CFHD and frozen frames

farss wrote on 2/11/2005, 12:42 AM
Did some more testing today, made DVDs from HDV source goin down differeing paths but I'll save that for another time. Each time I was working from a CFHD DI created from a m2t stream captured using the CF utility. Now at various points in the created DVD we were notcing frozen frames. Well I'd sort of expected them but this was a new Z1 and new stock but only the standard Sony fare. What got me thinking was there was more of these problems than I'd been led to believe there should have been.

So I put the CFHD avi and the m2t file on the 1 T/L and after some difficulty syncing them up found the offending part in the CFHD AVI file. Muted the track and shock, horror! The m2t file is PERFECT.

I gotta ask what gives, I have 10 identical frames in the CFHD avi file and perfect motion in the m2t file!!..

Now before anyone jumps to the wrong conclusion please take note:
The m2t file was captured to disk from tape. The CFHD files was created from the m2t file on the HD at Maximum File Size using the CFHD utility. My only conclusion is that there's something in the m2t file that the CFHD encoder couldn't handle. I encoded the offending section to mpeg-2 from the m2t file and it's perfect, the same cannot be said coming from the CFHD DI to mpeg-2 and hence DVD.

Bob.

Comments

farss wrote on 2/11/2005, 1:38 PM
Shameless Bump!
If there's anyone out there using Cinframe HD that thinks they've had a tape dropout, can I ask you to check the m2t file and see if the same 'dropout' is there as well.
Bob.
Spot|DSE wrote on 2/11/2005, 1:40 PM
Farss, I forwarded part of your mail to David Newman, and also sent him this link. I hope to hear back from him soon.
farss wrote on 2/11/2005, 1:48 PM
SPOT,
thanks so much for your efforts on this one. I'm kind of hoping though that someone else could also check this out to see if they're seeing the same thing. I'd hate to have CF go off on a wild goose chase.
Bob.
epirb wrote on 2/11/2005, 2:17 PM
Bob
now long were the clips where you got the frozen frames, I'll try it to but just wondering if they were fairly short m2t files that you converted to the CFHD or long ones (+30mins)
If I'm correct you yau said the m2t fielare fine then you converted then to the CFHD avi from the HD yes?
I dont believe we have the choice as to where to output the avi ie another folder or drive.
Just wanna compare apples to apples.
farss wrote on 2/11/2005, 2:28 PM
Video is 42 minutes in one take.
Captured as m2t with CFHD utility then converted to CFHD avi after capture at Maximum File size.
All I'm suggesting is if you see what looks like a tape dropout (a sequence of frozen frames) when working from a CF DI then go back to the m2t file and see if it's there as well. I know the m2t files are very hard to deal with. What I did once I'd found the place in the CF DI on the T/l was to add the m2t file on another track.
One odd thing I did note doing this, the files do not lineup exactly, once offset to get them in sync though they're visually identical (apart from the frozen frames).
Bob.
Spot|DSE wrote on 2/11/2005, 2:45 PM
Most of mine are 60 min caps, as the non-production M10U I've got doesn't manage scene detection well. But I've compared both, mostly as a speed test thing, and haven't seen this.
farss wrote on 2/11/2005, 3:27 PM
So OK, are you saying you can find frozen frames in the DI and there's matching frozen frames in the m2t file?

This footage is a real stress test of everything, optics and encoders!
For a lot of it at least 30% of the frame is black, gain is way up as well, we shot one act at +18dB.

Even coming off the the m2t file straight to mpeg-2 for DVD the players are having difficulty playing the resulting DVD, I suspect the bit rate is going through the roof due to the noise and level of detail. I didn't have the bitrate analyser on the PC to check this out, will do that in next few days and report back.

One thing I've noticed with HDV, noise is much harder to see compared to DV, at first we thought wow, this is noise free. Then we zoomed in and wound the gain up in Vegas and there's heaps of chroma noise. Visually it's not there but obviously the encoders see it.

If need be I can snail mail files on a DL DVD for someone to look at (at last a use for D/L DVDs). I think the source is under 8.5 GB but the resulting AVI is HUGE!

BTW, did I see a post somewhere about a bug in the Vegas GB FX and HDV, it seems to be applying WAY more blur than it should. I know it works fine on 1080i HD.

Bob.
Spot|DSE wrote on 2/11/2005, 4:13 PM
No, what I'm saying is I'm matching the avi to the transport stream and NOT seeing the mismatched extra frames. They line up in length perfectly. Are you shooting CF24, CF25, CF30, by chance?
farss wrote on 2/11/2005, 4:23 PM
Shooting 50i
These are NOT mismatched frames! I did have some difficulty lining up the two files on the T/L but let's ignore that issue for the minute.

I can find a segment in the DI where I have 10 identical frames. The same 10 frames in the m2t file have perfect motion. The frames before and after those frozen frames line up perfectly and are visually identical, notion before and after is 100% correct.

In other words in the DI it looks like a classic HDV tape dropout yet it's not in the m2t file from the camera.


Bob.
PeterWright wrote on 2/19/2005, 5:33 AM
Things get buried quickly these days, Bob ....

How are you going with the frozen frame problem?
farss wrote on 2/19/2005, 6:04 AM
Thanks for asking, I'm amazed it didn't raise more interest. Tape dropouts get regular mention as a big mark against HDV yet perhaps from what I saw they may not be dropouts on the tape that people are seeing or there's some minor glitch on the tape that throws the CF encoder off.
So I've just left it for a while, I should go back and try the transcode again and see what I get.
I grabbed a spare FX1 today and shoot some footage of my own, cars going past on the freeway and the good old Opera House, thankfully I had the trusty Miller Solo as well so rigging it by myslef was easy and the Solo is very easy to setup over ledges as it doesn't have a spreader.
Anyways so far the footage looks great, I had the camera in manual exposure and watched the zebras so I was only just hitting 100, I've a suspicion the camera tends to overexpose a bit for Australian conditions with such a hard light, the sails on the Opera House on a bright day are a challenge.
I did notice I was getting chromatic abberation on sharp white to black transitions on things like boats, guess that's the optics! Also tried a range of shutter speeds, don't quite know what that was doing for me (or not).

