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Diffstat (limited to 'Documentation/media/uapi/v4l/pixfmt-v4l2.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/pixfmt-v4l2.rst | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst index 71eebfc6d853..a8321c348bf8 100644 --- a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst @@ -39,12 +39,17 @@ Single-planar format structure to a multiple of the scale factor of any smaller planes. For example when the image format is YUV 4:2:0, ``width`` and ``height`` must be multiples of two. + + For compressed formats that contain the resolution information encoded + inside the stream, when fed to a stateful mem2mem decoder, the fields + may be zero to rely on the decoder to detect the right values. For more + details see :ref:`decoder` and format descriptions. * - __u32 - ``pixelformat`` - The pixel format or type of compression, set by the application. This is a little endian :ref:`four character code <v4l2-fourcc>`. V4L2 defines standard - RGB formats in :ref:`rgb-formats`, YUV formats in + RGB formats in :ref:`pixfmt-rgb`, YUV formats in :ref:`yuv-formats`, and reserved codes in :ref:`reserved-formats` * - __u32 @@ -89,7 +94,18 @@ Single-planar format structure - Size in bytes of the buffer to hold a complete image, set by the driver. Usually this is ``bytesperline`` times ``height``. When the image consists of variable length compressed data this is the - maximum number of bytes required to hold an image. + number of bytes required by the codec to support the worst-case + compression scenario. + + The driver will set the value for uncompressed images. + + Clients are allowed to set the sizeimage field for variable length + compressed data flagged with ``V4L2_FMT_FLAG_COMPRESSED`` at + :ref:`VIDIOC_ENUM_FMT`, but the driver may ignore it and set the + value itself, or it may modify the provided value based on + alignment requirements or minimum/maximum size requirements. + If the client wants to leave this to the driver, then it should + set sizeimage to 0. * - __u32 - ``colorspace`` - Image colorspace, from enum :c:type:`v4l2_colorspace`. |