diff options
| author | Mauro Carvalho Chehab <mchehab@redhat.com> | 2009-09-14 03:16:04 +0200 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2009-09-19 04:47:55 +0200 |
| commit | 8e080c2e6cadada82a6b520e0c23a1cb974822d5 (patch) | |
| tree | 991450ff1abba98e5313906478c33816a202ccab /Documentation/DocBook/v4l/pixfmt.xml | |
| parent | V4L/DVB (12756): af9015: fix typo in register compare (diff) | |
| download | linux-8e080c2e6cadada82a6b520e0c23a1cb974822d5.tar.xz linux-8e080c2e6cadada82a6b520e0c23a1cb974822d5.zip | |
V4L/DVB (12761): DocBook: add media API specs
The V4L and DVB API's are there for a long time. however, up to now,
no efforts were done to merge them to kernel DocBook.
This patch adds the current versions of the specs as an unique compendium.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'Documentation/DocBook/v4l/pixfmt.xml')
| -rw-r--r-- | Documentation/DocBook/v4l/pixfmt.xml | 796 |
1 files changed, 796 insertions, 0 deletions
diff --git a/Documentation/DocBook/v4l/pixfmt.xml b/Documentation/DocBook/v4l/pixfmt.xml new file mode 100644 index 000000000000..aaea55d44592 --- /dev/null +++ b/Documentation/DocBook/v4l/pixfmt.xml @@ -0,0 +1,796 @@ + <title>Image Formats</title> + + <para>The V4L2 API was primarily designed for devices exchanging +image data with applications. The +<structname>v4l2_pix_format</structname> structure defines the format +and layout of an image in memory. Image formats are negotiated with +the &VIDIOC-S-FMT; ioctl. (The explanations here focus on video +capturing and output, for overlay frame buffer formats see also +&VIDIOC-G-FBUF;.)</para> + + <table pgwide="1" frame="none" id="v4l2-pix-format"> + <title>struct <structname>v4l2_pix_format</structname></title> + <tgroup cols="3"> + &cs-str; + <tbody valign="top"> + <row> + <entry>__u32</entry> + <entry><structfield>width</structfield></entry> + <entry>Image width in pixels.</entry> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>height</structfield></entry> + <entry>Image height in pixels.</entry> + </row> + <row> + <entry spanname="hspan">Applications set these fields to +request an image size, drivers return the closest possible values. In +case of planar formats the <structfield>width</structfield> and +<structfield>height</structfield> applies to the largest plane. To +avoid ambiguities drivers must return values rounded up to a multiple +of the scale factor of any smaller planes. For example when the image +format is YUV 4:2:0, <structfield>width</structfield> and +<structfield>height</structfield> must be multiples of two.</entry> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>pixelformat</structfield></entry> + <entry>The pixel format or type of compression, set by the +application. This is a little endian <link +linkend="v4l2-fourcc">four character code</link>. V4L2 defines +standard RGB formats in <xref linkend="rgb-formats" />, YUV formats in <xref +linkend="yuv-formats" />, and reserved codes in <xref +linkend="reserved-formats" /></entry> + </row> + <row> + <entry>&v4l2-field;</entry> + <entry><structfield>field</structfield></entry> + <entry>Video images are typically interlaced. Applications +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> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>bytesperline</structfield></entry> + <entry>Distance in bytes between the leftmost pixels in two +adjacent lines.</entry> + </row> + <row> + <entry spanname="hspan"><para>Both applications and drivers +can set this field to request padding bytes at the end of each line. +Drivers however may ignore the value requested by the application, +returning <structfield>width</structfield> times bytes per pixel or a +larger value required by the hardware. That implies applications can +just set this field to zero to get a reasonable +default.</para><para>Video hardware may access padding bytes, +therefore they must reside in accessible memory. Consider cases where +padding bytes after the last line of an image cross a system page +boundary. Input devices may write padding bytes, the value is +undefined. Output devices ignore the contents of padding +bytes.