View Bug Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0002681 | DCP-o-matic | Bugs | public | 2023-12-08 19:42 | 2024-01-09 20:30 |
| Reporter | overlookmotel | Assigned To | carl | ||
| Priority | normal | Severity | minor | Reproducibility | always |
| Status | resolved | Resolution | fixed | ||
| Platform | Mac | OS | OS X | OS Version | 10.13 |
| Product Version | 2.16.70 | ||||
| Target Version | 2.16.71 | ||||
| Summary | 0002681: Alpha channel not rendered correctly in ProRes4444 files | ||||
| Description | I've noticed this for a long time, but only just getting around to making a repro case. When DOM is given a ProRes4444 file with alpha channel, DOM appears to ignore the alpha channel. This results in blocky graphics and text where smoothing of the edges relies on the alpha channel. Probably it's bad practice to deliver a master without alpha channel flattened, but nonetheless it's not uncommon to find on end credits and other graphics (e.g. white text on a transparent background). I guess it's arguable that DOM shouldn't pay attention to the alpha channel, because that raises the question of what colour DOM should render transparent as. However, the standard in most editing software is to render transparent as black, so I don't think it'd be surprising to users if DOM did the same. | ||||
| Steps To Reproduce | Open a ProRes4444 file with alpha channel in DCP-o-matic. The result is immediately visible in the preview. The output in DCP is identical to the preview. I'll post a repro case shortly. | ||||
| Tags | No tags attached. | ||||
| Branch | 2681-alpha | ||||
| Estimated weeks required | |||||
| Estimated work required | Small | ||||
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Repro case: https://drive.google.com/file/d/1suyrXfwJAmCTQqhteFIthFjWpUoqAsFw This contains:
When viewing the source ProRes in e.g. VLC or Quicktime, it appears as a white circle with soft blurry edges. The DCP renders it as a larger circle with hard, blocky edges. My assumption is that this is the image contained in the video's YUV channels, without taking into account the alpha channel. |
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PS: Same effect occurs with other image formats which support alpha channels e.g. TIFFs. However, it's far less of a problem with stills, as you'll spot it immediately. A graphic buried somewhere in a feature-length video is much easier to miss. |
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Here's a TIFF with transparency, if it's useful for testing: |
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Done, needs tests to be run. |
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Thanks for another great bug report! @carl fixed in |
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Thank you Carl! |
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Has this made it into a release yet? We have a couple of films with this problem that we need to make DCPs from, so would be a good opportunity to check the fix. If you're on holiday Carl, don't tear yourself away from the turkey! We can work around it other ways for now, and there'll be other opportunities to test the fix no doubt. |
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@overlookmotel I just uploaded 2.16.71 with this fix in, thanks for testing! |
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Confirmed it works on one the ProRes4444 HQ files we have received recently with an alpha channel. There is one small oddity: If you create a project in DOM 2.14.x using a source with an alpha channel, when you open that project in 2.16.71, the alpha channel does not get recognised, and "premultiply" does not happen. i.e. result is same as before this fix. I guess something in I don't think that really matters much! Not many people will be switching between 2.14.x and 2.16.x willy nilly. Just mentioning it as I happened to notice it. |
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Right, when the content is examined a suitable video filter is inserted into chain if the source has an alpha channel. We could force re-examination of 2.14.x projects in 2.16.x but that feels a little like a sledgehammer to crack a nut (and might cause other problems I guess). |
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Yes, I don't think the sledgehammer is necessary! |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2023-12-08 19:42 | overlookmotel | New Bug | |
| 2023-12-08 19:48 | overlookmotel | Note Added: 0006129 | |
| 2023-12-08 19:52 | overlookmotel | Note Added: 0006130 | |
| 2023-12-08 19:54 | overlookmotel | Note Added: 0006131 | |
| 2023-12-08 19:54 | overlookmotel | File Added: blob.tiff.zip | |
| 2023-12-08 21:36 | carl | Status | new => acknowledged |
| 2023-12-08 21:36 | carl | Target Version | => 2.16.71 |
| 2023-12-08 21:36 | carl | Estimated work required | => Undecided |
| 2023-12-09 19:32 | carl | Branch | => 2681-alpha |
| 2023-12-09 19:32 | carl | Estimated work required | Undecided => Small |
| 2023-12-09 19:32 | carl | Assigned To | => carl |
| 2023-12-09 19:32 | carl | Status | acknowledged => in progress |
| 2023-12-10 22:52 | carl | Note Added: 0006133 | |
| 2023-12-11 13:07 | carl | Status | in progress => tests running |
| 2023-12-12 14:05 | carl | Status | tests running => resolved |
| 2023-12-12 14:05 | carl | Resolution | open => fixed |
| 2023-12-12 14:05 | carl | Note Added: 0006143 | |
| 2023-12-12 18:24 | overlookmotel | Note Added: 0006144 | |
| 2023-12-29 18:41 | overlookmotel | Note Added: 0006170 | |
| 2023-12-31 19:36 | carl | Note Added: 0006173 | |
| 2024-01-03 20:27 | overlookmotel | Note Added: 0006189 | |
| 2024-01-03 21:24 | carl | Note Added: 0006190 | |
| 2024-01-04 16:28 | overlookmotel | Note Added: 0006194 | |
| 2024-01-09 20:30 | carl | Relationship added | related to 0002564 |
