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doc/dma-buf: Document usage of SPA_VIDEO_FLAG_MODIFIER flags

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columbarius 2023-07-22 15:17:29 +02:00
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doc/dma-buf.dox
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@ -147,6 +147,18 @@ Therefore consumers should ignore the field `maxsize` of a `spa_data` and the fi
In cases where mapping a single plane is required the size should be obtained locally
via the filedescriptor.
# SPA param video format helpers
SPA offers helper functions to parse and build a spa_pod object to/from the spa_video_info_*
struct. The flags `SPA_VIDEO_FLAG_MODIFIER` and `SPA_VIDEO_FLAG_MODIFIER_FIXATION_REQUIRED`
are used to indicate modifier usage with the format. `SPA_VIDEO_FLAG_MODIFIER` declares the
parsed/provided spa_video_info_* struct contains valid modifier information. For legacy
reasons `spa_format_video_*_build` will announce any modifier != 0 even when this flag is
unused. `SPA_VIDEO_FLAG_MODIFIER_FIXATION_REQUIRED` is exclusive to the parse helpers and
declares that the parsed spa_pod contains modifier information which needs to be fixated as
described aboath. The list of available modifiers has to be parsed manually from the spa_pod
object.
# v4l2
Another use case for streaming via DMA-BUFs are exporting a camera feed from v4l2