</para><para>When the image format is planar the +<structfield>bytesperline</structfield> value applies to the largest +plane and is divided by the same factor as the +<structfield>width</structfield> field for any smaller planes. For +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> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>sizeimage</structfield></entry> + <entry>Size in bytes of the buffer to hold a complete image, +set by the driver. Usually this is +<structfield>bytesperline</structfield> times +<structfield>height</structfield>. When the image consists of variable +length compressed data this is the maximum number of bytes required to +hold an image.</entry> + </row> + <row> + <entry>&v4l2-colorspace;</entry> + <entry><structfield>colorspace</structfield></entry> + <entry>This information supplements the +<structfield>pixelformat</structfield> and must be set by the driver, +see <xref linkend="colorspaces" />.</entry> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>priv</structfield></entry> + <entry>Reserved for custom (driver defined) additional +information about formats. When not used drivers and applications must +set this field to zero.</entry> + </row> + </tbody> + </tgroup> + </table> + + <section> + <title>Standard Image Formats</title> + + <para>In order to exchange images between drivers and +applications, it is necessary to have standard image data formats +which both sides will interpret the same way. V4L2 includes several +such formats, and this section is intended to be an unambiguous +specification of the standard image data formats in V4L2.</para> + + <para>V4L2 drivers are not limited to these formats, however. +Driver-specific formats are possible. In that case the application may +depend on a codec to convert images to one of the standard formats +when needed. But the data can still be stored and retrieved in the +proprietary format. For example, a device may support a proprietary +compressed format. Applications can still capture and save the data in +the compressed format, saving much disk space, and later use a codec +to convert the images to the X Windows screen format when the video is +to be displayed.</para> + + <para>Even so, ultimately, some standard formats are needed, so +the V4L2 specification would not be complete without well-defined +standard formats.</para> + + <para>The V4L2 standard formats are mainly uncompressed formats. The +pixels are always arranged in memory from left to right, and from top +to bottom. The first byte of data in the image buffer is always for +the leftmost pixel of the topmost row. Following that is the pixel +immediately to its right, and so on until the end of the top row of +pixels. Following the rightmost pixel of the row there may be zero or +more bytes of padding to guarantee that each row of pixel data has a +certain alignment. Following the pad bytes, if any, is data for the +leftmost pixel of the second row from the top, and so on. The last row +has just as many pad bytes after it as the other rows.</para> + + <para>In V4L2 each format has an identifier which looks like +<constant>PIX_FMT_XXX</constant>, defined in the <link +linkend="videodev">videodev.h</link> header file. These identifiers +represent <link linkend="v4l2-fourcc">four character codes</link> +which are also listed below, however they are not the same as those +used in the Windows world.</para> + </section> + + <section id="colorspaces"> + <title>Colorspaces</title> + + <para>[intro]</para> + + <!-- See proposal by Billy Biggs, video4linux-list@redhat.com +on 11 Oct 2002, subject: "Re: [V4L] Re: v4l2 api", and +http://vektor.theorem.ca/graphics/ycbcr/ and +http://www.inforamp.net/~poynton/notes/colour_and_gamma/index.html --> + + <para> + <variablelist> + <varlistentry> + <term>Gamma Correction</term> + <listitem> + <para>[to do]</para> + <para>E'<subscript>R</subscript> = f(R)</para> + <para>E'<subscript>G</subscript> = f(G)</para> + <para>E'<subscript>B</subscript> = f(B)</para> + </listitem> + </varlistentry> + <varlistentry> + <term>Construction of luminance and color-difference +signals</term> + <listitem> + <para>[to