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In Vegas, NV carries forward last frame before black

 
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TheTooleMan



Joined: 02 Aug 2009
Posts: 3

PostPosted: Mon Aug 10, 2009 3:40 pm    Post subject: In Vegas, NV carries forward last frame before black Reply with quote

I'm using Neat Video in Sony Vegas 6. Here is something that happened after applying NV that you will want to know about - or maybe it has already been reported.

I am aware of the problem concerning repeated frames where NV is being used in a project that contains transitions. The problem I describe below is somewhat different in that no transitions are included in the project where NV is used.

I describe the process below in a manner that allows you to repeat the process.

In step 1 of my process, I rendered a progressive PAL DV file of a complete video that includes several frames of solid color (black) in two places. I created the black frames with Vegas Solid Color media generator, using the preset value "black." The black generated media is inserted in video track 1, while the PAL source media is in track 2. The black media follows a non-black frame in the source media.

Also in step 1, I set a marker several frames after the last frame of the source media. Then I rendered the PAL DV output, including the empty frames at the end of the file up to the last marker. The last frame of the source media contained an image, as the source was cut before the final scene faded completely to black.

In step 2, I applied NV with Temporal Filter Radius set to 2 and Adaptive Filtration turned on. I created a new progressive PAL DV of the NV output. No other processing was done by Vegas in this step.

Looking at the output of step 2, I found that NV carried forward the last non-black frame through the black section of output video. The frame is repeated nearly exactly the same number of frames as there are black frames. (I say "nearly exactly" because the black frames dissolve to the video, and NV does not carry the last non-black frame past this point).

I also see that NV carried forward the last frame of the input file through the empty frames I left at the end of the project.

My hypothesis is that NV is somehow holding and repeating the last non-black frame it encountered, probably to apply it to processing of the next frame. While it may be a good idea to hold the frame in a buffer for comparison to the next frame, NV should not output the frame to fill the black areas of the video.

I hope this helps find a solution to the problem.

Let me know if more information is required.

TheTooleMan
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NVTeam



Joined: 01 Sep 2005
Posts: 2237

PostPosted: Tue Aug 11, 2009 8:05 am    Post subject: Reply with quote

Thank you for the detailed description of the issue. We will try to reproduce it and check what is causing it. I have some initial idea about the cause but we have to check that first.

I will post an update when we get more information.

Thank you,
Vlad
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NVTeam



Joined: 01 Sep 2005
Posts: 2237

PostPosted: Wed Aug 12, 2009 2:14 pm    Post subject: Reply with quote

The promised update is here.

We have been able to identify the cause of the issue. The problem starts with an apparent bug in Vegas (unnecesssary and unexpected dublication of frames in some situations sent to filter plug-in) that exists in all versions from 6 to 9. It only manifests itself when interlaced footage is rendered and only in specific situations. When we encountered that bug several years ago, we developed a special workaround in NV itself, to avoid problems with quality of temporal rendering caused by such dublications. However, we did not make that workaround restricted to the interlaced rendering only, so it is also applies to progressive rendering, most likely unnecessarily. And in cirtumstances when dublicate frames are served by Vegas for reasons other than that bug, that workaround is causing the effect you observed - the last non-dublicate frame to be output. We can restrict the workaround to the interlaced rendering only so the progressive rendering that you do will not be affected and the problem will not be present. However, I guess we will still have to keep the workaround for interlaced rendering because the problems caused by that bug are still there.

We will include this correction in the next regular update of Neat Video for Vegas. If you need it more urgently we can prepare a preliminary build for you. Or you can just reorganize the workflow a bit to avoid situations where you apply NV to such repeating frames. I guess it may be better to apply NV to the original media, so that noise reduction would be the very first post-processing you applied to the footage, which is usually better from the standapoint of noise reduction accuracy.

Kind regards,
Vlad
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