From 29fa0eedd4703b0c7c93738faf28ac9d6f930224 Mon Sep 17 00:00:00 2001 From: Sylwester Nawrocki Date: Fri, 20 Jan 2012 15:38:50 -0300 Subject: [PATCH] [media] V4L: Add JPEG compression control class documentation Add DocBook entries for the JPEG control class. Signed-off-by: Sylwester Nawrocki Signed-off-by: Kyungmin Park Signed-off-by: Mauro Carvalho Chehab --- Documentation/DocBook/media/v4l/biblio.xml | 20 +++ Documentation/DocBook/media/v4l/compat.xml | 10 ++ Documentation/DocBook/media/v4l/controls.xml | 161 ++++++++++++++++++ Documentation/DocBook/media/v4l/v4l2.xml | 9 + .../DocBook/media/v4l/vidioc-g-jpegcomp.xml | 16 +- 5 files changed, 214 insertions(+), 2 deletions(-) diff --git a/Documentation/DocBook/media/v4l/biblio.xml b/Documentation/DocBook/media/v4l/biblio.xml index cea6fd3ed428..7dc65c592a87 100644 --- a/Documentation/DocBook/media/v4l/biblio.xml +++ b/Documentation/DocBook/media/v4l/biblio.xml @@ -128,6 +128,26 @@ url="http://www.ijg.org">http://www.ijg.org) Version 1.02 + + ITU-T.81 + + International Telecommunication Union +(http://www.itu.int) + + ITU-T Recommendation T.81 +"Information Technology — Digital Compression and Coding of Continous-Tone +Still Images — Requirements and Guidelines" + + + + W3C JPEG JFIF + + The World Wide Web Consortium (http://www.w3.org) + + JPEG JFIF + + SMPTE 12M diff --git a/Documentation/DocBook/media/v4l/compat.xml b/Documentation/DocBook/media/v4l/compat.xml index c93298ff3279..dd958b5a34e6 100644 --- a/Documentation/DocBook/media/v4l/compat.xml +++ b/Documentation/DocBook/media/v4l/compat.xml @@ -2400,6 +2400,16 @@ details. +
+ V4L2 in Linux 3.4 + + + Added JPEG compression control + class. + + +
+
Relation of V4L2 to other Linux multimedia APIs diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml index 3f3d2e2d424e..b84f25e9cc87 100644 --- a/Documentation/DocBook/media/v4l/controls.xml +++ b/Documentation/DocBook/media/v4l/controls.xml @@ -3436,6 +3436,167 @@ interface and may change in the future. +
+ +
+ JPEG Control Reference + The JPEG class includes controls for common features of JPEG + encoders and decoders. Currently it includes features for codecs + implementing progressive baseline DCT compression process with + Huffman entrophy coding. + + JPEG Control IDs + + + + + + + + + + + ID + Type + Description + + + + + + V4L2_CID_JPEG_CLASS  + class + The JPEG class descriptor. Calling + &VIDIOC-QUERYCTRL; for this control will return a description of this + control class. + + + + + V4L2_CID_JPEG_CHROMA_SUBSAMPLING + menu + + + The chroma subsampling factors describe how + each component of an input image is sampled, in respect to maximum + sample rate in each spatial dimension. See , + clause A.1.1. for more details. The + V4L2_CID_JPEG_CHROMA_SUBSAMPLING control determines how + Cb and Cr components are downsampled after coverting an input image + from RGB to Y'CbCr color space. + + + + + + + V4L2_JPEG_CHROMA_SUBSAMPLING_444 + No chroma subsampling, each pixel has + Y, Cr and Cb values. + + + V4L2_JPEG_CHROMA_SUBSAMPLING_422 + Horizontally subsample Cr, Cb components + by a factor of 2. + + + V4L2_JPEG_CHROMA_SUBSAMPLING_420 + Subsample Cr, Cb components horizontally + and vertically by 2. + + + V4L2_JPEG_CHROMA_SUBSAMPLING_411 + Horizontally subsample Cr, Cb components + by a factor of 4. + + + V4L2_JPEG_CHROMA_SUBSAMPLING_410 + Subsample Cr, Cb components horizontally + by 4 and vertically by 2. + + + V4L2_JPEG_CHROMA_SUBSAMPLING_GRAY + Use only luminance component. + + + + + + V4L2_CID_JPEG_RESTART_INTERVAL + integer + + + The restart interval determines an interval of inserting RSTm + markers (m = 0..7). The purpose of these markers is to additionally + reinitialize the encoder process, in order to process blocks of + an image independently. + For the lossy compression processes the restart interval unit is + MCU (Minimum Coded Unit) and its value is contained in DRI + (Define Restart Interval) marker. If + V4L2_CID_JPEG_RESTART_INTERVAL control is set to 0, + DRI and RSTm markers will not be inserted. + + + + V4L2_CID_JPEG_COMPRESION_QUALITY + integer + + + + V4L2_CID_JPEG_COMPRESION_QUALITY control + determines trade-off between image quality and size. + It provides simpler method for applications to control image quality, + without a need for direct reconfiguration of luminance and chrominance + quantization tables. + + In cases where a driver uses quantization tables configured directly + by an application, using interfaces defined elsewhere, + V4L2_CID_JPEG_COMPRESION_QUALITY control should be set + by driver to 0. + The value range of this control is driver-specific. Only + positive, non-zero values are meaningful. The recommended range + is 1 - 100, where larger values correspond to better image quality. + + + + + V4L2_CID_JPEG_ACTIVE_MARKER + bitmask + + + Specify which JPEG markers are included + in compressed stream. This control is valid only for encoders. + + + + + + + V4L2_JPEG_ACTIVE_MARKER_APP0 + Application data segment APP0. + + V4L2_JPEG_ACTIVE_MARKER_APP1 + Application data segment APP1. + + V4L2_JPEG_ACTIVE_MARKER_COM + Comment segment. + + V4L2_JPEG_ACTIVE_MARKER_DQT + Quantization tables segment. + + V4L2_JPEG_ACTIVE_MARKER_DHT + Huffman tables segment. + + + + + + + +
+ For more details about JPEG specification, refer + to , , + .
diff --git a/Documentation/DocBook/media/v4l/v4l2.xml b/Documentation/DocBook/media/v4l/v4l2.xml index dcf9e33b695f..8ae38876172e 100644 --- a/Documentation/DocBook/media/v4l/v4l2.xml +++ b/Documentation/DocBook/media/v4l/v4l2.xml @@ -127,6 +127,15 @@ structs, ioctls) must be noted in more detail in the history chapter (compat.xml), along with the possible impact on existing drivers and applications. --> + + 3.4 + 2012-01-25 + sn + Added JPEG compression + control class. + + + 3.3 2012-01-11 diff --git a/Documentation/DocBook/media/v4l/vidioc-g-jpegcomp.xml b/Documentation/DocBook/media/v4l/vidioc-g-jpegcomp.xml index 01ea24b84385..48748499c097 100644 --- a/Documentation/DocBook/media/v4l/vidioc-g-jpegcomp.xml +++ b/Documentation/DocBook/media/v4l/vidioc-g-jpegcomp.xml @@ -57,6 +57,11 @@ Description + These ioctls are deprecated. + New drivers and applications should use + JPEG class controls for image quality and JPEG markers control. + + [to do] Ronald Bultje elaborates: @@ -86,7 +91,10 @@ to add them. int quality - + Deprecated. If + V4L2_CID_JPEG_IMAGE_QUALITY control is exposed by + a driver applications should use it instead and ignore this field. + int @@ -116,7 +124,11 @@ to add them. __u32 jpeg_markers - See . + See . Deprecated. + If + V4L2_CID_JPEG_ACTIVE_MARKER control + is exposed by a driver applications should use it instead + and ignore this field. -- 2.34.1