do]</para> + <para>E'<subscript>Y</subscript> = +Coeff<subscript>R</subscript> E'<subscript>R</subscript> ++ Coeff<subscript>G</subscript> E'<subscript>G</subscript> ++ Coeff<subscript>B</subscript> E'<subscript>B</subscript></para> + <para>(E'<subscript>R</subscript> - E'<subscript>Y</subscript>) = E'<subscript>R</subscript> +- Coeff<subscript>R</subscript> E'<subscript>R</subscript> +- Coeff<subscript>G</subscript> E'<subscript>G</subscript> +- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para> + <para>(E'<subscript>B</subscript> - E'<subscript>Y</subscript>) = E'<subscript>B</subscript> +- Coeff<subscript>R</subscript> E'<subscript>R</subscript> +- Coeff<subscript>G</subscript> E'<subscript>G</subscript> +- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para> + </listitem> + </varlistentry> + <varlistentry> + <term>Re-normalized color-difference signals</term> + <listitem> + <para>The color-difference signals are scaled back to unity +range [-0.5;+0.5]:</para> + <para>K<subscript>B</subscript> = 0.5 / (1 - Coeff<subscript>B</subscript>)</para> + <para>K<subscript>R</subscript> = 0.5 / (1 - Coeff<subscript>R</subscript>)</para> + <para>P<subscript>B</subscript> = +K<subscript>B</subscript> (E'<subscript>B</subscript> - E'<subscript>Y</subscript>) = + 0.5 (Coeff<subscript>R</subscript> / Coeff<subscript>B</subscript>) E'<subscript>R</subscript> ++ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>B</subscript>) E'<subscript>G</subscript> ++ 0.5 E'<subscript>B</subscript></para> + <para>P<subscript>R</subscript> = +K<subscript>R</subscript> (E'<subscript>R</subscript> - E'<subscript>Y</subscript>) = + 0.5 E'<subscript>R</subscript> ++ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>R</subscript>) E'<subscript>G</subscript> ++ 0.5 (Coeff<subscript>B</subscript> / Coeff<subscript>R</subscript>) E'<subscript>B</subscript></para> + </listitem> + </varlistentry> + <varlistentry> + <term>Quantization</term> + <listitem> + <para>[to do]</para> + <para>Y' = (Lum. Levels - 1) · E'<subscript>Y</subscript> + Lum. Offset</para> + <para>C<subscript>B</subscript> = (Chrom. Levels - 1) +· P<subscript>B</subscript> + Chrom. Offset</para> + <para>C<subscript>R</subscript> = (Chrom. Levels - 1) +· P<subscript>R</subscript> + Chrom. Offset</para> + <para>Rounding to the nearest integer and clamping to the range +[0;255] finally yields the digital color components Y'CbCr +stored in YUV images.</para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <example> + <title>ITU-R Rec. BT.601 color conversion</title> + + <para>Forward Transformation</para> + + <programlisting> +int ER, EG, EB; /* gamma corrected RGB input [0;255] */ +int Y1, Cb, Cr; /* output [0;255] */ + +double r, g, b; /* temporaries */ +double y1, pb, pr; + +int +clamp (double x) +{ + int r = x; /* round to nearest */ + + if (r < 0) return 0; + else if (r > 255) return 255; + else return r; +} + +r = ER / 255.0; +g = EG / 255.0; +b = EB / 255.0; + +y1 = 0.299 * r + 0.587 * g + 0.114 * b; +pb = -0.169 * r - 0.331 * g + 0.5 * b; +pr = 0.5 * r - 0.419 * g - 0.081 * b; + +Y1 = clamp (219 * y1 + 16); +Cb = clamp (224 * pb + 128); +Cr = clamp (224 * pr + 128); + +/* or shorter */ + +y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB; + +Y1 = clamp ( (219 / 255.0) * y1 + 16); +Cb = clamp (((224 / 255.0) / (2 - 2 * 0.114)) * (EB - y1) + 128); +Cr = clamp (((224 / 255.0) / (2 - 2 * 0.299)) * (ER - y1) + 128); + </programlisting> + + <para>Inverse Transformation</para> + + <programlisting> +int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */ +int ER, EG, EB; /* output [0;255] */ + +double r, g, b; /* temporaries */ +double y1, pb, pr; + +int +clamp (double x) +{ + int r = x; /* round to nearest */ + + if (r < 0) return 0; + else if (r > 255) return 255; + else return r; +} + +y1 = (255 / 219.0) * (Y1 - 16); +pb = (255 / 224.0) * (Cb - 128); +pr = (255 / 224.0) * (Cr - 128); + +r = 1.0 * y1 + 0 * pb + 1.402 * pr; +g = 1.0 * y1 - 0.344 * pb - 0.714 * pr; +b = 1.0 * y1 + 1.772 * pb + 0 * pr; + +ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */ +EG = clamp (g * 255); +EB = clamp (b * 255); + </programlisting> + </example> + + <table pgwide="1" id="v4l2-colorspace" orient="land"> + <title>enum