I need to run some more tests but I'm certain Vegas isn't always handling the CF DI properly, rendering down to DV25 PAL looks great, going straight to mpeg-2 looks really bad, going to Sony YUV looks bad, going to WMV 9 720p looks awesome as does WMV 9 1080p but I'm having odd problems playing that. Biggest issue is my HP monitor is only JUST big enough for 1080 so trying to avoid having things rescaled is problematic. I've also noticed even in the WMV 9 720p footage some interlace aliasing, I got rid of it with the trusty Reduce Interlace Flicker switch on the source. Sure wish Sony would fix this issue, it's thru everything.

Anyway it's a bit of fun, fortunately I get to play with the cameras for free!
If anyones interested uStuff have a rather nice Robotica WMV HD logo I guess we're all free to use on the front of our WMV HD stuff.

And while you're on the uStuff HD site, download the trailer for Dust to Glory, I'm told it was shot on HDV, if that's the case they're having many of the issues I'm seeing as well.

Bob.
PeterWright wrote on 2/19/2005, 6:25 AM
Bob, thanks for all that - please keep posting your experiences - I'm like a piece of blotting paper ("what's blotting paper?") with anything related to the Z1 - I'm still waiting for mine. Things move slow out West ....... the good news is, when the world ends, it'll be days before we hear about it.
farss wrote on 2/19/2005, 6:38 AM
We've got 2xFX1s, 2xZ1s and three decks.
I'll put good money on Sony bringing out a new deck that'll take a D5 shell, the cutouts are already in there for it. They don't even try to hide the fact that it's the same transport as the camera either, the menus look the same, probably even the same LCD screen.
Bob.
epirb wrote on 2/19/2005, 2:06 PM
Bob ,
just an update on my end,nothing real conclusive yet but I capture some footage that I shot the other day and found a black frame in the CF DI ,like you I placed the m2t file below it matched it up, no black or dropped frames.
This aslo happed to be in a clip where I was shooting 60i then switched to a profile with cineframe 30. dont know if that has anything to do with it, but Im gonna check the rest of the clips that were shot at the same time in std 60i.

I also tried to reconvert the m2t file with HDLINK , the black frame appears at the exact frame as the previous encode.
farss wrote on 2/19/2005, 2:23 PM
Well it sounds like I'm not alone with these problems. Haven't had any black frames, just duplicated ones, around 10 in a row in one place.
I guess we cannot expect the Vegas guys to take much interest in this as it's all CF code that's doing it, hm, might try talking to them.

Bob.
farss wrote on 2/20/2005, 10:40 PM
Just an update, converted all the footage I'd shot on the weekend and yip, still more sequences of frozen frames and now that I know what else to look for I'm seeing the odd black frame as well (thank you epirb).
Someone did mention that there's a newer version of CF HD on the CF site. I guess as my 15 day free trial is about to expire I can buy it for $149 from here and then upgrade for free from the CF site.
Bob.
David Newman wrote on 2/21/2005, 9:30 AM
" I guess as my 15 day free trial is about to expire I can buy it for $149 from here and then upgrade for free from the CF site."

The versions distributed by Sony and CineForm are slightly different. The Sony version uses the same MPEG2 decoder that ships with Vegas. The CineForm version has licensed another MPEG2 which we find is faster, that is why there is a price difference. Black frames or paused frames would be a failure of the MPEG decoder to delivery frames to the CineForm encoder (it is not an encoder issue.) So I would like to know which version of Connect HD (Sony or CineForm) you are using, so that we can know which MPEG2 component is at fault.

Note: When ever you do find a repeatable fault, please report a trouble ticket on the CineForm website. This is the fastest why to get issues addressed.
farss wrote on 2/21/2005, 1:37 PM
Dan,
thanks for taking the time to reply.
I'm using the version from the Sony web site.
Certainly if there's a difference in what we get from the two sites this seems to be the first time that's been explained. I was under the impression that Sony had done a deal to bring your product to Vegas users at a discount as they'd be the ones handling any technical issues hence I raised the issue here.

Just as a passing note though, it would seem that the 'Vegas' mpeg decoder can correctly decode the frames, at least in some form. Lining the avi and m2t file up on the timeline so they're frame accurate the avi has a sequence of frozen frames but the m2t file doesn't. I'm assuming that to display the m2t file Vegas is using the same decoder as is used to pass the frames to your encoder.

Bob.
David Newman wrote on 2/21/2005, 3:46 PM
" I'm assuming that to display the m2t file Vegas is using the same decoder as is used to pass the frames to your encoder."

The calling mechanism is different, and the settings for MPEG error handling may be different. If you have a short M2T sequence that always converts with this error, could you send that to CineForm? Thank you helping narrow this down.

David.
farss wrote on 2/22/2005, 12:34 AM
Unfortunately it's in a 40 minute clip.
I'll see if I can find another instance in something more manageable.
I'd just render out that piece but I'm suspecting in the process I might alter the issue. I'll run some more test tomorrow.
Bob.
PeterWright wrote on 2/22/2005, 12:54 AM
Bob - IF a frozen frame was consistent with a particular section of footage, you could just recapture a few seconds including the problem part and see if it transcodes OK.