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IDProjectCategoryView StatusLast Update
0001060DCP-o-maticBugspublic2018-10-17 20:13
Reporterrobn Assigned Tocarl  
PrioritynormalSeveritymajorReproducibilityalways
Status closedResolutionreopened 
PlatformLinuxOSFedoreOS Version25 (64 bit)
Product Version2.10.2 
Summary0001060: DCP-o-matic uses a black frame instead of correct frame before the start of a burned-in subtitle
Description

While testing a DCP created from a Blu-ray I noticed that at several points the image "flashed" a bit when a (burned-in) subtitle appeared.
Further investigation showed that DOM had really replaced a frame with a black frame. This was the frame before the one where the
subtitle should appear first. The subtitle (that should start with the next frame) is also burned-in in this black frame.
Comparing with alternatively burned-in subtitles by ffmpeg I think DOM has a bug.

I tested with DOM 2.10.9 and ffmpeg-3.2.4

Steps To Reproduce
  • generate a DCP with burned-in subtitles from the 20s demo.mkv with DOM

  • extract the jpeg2000 frames from the video-mxf with asdcp-unwrap

  • check the 265th frame: it is black (with a burned-in subtitle)

  • check the 266th frame: it has an image with burned-in subtitle

  • generate images with burned-in subtitles with ffmpeg. For example with something like this:
    ffmpeg -i demo.mkv -filter_complex "[0:v][0:s]overlay[subtitled]" -map '[subtitled]' -pix_fmt rgb24 -f image2 frame-%06d.tiff

  • check the 265th frame: it has an image without burned-in subtitle

  • check the 266th frame: it has an image with burned-in subtitle

I think ffmpeg gets the 265th frame right, while DOM does not.
See the attached images.

Additional Information

One other thing that can be noticed is that DOM appears to scale the (bit-mapped) subtitle.
This degrades quality!
I used a Flat (1998x1080) container to put the HD (1920x1080) video in with the "no scaling" option.
(this results in black bars left&right).
I would expect that DOM does not scale the subtitles. Maybe it scales them to the container used?

The test file I created/used can be found here (68MB):
http://berrymount.nl/dom_sub_bug/demo.mkv

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Activities

robn

2017-03-24 18:46

reporter  

frame265_with_DOM.jpg (47,678 bytes)   
frame265_with_DOM.jpg (47,678 bytes)   
frame265_with_ffmpeg.jpg (390,396 bytes)
frame266_with_DOM.jpg (484,745 bytes)
frame266_with_ffmpeg.jpg (490,148 bytes)

robn

2017-03-26 05:00

reporter   ~0001623

One extra data point:
DOM 2.10.2 does NOT produce the black frame: the proper video frame is used instead.
The subtitle does however also start with this frame (unlike ffmpeg which starts 1 frame later).
(don't know which position is the right one)

carl

2017-05-05 00:45

administrator   ~0001651

Thanks for your investigations... this bug should be gone in 2.11.x, if you'd like to try that?

carl

2017-05-08 09:57

administrator   ~0001655

This should be fixed in current test versions (2.11.x). Do let me know if you see other problems.

robn

2017-05-23 23:58

reporter   ~0001688

Just to confirm: the problem is fixed in 2.11.6 (no more black frames)!

carl

2017-05-24 10:17

administrator   ~0001689

Good, thanks for letting me know.

Bug History

Date Modified Username Field Change
2017-03-24 18:46 robn New Bug
2017-03-24 18:46 robn File Added: frame265_with_DOM.jpg
2017-03-24 18:46 robn File Added: frame265_with_ffmpeg.jpg
2017-03-24 18:46 robn File Added: frame266_with_DOM.jpg
2017-03-24 18:46 robn File Added: frame266_with_ffmpeg.jpg
2017-03-24 23:12 carl Assigned To => carl
2017-03-24 23:12 carl Status new => confirmed
2017-03-26 05:00 robn Note Added: 0001623
2017-05-05 00:45 carl Status confirmed => feedback
2017-05-05 00:45 carl Note Added: 0001651
2017-05-08 09:57 carl Status feedback => resolved
2017-05-08 09:57 carl Resolution open => fixed
2017-05-08 09:57 carl Note Added: 0001655
2017-05-23 23:58 robn Status resolved => feedback
2017-05-23 23:58 robn Resolution fixed => reopened
2017-05-23 23:58 robn Note Added: 0001688
2017-05-24 10:17 carl Status feedback => resolved
2017-05-24 10:17 carl Note Added: 0001689
2018-10-17 20:13 carl Status resolved => closed