v4l2_colorspace</title> + <tgroup cols="11" align="center"> + <colspec align="left" /> + <colspec align="center" /> + <colspec align="left" /> + <colspec colname="cr" /> + <colspec colname="cg" /> + <colspec colname="cb" /> + <colspec colname="wp" /> + <colspec colname="gc" /> + <colspec colname="lum" /> + <colspec colname="qy" /> + <colspec colname="qc" /> + <spanspec namest="cr" nameend="cb" spanname="chrom" /> + <spanspec namest="qy" nameend="qc" spanname="quant" /> + <spanspec namest="lum" nameend="qc" spanname="spam" /> + <thead> + <row> + <entry morerows="1">Identifier</entry> + <entry morerows="1">Value</entry> + <entry morerows="1">Description</entry> + <entry spanname="chrom">Chromaticities<footnote> + <para>The coordinates of the color primaries are +given in the CIE system (1931)</para> + </footnote></entry> + <entry morerows="1">White Point</entry> + <entry morerows="1">Gamma Correction</entry> + <entry morerows="1">Luminance E'<subscript>Y</subscript></entry> + <entry spanname="quant">Quantization</entry> + </row> + <row> + <entry>Red</entry> + <entry>Green</entry> + <entry>Blue</entry> + <entry>Y'</entry> + <entry>Cb, Cr</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>V4L2_COLORSPACE_SMPTE170M</constant></entry> + <entry>1</entry> + <entry>NTSC/PAL according to <xref linkend="smpte170m" />, +<xref linkend="itu601" /></entry> + <entry>x = 0.630, y = 0.340</entry> + <entry>x = 0.310, y = 0.595</entry> + <entry>x = 0.155, y = 0.070</entry> + <entry>x = 0.3127, y = 0.3290, + Illuminant D<subscript>65</subscript></entry> + <entry>E' = 4.5 I for I ≤0.018, +1.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry> + <entry>0.299 E'<subscript>R</subscript> ++ 0.587 E'<subscript>G</subscript> ++ 0.114 E'<subscript>B</subscript></entry> + <entry>219 E'<subscript>Y</subscript> + 16</entry> + <entry>224 P<subscript>B,R</subscript> + 128</entry> + </row> + <row> + <entry><constant>V4L2_COLORSPACE_SMPTE240M</constant></entry> + <entry>2</entry> + <entry>1125-Line (US) HDTV, see <xref +linkend="smpte240m" /></entry> + <entry>x = 0.630, y = 0.340</entry> + <entry>x = 0.310, y = 0.595</entry> + <entry>x = 0.155, y = 0.070</entry> + <entry>x = 0.3127, y = 0.3290, + Illuminant D<subscript>65</subscript></entry> + <entry>E' = 4 I for I ≤0.0228, +1.1115 I<superscript>0.45</superscript> - 0.1115 for 0.0228 < I</entry> + <entry>0.212 E'<subscript>R</subscript> ++ 0.701 E'<subscript>G</subscript> ++ 0.087 E'<subscript>B</subscript></entry> + <entry>219 E'<subscript>Y</subscript> + 16</entry> + <entry>224 P<subscript>B,R</subscript> + 128</entry> + </row> + <row> + <entry><constant>V4L2_COLORSPACE_REC709</constant></entry> + <entry>3</entry> + <entry>HDTV and modern devices, see <xref +linkend="itu709" /></entry> + <entry>x = 0.640, y = 0.330</entry> + <entry>x = 0.300, y = 0.600</entry> + <entry>x = 0.150, y = 0.060</entry> + <entry>x = 0.3127, y = 0.3290, + Illuminant D<subscript>65</subscript></entry> + <entry>E' = 4.5 I for I ≤0.018, +1.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry> + <entry>0.2125 E'<subscript>R</subscript> ++ 0.7154 E'<subscript>G</subscript> ++ 0.0721 E'<subscript>B</subscript></entry> + <entry>219 E'<subscript>Y</subscript> + 16</entry> + <entry>224 P<subscript>B,R</subscript> + 128</entry> + </row> + <row> + <entry><constant>V4L2_COLORSPACE_BT878</constant></entry> + <entry>4</entry> + <entry>Broken Bt878 extents<footnote> + <para>The ubiquitous Bt878 video capture chip +quantizes E'<subscript>Y</subscript> to 238 levels, yielding a range +of Y' = 16 … 253, unlike Rec. 601 Y' = 16 … +235. This is not a typo in the Bt878 documentation, it has been +implemented in silicon. The chroma extents are unclear.</para> + </footnote>, <xref linkend="itu601" /></entry> + <entry>?</entry> + <entry>?</entry> + <entry>?</entry> + <entry>?</entry> + <entry>?</entry> + <entry>0.299 E'<subscript>R</subscript> ++ 0.587 E'<subscript>G</subscript> ++ 0.114 E'<subscript>B</subscript></entry> + <entry><emphasis>237</emphasis> E'<subscript>Y</subscript> + 16</entry> + <entry>224 P<subscript>B,R</subscript> + 128 (probably)</entry> + </row> + <row> + <entry><constant>V4L2_COLORSPACE_470_SYSTEM_M</constant></entry> + <entry>5</entry> + <entry>M/NTSC<footnote> + <para>No identifier exists for M/PAL which uses +the chromaticities of M/NTSC, the remaining parameters are equal to B and +G/PAL.