#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. -- Ticket URL: <https://trac.ffmpeg.org/ticket/7045#comment:8> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker _______________________________________________ FFmpeg-trac mailing list FFmpeg-trac@avcodec.org https://ffmpeg.org/mailman/listinfo/ffmpeg-trac To unsubscribe, visit link above, or email ffmpeg-trac-requ...@ffmpeg.org with subject "unsubscribe".