Em Fri, 7 Mar 2014 15:26:24 +0100 Hans Verkuil <hverkuil@xxxxxxxxx> escreveu: > From: Hans Verkuil <hans.verkuil@xxxxxxxxx> > > Be more specific with regards to how some of these fields are interpreted. > In particular height vs field and which fields can be set by the application. > > Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> > --- > Documentation/DocBook/media/v4l/pixfmt.xml | 33 +++++++++++++++++++++++------- > 1 file changed, 26 insertions(+), 7 deletions(-) > > diff --git a/Documentation/DocBook/media/v4l/pixfmt.xml b/Documentation/DocBook/media/v4l/pixfmt.xml > index f586d34..7b0b098 100644 > --- a/Documentation/DocBook/media/v4l/pixfmt.xml > +++ b/Documentation/DocBook/media/v4l/pixfmt.xml > @@ -25,7 +25,18 @@ capturing and output, for overlay frame buffer formats see also > <row> > <entry>__u32</entry> > <entry><structfield>height</structfield></entry> > - <entry>Image height in pixels.</entry> > + <entry>Image height in pixels. If <structfield>field</structfield> is > + one of <constant>V4L2_FIELD_TOP</constant>, <constant>V4L2_FIELD_BOTTOM</constant> > + or <constant>V4L2_FIELD_ALTERNATE</constant> then height refers to the > + number of lines in the field, otherwise it refers to the number of > + lines in the frame (which is twice the field height for interlaced > + formats). In case of conflicts between the <structfield>height</structfield> > + value and the <structfield>field</structfield> value, the > + <structfield>height</structfield> shall be the deciding factor. > + So if <structfield>height</structfield> is set to 480 for an NTSC-M > + standard, and <structfield>field</structfield> is set to > + <constant>V4L2_FIELD_TOP</constant>, then <structfield>field</structfield> > + shall be adjusted to ⪚ <constant>V4L2_FIELD_INTERLACED</constant>.</entry> This seems to be a description of a hack. I think we should better discuss the meanings for V4L2_FIELD on some next mini-summit, as this seem to be very confusing. I'm not even sure if applications use it properly, as some drivers never implemented it right. > </row> > <row> > <entry spanname="hspan">Applications set these fields to > @@ -54,7 +65,11 @@ linkend="reserved-formats" /></entry> > can request to capture or output only the top or bottom field, or both > fields interlaced or sequentially stored in one buffer or alternating > in separate buffers. Drivers return the actual field order selected. > -For details see <xref linkend="field-order" />.</entry> > +In case of conflicts between the <structfield>height</structfield> and > +<structfield>field</structfield> values, the <structfield>height</structfield> > +value will be the deciding factor. See also the description of > +<structfield>height</structfield> above. > +For more details on fields see <xref linkend="field-order" />.</entry> > </row> > <row> > <entry>__u32</entry> > @@ -81,7 +96,10 @@ plane and is divided by the same factor as the > example the Cb and Cr planes of a YUV 4:2:0 image have half as many > padding bytes following each line as the Y plane. To avoid ambiguities > drivers must return a <structfield>bytesperline</structfield> value > -rounded up to a multiple of the scale factor.</para></entry> > +rounded up to a multiple of the scale factor.</para> > +<para>For compressed formats the <structfield>bytesperline</structfield> > +value makes no sense. Applications and drivers must set this to 0 in > +that case.</para></entry> > </row> > <row> > <entry>__u32</entry> > @@ -97,7 +115,8 @@ hold an image.</entry> > <entry>&v4l2-colorspace;</entry> > <entry><structfield>colorspace</structfield></entry> > <entry>This information supplements the > -<structfield>pixelformat</structfield> and must be set by the driver, > +<structfield>pixelformat</structfield> and must be set by the driver for > +capture streams and by the application for output streams, > see <xref linkend="colorspaces" />.</entry> > </row> > <row> > @@ -135,7 +154,7 @@ set this field to zero.</entry> > <entry>__u16</entry> > <entry><structfield>bytesperline</structfield></entry> > <entry>Distance in bytes between the leftmost pixels in two adjacent > - lines.</entry> > + lines. See &v4l2-pix-format;.</entry> > </row> > <row> > <entry>__u16</entry> > @@ -154,12 +173,12 @@ set this field to zero.</entry> > <row> > <entry>__u32</entry> > <entry><structfield>width</structfield></entry> > - <entry>Image width in pixels.</entry> > + <entry>Image width in pixels. See &v4l2-pix-format;.</entry> > </row> > <row> > <entry>__u32</entry> > <entry><structfield>height</structfield></entry> > - <entry>Image height in pixels.</entry> > + <entry>Image height in pixels. See &v4l2-pix-format;.</entry> > </row> > <row> > <entry>__u32</entry> -- Regards, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