</para> + </footnote> according to <xref linkend="itu470" />, <xref + linkend="itu601" /></entry> + <entry>x = 0.67, y = 0.33</entry> + <entry>x = 0.21, y = 0.71</entry> + <entry>x = 0.14, y = 0.08</entry> + <entry>x = 0.310, y = 0.316, Illuminant C</entry> + <entry>?</entry> + <entry>0.299 E'<subscript>R</subscript> ++ 0.587 E'<subscript>G</subscript> ++ 0.114 E'<subscript>B</subscript></entry> + <entry>219 E'<subscript>Y</subscript> + 16</entry> + <entry>224 P<subscript>B,R</subscript> + 128</entry> + </row> + <row> + <entry><constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant></entry> + <entry>6</entry> + <entry>625-line PAL and SECAM systems according to <xref +linkend="itu470" />, <xref linkend="itu601" /></entry> + <entry>x = 0.64, y = 0.33</entry> + <entry>x = 0.29, y = 0.60</entry> + <entry>x = 0.15, y = 0.06</entry> + <entry>x = 0.313, y = 0.329, +Illuminant D<subscript>65</subscript></entry> + <entry>?</entry> + <entry>0.299 E'<subscript>R</subscript> ++ 0.587 E'<subscript>G</subscript> ++ 0.114 E'<subscript>B</subscript></entry> + <entry>219 E'<subscript>Y</subscript> + 16</entry> + <entry>224 P<subscript>B,R</subscript> + 128</entry> + </row> + <row> + <entry><constant>V4L2_COLORSPACE_JPEG</constant></entry> + <entry>7</entry> + <entry>JPEG Y'CbCr, see <xref linkend="jfif" />, <xref linkend="itu601" /></entry> + <entry>?</entry> + <entry>?</entry> + <entry>?</entry> + <entry>?</entry> + <entry>?</entry> + <entry>0.299 E'<subscript>R</subscript> ++ 0.587 E'<subscript>G</subscript> ++ 0.114 E'<subscript>B</subscript></entry> + <entry>256 E'<subscript>Y</subscript> + 16<footnote> + <para>Note JFIF quantizes +Y'P<subscript>B</subscript>P<subscript>R</subscript> in range [0;+1] and +[-0.5;+0.5] to <emphasis>257</emphasis> levels, however Y'CbCr signals +are still clamped to [0;255].</para> + </footnote></entry> + <entry>256 P<subscript>B,R</subscript> + 128</entry> + </row> + <row> + <entry><constant>V4L2_COLORSPACE_SRGB</constant></entry> + <entry>8</entry> + <entry>[?]</entry> + <entry>x = 0.640, y = 0.330</entry> + <entry>x = 0.300, y = 0.600</entry> + <entry>x = 0.150, y = 0.060</entry> + <entry>x = 0.3127, y = 0.3290, + Illuminant D<subscript>65</subscript></entry> + <entry>E' = 4.5 I for I ≤0.018, +1.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry> + <entry spanname="spam">n/a</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + + <section id="pixfmt-indexed"> + <title>Indexed Format</title> + + <para>In this format each pixel is represented by an 8 bit index +into a 256 entry ARGB palette. It is intended for <link +linkend="osd">Video Output Overlays</link> only. There are no ioctls to +access the palette, this must be done with ioctls of the Linux framebuffer API.</para> + + <table pgwide="0" frame="none"> + <title>Indexed Image Format</title> + <tgroup cols="37" align="center"> + <colspec colname="id" align="left" /> + <colspec colname="fourcc" /> + <colspec colname="bit" /> + + <colspec colnum="4" colname="b07" align="center" /> + <colspec colnum="5" colname="b06" align="center" /> + <colspec colnum="6" colname="b05" align="center" /> + <colspec colnum="7" colname="b04" align="center" /> + <colspec colnum="8" colname="b03" align="center" /> + <colspec colnum="9" colname="b02" align="center" /> + <colspec colnum="10" colname="b01" align="center" /> + <colspec colnum="11" colname="b00" align="center" /> + + <spanspec namest="b07" nameend="b00" spanname="b0" /> + <spanspec namest="b17" nameend="b10" spanname="b1" /> + <spanspec namest="b27" nameend="b20" spanname="b2" /> + <spanspec namest="b37" nameend="b30" spanname="b3" /> + <thead> + <row> + <entry>Identifier</entry> + <entry>Code</entry> + <entry> </entry> + <entry spanname="b0">Byte 0</entry> + </row> + <row> + <entry> </entry> + <entry> </entry> + <entry>Bit</entry> + <entry>7</entry> + <entry>6</entry> + <entry>5</entry> + <entry>4</entry> + <entry>3</entry> + <entry>2</entry> + <entry>1</entry> + <entry>0</entry> + </row> + </thead> + <tbody