Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
 |  undetermined
  Version:  unspecified  |   Resolution:
 Keywords:   |   Blocked By:
 Blocking:   |  Reproduced by developer:  0
Analyzed by developer:  0|
-+-
Changes (by danielkaiser):

 * Attachment "mov_pixeldensity.patch" added.


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Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
 |  undetermined
  Version:  unspecified  |   Resolution:
 Keywords:   |   Blocked By:
 Blocking:   |  Reproduced by developer:  0
Analyzed by developer:  0|
-+-
Changes (by danielkaiser):

 * cc: daniel.kaiser94@… (added)


Comment:

 I recently implemented this feature to generate mov files for HiDPI
 screens. And unlike mentioned in the previous comment a bit more data is
 required for this feature to work properly, but it also offers more
 possibilities than simply showing videos in half scale.

 As already mentioned the `com.apple.quicktime.pixeldensity` metadata tag
 is required in the `trak` meta atom followed by a value of 0x30. However
 0x30 is not the actual value of this metadata tag but the size of the
 following `ilst` atom which (among other things) includes 16 Bytes of data
 representing 4 uint32_t. The first pair of these values seems to specify
 the actual pixel resolution of the video stream, the second specifies the
 desired playback resolution (unfortunately, I wasn't able to find any
 documentation from Apple proving this, but regarding my tests it is almost
 certainly the case). This allows arbitrary playback resolutions to be
 defined through the metadata.

 Attached is a diff based on ffmpeg version 4.2.1 adding this feature to
 mov encoding using the `write_pixeldensity` flag. This is a quick-and-
 dirty implementation with the primary aim to keep the patch simple and
 small setting the playback resolution to a fixed half scale. This code is
 far from production ready and containing ''a lot'' of hard-coded values
 but it might be a help for someone who wants to implement this properly.

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Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
 |  undetermined
  Version:  unspecified  |   Resolution:
 Keywords:   |   Blocked By:
 Blocking:   |  Reproduced by developer:  0
Analyzed by developer:  0|
-+-

Comment (by hughes):

 Specifically, it has a value of 0x30 prior to conversion. Confirmed that
 setting it to any other value seems to revert the lower DPI during
 playback.

 This metadata is actually part of the `trak` atom meta, not the `moov`
 meta.

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Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
 |  undetermined
  Version:  unspecified  |   Resolution:
 Keywords:   |   Blocked By:
 Blocking:   |  Reproduced by developer:  0
Analyzed by developer:  0|
-+-

Comment (by hughes):

 This seems to be caused by dropping the `com.apple.quicktime.pixeldensity`
 metadata tag. It's present in the movie atoms prior to conversion, but
 absent after.

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Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
  Version:  unspecified  |  undetermined
 Keywords:   |   Resolution:
 Blocking:   |   Blocked By:
Analyzed by developer:  0|  Reproduced by developer:  0
-+-

Comment (by cehoyos):

 Is the issue also reproducible with the following command line?
 {{{
 $ ffmpeg -i retina_sample.mov -vcodec copy out.mov
 }}}

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Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
  Version:  unspecified  |  undetermined
 Keywords:   |   Resolution:
 Blocking:   |   Blocked By:
Analyzed by developer:  0|  Reproduced by developer:  0
-+-

Comment (by moubry):

 Replying to [comment:3 cehoyos]:
 > Please test current FFmpeg git head and provide the command line you
 tested together with the complete, uncut console output and upload an
 input file to make this a valid ticket.

 I've added the things you've asked for. I reinstalled ffmpeg from head,
 compressed a sample video, and attached the terminal output as well as the
 before and after videos. I hope this helps!

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Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
  Version:  unspecified  |  undetermined
 Keywords:   |   Resolution:
 Blocking:   |   Blocked By:
Analyzed by developer:  0|  Reproduced by developer:  0
-+-
Changes (by cehoyos):

 * keywords:  quicktime =>
 * version:  3.4 => unspecified


Comment:

 Please test current FFmpeg git head and provide the command line you
 tested together with the complete, uncut console output and upload an
 input file to make this a valid ticket.

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Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
  Version:  3.4  |  undetermined
 Keywords:  quicktime|   Resolution:
 Blocking:   |   Blocked By:
Analyzed by developer:  0|  Reproduced by developer:  0
-+-
Changes (by moubry):

 * cc: sean+ffmpeg@… (added)
 * keywords:   => quicktime
 * version:  unspecified => 3.4


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Re: [FFmpeg-trac] #7045(undetermined:new): Should retain pixel density metadata from HiDPI/Retina screen recordings

[FFmpeg]

#7045: Should retain pixel density metadata from HiDPI/Retina screen recordings
-+-
 Reporter:  moubry   |Owner:
 Type:  defect   |   Status:  new
 Priority:  normal   |Component:
  Version:  unspecified  |  undetermined
 Keywords:   |   Resolution:
 Blocking:   |   Blocked By:
Analyzed by developer:  0|  Reproduced by developer:  0
-+-

Comment (by moubry):

 For the record, VLC plays both videos too big (blurry). So being able to
 play HiDPI videos at the expected pixel density seems to be a feature of
 QuickTime Player.

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