Commit bfd03064 authored by Sakari Ailus's avatar Sakari Ailus Committed by Mauro Carvalho Chehab
Browse files

[media] v4l: Document timestamp buffer flag behaviour 



Timestamp buffer flags are constant at the moment. Document them so that 1)
they're always valid and 2) not changed by the drivers. This leaves room to
extend the functionality later on if needed.

Signed-off-by: default avatarSakari Ailus <sakari.ailus@iki.fi>
Acked-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 309f4d62

Documentation/DocBook/media/v4l/io.xml

+14 −0
Original line number Diff line number Diff line
@@ -653,6 +653,20 @@ plane, are stored in struct <structname>v4l2_plane</structname> instead. 
In that case, struct <structname>v4l2_buffer</structname> contains an array of

plane structures.</para>



    <para>Dequeued video buffers come with timestamps. The driver

    decides at which part of the frame and with which clock the

    timestamp is taken. Please see flags in the masks

    <constant>V4L2_BUF_FLAG_TIMESTAMP_MASK</constant> and

    <constant>V4L2_BUF_FLAG_TSTAMP_SRC_MASK</constant> in <xref

    linkend="buffer-flags" />. These flags are always valid and constant

    across all buffers during the whole video stream. Changes in these

    flags may take place as a side effect of &VIDIOC-S-INPUT; or

    &VIDIOC-S-OUTPUT; however. The

    <constant>V4L2_BUF_FLAG_TIMESTAMP_COPY</constant> timestamp type

    which is used by e.g. on mem-to-mem devices is an exception to the

    rule: the timestamp source flags are copied from the OUTPUT video

    buffer to the CAPTURE video buffer.</para>



    <table frame="none" pgwide="1" id="v4l2-buffer">

      <title>struct <structname>v4l2_buffer</structname></title>

      <tgroup cols="4">

CRA Git | Maintained and supported by SUSTech CRA and CCSE