valign="top"> + <row id="V4L2-PIX-FMT-PAL8"> + <entry><constant>V4L2_PIX_FMT_PAL8</constant></entry> + <entry>'PAL8'</entry> + <entry></entry> + <entry>i<subscript>7</subscript></entry> + <entry>i<subscript>6</subscript></entry> + <entry>i<subscript>5</subscript></entry> + <entry>i<subscript>4</subscript></entry> + <entry>i<subscript>3</subscript></entry> + <entry>i<subscript>2</subscript></entry> + <entry>i<subscript>1</subscript></entry> + <entry>i<subscript>0</subscript></entry> + </row> + </tbody> + </tgroup> + </table> + </section> + + <section id="pixfmt-rgb"> + <title>RGB Formats</title> + + &sub-packed-rgb; + &sub-sbggr8; + &sub-sgbrg8; + &sub-sgrbg8; + &sub-sbggr16; + </section> + + <section id="yuv-formats"> + <title>YUV Formats</title> + + <para>YUV is the format native to TV broadcast and composite video +signals. It separates the brightness information (Y) from the color +information (U and V or Cb and Cr). The color information consists of +red and blue <emphasis>color difference</emphasis> signals, this way +the green component can be reconstructed by subtracting from the +brightness component. See <xref linkend="colorspaces" /> for conversion +examples. YUV was chosen because early television would only transmit +brightness information. To add color in a way compatible with existing +receivers a new signal carrier was added to transmit the color +difference signals. Secondary in the YUV format the U and V components +usually have lower resolution than the Y component. This is an analog +video compression technique taking advantage of a property of the +human visual system, being more sensitive to brightness +information.</para> + + &sub-packed-yuv; + &sub-grey; + &sub-y16; + &sub-yuyv; + &sub-uyvy; + &sub-yvyu; + &sub-vyuy; + &sub-y41p; + &sub-yuv420; + &sub-yuv410; + &sub-yuv422p; + &sub-yuv411p; + &sub-nv12; + &sub-nv16; + </section> + + <section> + <title>Compressed Formats</title> + + <table pgwide="1" frame="none" id="compressed-formats"> + <title>Compressed Image Formats</title> + <tgroup cols="3" align="left"> + &cs-def; + <thead> + <row> + <entry>Identifier</entry> + <entry>Code</entry> + <entry>Details</entry> + </row> + </thead> + <tbody valign="top"> + <row id="V4L2-PIX-FMT-JPEG"> + <entry><constant>V4L2_PIX_FMT_JPEG</constant></entry> + <entry>'JPEG'</entry> + <entry>TBD. See also &VIDIOC-G-JPEGCOMP;, + &VIDIOC-S-JPEGCOMP;.</entry> + </row> + <row id="V4L2-PIX-FMT-MPEG"> + <entry><constant>V4L2_PIX_FMT_MPEG</constant></entry> + <entry>'MPEG'</entry> + <entry>MPEG stream. The actual format is determined by +extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see +<xref linkend="mpeg-control-id" />.</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + + <section id="pixfmt-reserved"> + <title>Reserved Format Identifiers</title> + + <para>These formats are not defined by this specification, they +are just listed for reference and to avoid naming conflicts. If you +want to register your own format, send an e-mail to the linux-media mailing +list &v4l-ml; for inclusion in the <filename>videodev2.h</filename> +file. If you want to share your format with other developers add a +link to your documentation and send a copy to the linux-media mailing list +for inclusion in this section. If you think your format should be listed +in a standard format section please make a proposal on the linux-media mailing +list.</para> + + <table pgwide="1" frame="none" id="reserved-formats"> + <title>Reserved Image Formats</title> + <tgroup cols="3" align="left"> + &cs-def; + <thead> + <row> + <entry>Identifier</entry> + <entry>Code</entry> + <entry>Details</entry> + </row> + </thead> + <tbody valign="top"> + <row id="V4L2-PIX-FMT-DV"> + <entry><constant>V4L2_PIX_FMT_DV</constant></entry> + <entry>'dvsd'</entry> + <entry>unknown</entry> + </row> + <row id="V4L2-PIX-FMT-ET61X251"> + <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry> + <entry>'E625'</entry> + <entry>Compressed format of the ET61X251 driver.</entry> + </row> + <row id="V4L2-PIX-FMT-HI240"> + <entry><constant>V4L2_PIX_FMT_HI240</constant></entry> + <entry>'HI24'</entry> + <entry><para>8 bit RGB format used by the BTTV driver.