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Please Help!!! Distortion visible from camera flash

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marcin idzikowski
Please Help!!! Distortion visible from camera flash
on Dec 8, 2007 at 3:09:26 am

Hi, Looking for some answers here don't know what to do. I filmed my first wedding for a friend. I used Premier Pro 2.0 to put the movie together and everything went great. I imported the movie to Encore, made the menus and completed the DVD. The problem is that when i watched the dvd, i notice every time that the photographer took a photo and the flash burst came out my video looks distorted. When i pause the video it shows the white flash from the photo camera and a bunch of distorted lines on the screen. It looks really bad. This did not show in premier pro and encore before the video was burned unto the dvd. I used double ayer dvds. Did i miss something when the movie went from avi to mpeg-2. Hope tis is as much info as needed. If i missed anything please let me know and ill try to answer whatever is needed. Please Help.
Newbie


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Alessio Gemma
Re: Please Help!!! Distortion visible from camera flash
on Dec 9, 2007 at 8:42:01 pm

Hello,
it's a known issue.. some camcorders have this problem.
I think it's cause of the camera, not of the compression: I've a Sony V1 and it's affected by the same problem.. it could be interesting to discuss about this argument.
Any time there's a photographer near me when I'm shooting, if he take pictures with flash, in my tapes I see a blank frame ( all blank)... it's horrible!
Maybe someone can help us.

Regards,
Alessio



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Heath Firestone
Re: Please Help!!! Distortion visible from camera flash
on Dec 11, 2007 at 6:57:42 am

If the distortion isn't on the original footage, then it is probably artifacting caused by too much change in too short of a timespan. Temporal compression, in this case, a full frame only every fifteen frames (1/2 second), has problems when too much information changes in the span of a few frames, as is the case when a flash fires. To correct fort his, make sure you are encoding two pass VBR, preferably at 7Mbps. Variable Bitrate Compression allocates more bandwidth when needed to compensate for things like this. Two pass encoding takes twice as long, but the first time through it analyzes the footage, so it can do a higher quality encode on the second pass.

Hope this solves your problem,

Heath


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Alessio Gemma
Re: Please Help!!! Distortion visible from camera flash
on Dec 11, 2007 at 11:17:54 am

Heath,
I thought it was that you described, but I'm sure the problem is on the camcorder.
When I capture from the HDV tape (using HDMI interface) I can monitor the capturing on a big LCD in real time, thanks to Intensity card: well, when there's a flash camera, the videostream becomes "all white" for some frames, even if the flash is quite far from the camcorder.
I captured a clip and I compressed it with a 2pass encoding without any kind of ediding: well, the final compressed clip has the same artifact and it looks amplified too!
Maybe it could be useful to post a sample somewhere.
Regards,
Alessio


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Heath Firestone
Re: Please Help!!! Distortion visible from camera flash
on Dec 11, 2007 at 4:42:22 pm

In your original post, you said that this did not show in Premiere and Encore before burning to DVD.

We're probably still talking about temporal compression artifacting, since HDV also employs temporal compression.

If this is how the original footage looks, then there is nothing you can do about it at this point.

Out of curiosity, why are you capturing HDV through HDMI with an Intensity card? You'd probably be better off capturing over firewire, so that it doesn't have to uncompress, then recompress, as it would if you captured from HDMI. HDMI capture will only provide a superior quality capture if you are doing a live feed. Once you've laid it to tape, you've already compressed it, so you want to try to keep your levels of recompression to a minimum.

Heath


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Alessio Gemma
Re: Please Help!!! Distortion visible from camera flash
on Dec 11, 2007 at 8:14:21 pm

[Heath] "In your original post, you said that this did not show in Premiere and Encore before burning to DVD."

I work with Final Cut and Media 100, who posted the thread works with Premiere, Marcin Idzikowski.

[Heath] "We're probably still talking about temporal compression artifacting, since HDV also employs temporal compression. If this is how the original footage looks, then there is nothing you can do about it at this point."

Yeah, I can't do anything, I know.. it's an issue of my camcorder, Sony V1E, because with the previous one I never had this problem.

[Heath] "Out of curiosity, why are you capturing HDV through HDMI with an Intensity card? You'd probably be better off capturing over firewire, so that it doesn't have to uncompress, then recompress, as it would if you captured from HDMI. HDMI capture will only provide a superior quality capture if you are doing a live feed. Once you've laid it to tape, you've already compressed it, so you want to try to keep your levels of recompression to a minimum."

Yeah, you're right. Capturing from HDMI gives me the same quality than HDV capturing.
Anyway, I still edit in Media 100 Producer: there's no native support to HDV in this software, so capturing full HD footage at 1920x1080 from HDMI gives me the opportunity to fast import the captured clip in Media 100 (it only accepts SD or HD formas).. this's all... maybe it's not a good workflow, but it works great and the final DVD quality is excellent (much more than DVCAM tapes).

Heath, you sounds an expert, so I'd like to ask you something..
I'd like to downconvert some captured clips from HD/HDV to SD: I didn't do it in hardware, because I see some strobe effects in the captured clips (I'm sure my FCP settings are right, they work fine with HDV and HDMI capturing, but not with HDV->DV downconverting).
So, is there a good workflow to downconvert in software, using Apple Compressor?

Best regards,
Alessio




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