is static, the effect is obvious. the moving subject appears to have 'shearing' effects. it gets all split up into large blocks as it moves. (blocks of data from other frames appear at the wrong time and/or place)

the files do contain valid frames as I previously discovered by pausing media player and forcing a refresh (this can be accomplished by minimizing media player and then restoring it). they play back on my DSR-11 deck and other systems so they must be valid DV files, but they do not play back *correctly* on anything. to me it seems like that really narrows down the problem.
- what could cause a *compatible* DV file to play back with this 'laggy blocks' stuff?
- what could cause Vegas to render such a file?

guess I haven't tried deleting the whole Vegas folder structure and re-installing... I'll do that next.
Cheesehole wrote on 3/26/2002, 2:14 PM
>>>guess I haven't tried deleting the whole Vegas folder structure and re-installing... I'll do that next.

this is getting really bizzare.

that didn't fix it. I deleted the entire windows folder, program files, sonic foundry, documents and settings, (basically everything) and re-installed from scratch.

I'm *still* getting corrupt DV renders when using Resample with slow motion that won't play back right on any device.

- cheesehole :(
SonyEPM wrote on 3/26/2002, 2:28 PM
just curious- what video display card are you using on the good machine? bad machine?
Cheesehole wrote on 3/26/2002, 2:55 PM
>>>just curious- what video display card are you using on the good machine? bad machine?

GeForce2 MX in both machines.

the main difference is the OS
BAD machine = WinXP
GOOD machine = Win2k

both are running VV3.0a
drtelemark wrote on 3/27/2002, 1:27 PM
I had a similar problem with play back in DV mode (on tape). What I found, as you have eluded to, was having resample ON and having NO audio from the original recording being used gave me a clean slowmo when viewing it on tape. I still dub in music which has worked fine. Not sure if that helps you much but it cleaned my slowmos up quite nicely.

Interestingly, if using WMV format, all the slowmo stuff is perfect, when played on my PC.

My home built system doesn't hurt though - P4 1700mHz, GeForce3 card makes any playback pretty clean.