</para></entry> + </row> + <row id="V4L2-PIX-FMT-HM12"> + <entry><constant>V4L2_PIX_FMT_HM12</constant></entry> + <entry>'HM12'</entry> + <entry><para>YUV 4:2:0 format used by the +IVTV driver, <ulink url="http://www.ivtvdriver.org/"> +http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the +kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename> +</para></entry> + </row> + <row id="V4L2-PIX-FMT-SPCA501"> + <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry> + <entry>'S501'</entry> + <entry>YUYV per line used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-SPCA505"> + <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry> + <entry>'S505'</entry> + <entry>YYUV per line used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-SPCA508"> + <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry> + <entry>'S508'</entry> + <entry>YUVY per line used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-SPCA561"> + <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry> + <entry>'S561'</entry> + <entry>Compressed GBRG Bayer format used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-SGRBG10"> + <entry><constant>V4L2_PIX_FMT_SGRBG10</constant></entry> + <entry>'DA10'</entry> + <entry>10 bit raw Bayer, expanded to 16 bits.</entry> + </row> + <row id="V4L2-PIX-FMT-SGRBG10DPCM8"> + <entry><constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant></entry> + <entry>'DB10'</entry> + <entry>10 bit raw Bayer DPCM compressed to 8 bits.</entry> + </row> + <row id="V4L2-PIX-FMT-PAC207"> + <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry> + <entry>'P207'</entry> + <entry>Compressed BGGR Bayer format used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-MR97310A"> + <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry> + <entry>'M310'</entry> + <entry>Compressed BGGR Bayer format used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-OV511"> + <entry><constant>V4L2_PIX_FMT_OV511</constant></entry> + <entry>'O511'</entry> + <entry>OV511 JPEG format used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-OV518"> + <entry><constant>V4L2_PIX_FMT_OV518</constant></entry> + <entry>'O518'</entry> + <entry>OV518 JPEG format used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-PJPG"> + <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry> + <entry>'PJPG'</entry> + <entry>Pixart 73xx JPEG format used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-SQ905C"> + <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry> + <entry>'905C'</entry> + <entry>Compressed RGGB bayer format used by the gspca driver.</entry> + </row> + <row id="V4L2-PIX-FMT-MJPEG"> + <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry> + <entry>'MJPG'</entry> + <entry>Compressed format used by the Zoran driver</entry> + </row> + <row id="V4L2-PIX-FMT-PWC1"> + <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry> + <entry>'PWC1'</entry> + <entry>Compressed format of the PWC driver.</entry> + </row> + <row id="V4L2-PIX-FMT-PWC2"> + <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry> + <entry>'PWC2'</entry> + <entry>Compressed format of the PWC driver.</entry> + </row> + <row id="V4L2-PIX-FMT-SN9C10X"> + <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry> + <entry>'S910'</entry> + <entry>Compressed format of the SN9C102 driver.</entry> + </row> + <row id="V4L2-PIX-FMT-SN9C20X-I420"> + <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry> + <entry>'S920'</entry> + <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry> + </row> + <row id="V4L2-PIX-FMT-WNVA"> + <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry> + <entry>'WNVA'</entry> + <entry><para>Used by the Winnov Videum driver, <ulink +url="http://www.thedirks.org/winnov/"> +http://www.thedirks.org/winnov/</ulink></para></entry> + </row> + <row id="V4L2-PIX-FMT-YYUV"> + <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry> + <entry>'YYUV'</entry> + <entry>unknown</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + + <!-- +Local Variables: +mode: sgml +sgml-parent-document: "v4l2.sgml" +indent-tabs-mode: nil +End: + --> |