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Diffstat (limited to 'Documentation/media/uapi/v4l/field-order.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/field-order.rst | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/Documentation/media/uapi/v4l/field-order.rst b/Documentation/media/uapi/v4l/field-order.rst index d640e922a974..c422bebe4314 100644 --- a/Documentation/media/uapi/v4l/field-order.rst +++ b/Documentation/media/uapi/v4l/field-order.rst @@ -51,6 +51,11 @@ determined by the video standard. Hence the distinction between temporal and spatial order of fields. The diagrams below should make this clearer. +In V4L it is assumed that all video cameras transmit fields on the media +bus in the same order they were captured, so if the top field was +captured first (is the older field), the top field is also transmitted +first on the bus. + All video capture and output devices must report the current field order. Some drivers may permit the selection of a different order, to this end applications initialize the ``field`` field of struct @@ -101,10 +106,10 @@ enum v4l2_field * - ``V4L2_FIELD_INTERLACED`` - 4 - Images contain both fields, interleaved line by line. The temporal - order of the fields (whether the top or bottom field is first - transmitted) depends on the current video standard. M/NTSC - transmits the bottom field first, all other standards the top - field first. + order of the fields (whether the top or bottom field is older) + depends on the current video standard. In M/NTSC the bottom + field is the older field. In all other standards the top field + is the older field. * - ``V4L2_FIELD_SEQ_TB`` - 5 - Images contain both fields, the top field lines are stored first @@ -135,11 +140,11 @@ enum v4l2_field * - ``V4L2_FIELD_INTERLACED_TB`` - 8 - Images contain both fields, interleaved line by line, top field - first. The top field is transmitted first. + first. The top field is the older field. * - ``V4L2_FIELD_INTERLACED_BT`` - 9 - Images contain both fields, interleaved line by line, top field - first. The bottom field is transmitted first. + first. The bottom field is the older field. |