media/v4l/field-order.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
3 .. _field-order:
9 We have to distinguish between progressive and interlaced video.
13 odd and even field are transmitted, and due to a small delay between
22 fields are in fact captured at two different instances in time. An
23 object on screen may well move between one field and the next. For
29 combine to frames. We distinguish between top (aka odd) and bottom (aka
43 determined by the video standard. Hence the distinction between temporal
47 In V4L it is assumed that all video cameras transmit fields on the media
48 bus in the same order they were captured, so if the top field was
69 .. flat-table::
70     :header-rows:  0
71     :stub-columns: 0
74     * - ``V4L2_FIELD_ANY``
75       - 0
76       - Applications request this field order when any field format
86     * - ``V4L2_FIELD_NONE``
87       - 1
88       - Images are in progressive (frame-based) format, not interlaced
89         (field-based).
90     * - ``V4L2_FIELD_TOP``
91       - 2
92       - Images consist of the top (aka odd) field only.
93     * - ``V4L2_FIELD_BOTTOM``
94       - 3
95       - Images consist of the bottom (aka even) field only. Applications
99     * - ``V4L2_FIELD_INTERLACED``
100       - 4
101       - Images contain both fields, interleaved line by line. The temporal
103 	depends on the current video standard. In M/NTSC the bottom
104 	field is the older field. In all other standards the top field
106     * - ``V4L2_FIELD_SEQ_TB``
107       - 5
108       - Images contain both fields, the top field lines are stored first
109 	in memory, immediately followed by the bottom field lines. Fields
110 	are always stored in temporal order, the older one first in
112     * - ``V4L2_FIELD_SEQ_BT``
113       - 6
114       - Images contain both fields, the bottom field lines are stored
115 	first in memory, immediately followed by the top field lines.
116 	Fields are always stored in temporal order, the older one first in
118     * - ``V4L2_FIELD_ALTERNATE``
119       - 7
120       - The two fields of a frame are passed in separate buffers, in
127 	any dropped fields between them (fields can drop individually),
133     * - ``V4L2_FIELD_INTERLACED_TB``
134       - 8
135       - Images contain both fields, interleaved line by line, top field
137     * - ``V4L2_FIELD_INTERLACED_BT``
138       - 9
139       - Images contain both fields, interleaved line by line, top field
144 .. _fieldseq-tb:
149 .. kernel-figure:: fieldseq_tb.svg
156 .. _fieldseq-bt:
161 .. kernel-figure:: fieldseq_bt.svg