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IDProjectCategoryView StatusDate SubmittedLast Update
0000730KdenliveRenderingpublic2009-03-22 16:552009-06-18 01:44
Assigned Toddennedy 
PlatformOSOS Version
Product Version0.7.2 
Target VersionFixed in Version0.7.3 
Summary0000730: Rendering with transitions degrades quality unacceptably
DescriptionSimple project demonstrating unacceptable (and unwarrented) degredation of quality in rendered video...

The video in the preview interface seems perfect, but when rendering to any output format (I've tried mpeg2 at the highest bitrate and rawdv), the section of text which involves a transition is broken.

I've uploaded a test project which shows the bug with a simple text PNG (with alpha transparancy) and a colour clip. [^] shows the image from the first 5 seconds of the rendered clip, with [^] showing the image after.

As can be seen, the text has horrible "mice teeth" type effects.

I believe that the horizontal lines are being exported in the wrong order somehow (e.g. 2, 1, 4, 3, 6, 5, 8, 7, 10, 9). Note that this test project only includes a colour clip and a png file; so I don't think it can be an issue with incorrectly specifying the input interlace order.
Additional Information [^]
TagsNo tags attached.
Build/Install MethodDistribution package
Attached Filespng file icon alpha_combination.png [^] (128,848 bytes) 2009-03-22 16:55

- Relationships

-  Notes
gnomeking (reporter)
2009-03-22 16:57

Just a little note to say that it appears to be that the render is inconsistent over whether to use interlaced mode or not. The project starts in progressive mode, then changes to interlaced mode when the transition starts.
subik (reporter)
2009-04-06 19:05

I can confirm this behaviour. I can "workaround" it a bit when I set "Scanning: Force Progressive" in the Rendering dialog
ddennedy (developer)
2009-04-09 09:26

This is called field-based rendering, which is appropriate when animating composites. It is on by default when the project or render setting is not progressive. MLT provides the option to disable this on a per effect basis. So, kdenlive needs an enhancement to use and expose that.
ddennedy (developer)
2009-04-11 08:52

I sat down to expose this MLT progressive rendering option in kdenlive when I realized it was already added! I reviewed the source history, and indeed it was not in 0.7.2. It is in SVN and the soon to be released 0.7.3. It is named "Force Progressive Rendering" in the Composite transition's settings window. I am considering a change to make this default to on.

Also, as subik reported, forcing progressive in the render setting does prevent this, but that is not always desirable. One often wants interlace output (e.g. DVD) but when not animating the composite, you do not want field-based rendering.
ddennedy (developer)
2009-04-11 08:58

Re: I believe that the horizontal lines are being exported in the wrong order

MLT intentionally renders bottom-field-first (fyi, DV is bottom field first). This alone is not a huge issue. A more significant issue is when combining videos with different field orders. Fortunately, MLT normalizes field order to take care of this. I have confirmed correct field order normalization and field-based rendering with commerical broadcast television customers and equipment for which MLT was designed. They often need to animate titles and graphical overlays.

- Issue History
Date Modified Username Field Change
2009-03-22 16:55 gnomeking New Issue
2009-03-22 16:55 gnomeking File Added: alpha_combination.png
2009-03-22 16:55 gnomeking Build/Install Method => Distribution package
2009-03-22 16:57 gnomeking Note Added: 0002574
2009-04-06 19:05 subik Note Added: 0002667
2009-04-09 09:26 ddennedy Note Added: 0002681
2009-04-11 08:52 ddennedy Note Added: 0002700
2009-04-11 08:52 ddennedy Status new => resolved
2009-04-11 08:52 ddennedy Fixed in Version => 0.7.3
2009-04-11 08:52 ddennedy Resolution open => fixed
2009-04-11 08:52 ddennedy Assigned To => ddennedy
2009-04-11 08:58 ddennedy Note Added: 0002701
2009-06-18 01:44 xzhayon Status resolved => closed

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