diff options
Diffstat (limited to 'Documentation/media/uapi/v4l/dev-raw-vbi.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/dev-raw-vbi.rst | 267 |
1 files changed, 110 insertions, 157 deletions
diff --git a/Documentation/media/uapi/v4l/dev-raw-vbi.rst b/Documentation/media/uapi/v4l/dev-raw-vbi.rst index d5a4b3530b69..b82d837e4ff1 100644 --- a/Documentation/media/uapi/v4l/dev-raw-vbi.rst +++ b/Documentation/media/uapi/v4l/dev-raw-vbi.rst @@ -39,7 +39,7 @@ Querying Capabilities Devices supporting the raw VBI capturing or output API set the ``V4L2_CAP_VBI_CAPTURE`` or ``V4L2_CAP_VBI_OUTPUT`` flags, respectively, in the ``capabilities`` field of struct -:ref:`v4l2_capability <v4l2-capability>` returned by the +:c:type:`v4l2_capability` returned by the :ref:`VIDIOC_QUERYCAP` ioctl. At least one of the read/write, streaming or asynchronous I/O methods must be supported. VBI devices may or may not have a tuner or modulator. @@ -69,16 +69,16 @@ always ensure they really get what they want, requesting reasonable parameters and then checking if the actual parameters are suitable. To query the current raw VBI capture parameters applications set the -``type`` field of a struct :ref:`v4l2_format <v4l2-format>` to +``type`` field of a struct :c:type:`v4l2_format` to ``V4L2_BUF_TYPE_VBI_CAPTURE`` or ``V4L2_BUF_TYPE_VBI_OUTPUT``, and call the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl with a pointer to this structure. Drivers fill the struct -:ref:`v4l2_vbi_format <v4l2-vbi-format>` ``vbi`` member of the +:c:type:`v4l2_vbi_format` ``vbi`` member of the ``fmt`` union. To request different parameters applications set the ``type`` field of a -struct :ref:`v4l2_format <v4l2-format>` as above and initialize all -fields of the struct :ref:`v4l2_vbi_format <v4l2-vbi-format>` +struct :c:type:`v4l2_format` as above and initialize all +fields of the struct :c:type:`v4l2_vbi_format` ``vbi`` member of the ``fmt`` union, or better just modify the results of :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`, and call the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with a pointer to this structure. Drivers return an ``EINVAL`` error @@ -99,131 +99,91 @@ VBI devices must implement both the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does. :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is optional. +.. tabularcolumns:: |p{2.4cm}|p{4.4cm}|p{10.7cm}| -.. _v4l2-vbi-format: +.. c:type:: v4l2_vbi_format + +.. cssclass:: longtable .. flat-table:: struct v4l2_vbi_format :header-rows: 0 :stub-columns: 0 :widths: 1 1 2 - - - .. row 1 - - - __u32 - - - ``sampling_rate`` - - - Samples per second, i. e. unit 1 Hz. - - - .. row 2 - - - __u32 - - - ``offset`` - - - Horizontal offset of the VBI image, relative to the leading edge - of the line synchronization pulse and counted in samples: The - first sample in the VBI image will be located ``offset`` / - ``sampling_rate`` seconds following the leading edge. See also - :ref:`vbi-hsync`. - - - .. row 3 - - - __u32 - - - ``samples_per_line`` - - - - - - .. row 4 - - - __u32 - - - ``sample_format`` - - - Defines the sample format as in :ref:`pixfmt`, a - four-character-code. [#f2]_ Usually this is ``V4L2_PIX_FMT_GREY``, - i. e. each sample consists of 8 bits with lower values oriented - towards the black level. Do not assume any other correlation of - values with the signal level. For example, the MSB does not - necessarily indicate if the signal is 'high' or 'low' because 128 - may not be the mean value of the signal. Drivers shall not convert - the sample format by software. - - - .. row 5 - - - __u32 - - - ``start``\ [#f2]_ - - - This is the scanning system line number associated with the first - line of the VBI image, of the first and the second field - respectively. See :ref:`vbi-525` and :ref:`vbi-625` for valid - values. The ``V4L2_VBI_ITU_525_F1_START``, - ``V4L2_VBI_ITU_525_F2_START``, ``V4L2_VBI_ITU_625_F1_START`` and - ``V4L2_VBI_ITU_625_F2_START`` defines give the start line numbers - for each field for each 525 or 625 line format as a convenience. - Don't forget that ITU line numbering starts at 1, not 0. VBI input - drivers can return start values 0 if the hardware cannot reliable - identify scanning lines, VBI acquisition may not require this - information. - - - .. row 6 - - - __u32 - - - ``count``\ [#f2]_ - - - The number of lines in the first and second field image, - respectively. - - - .. row 7 - - - :cspan:`2` - - Drivers should be as flexibility as possible. For example, it may - be possible to extend or move the VBI capture window down to the - picture area, implementing a 'full field mode' to capture data - service transmissions embedded in the picture. - - An application can set the first or second ``count`` value to zero - if no data is required from the respective field; ``count``\ [1] - if the scanning system is progressive, i. e. not interlaced. The - corresponding start value shall be ignored by the application and - driver. Anyway, drivers may not support single field capturing and - return both count values non-zero. - - Both ``count`` values set to zero, or line numbers outside the - bounds depicted in :ref:`vbi-525` and :ref:`vbi-625`, or a - field image covering lines of two fields, are invalid and shall - not be returned by the driver. - - To initialize the ``start`` and ``count`` fields, applications - must first determine the current video standard selection. The - :ref:`v4l2_std_id <v4l2-std-id>` or the ``framelines`` field - of struct :ref:`v4l2_standard <v4l2-standard>` can be evaluated - for this purpose. - - - .. row 8 - - - __u32 - - - ``flags`` - - - See :ref:`vbifmt-flags` below. Currently only drivers set flags, - applications must set this field to zero. - - - .. row 9 - - - __u32 - - - ``reserved``\ [#f2]_ - - - This array is reserved for future extensions. Drivers and - applications must set it to zero. - - + * - __u32 + - ``sampling_rate`` + - Samples per second, i. e. unit 1 Hz. + * - __u32 + - ``offset`` + - Horizontal offset of the VBI image, relative to the leading edge + of the line synchronization pulse and counted in samples: The + first sample in the VBI image will be located ``offset`` / + ``sampling_rate`` seconds following the leading edge. See also + :ref:`vbi-hsync`. + * - __u32 + - ``samples_per_line`` + - + * - __u32 + - ``sample_format`` + - Defines the sample format as in :ref:`pixfmt`, a + four-character-code. [#f2]_ Usually this is ``V4L2_PIX_FMT_GREY``, + i. e. each sample consists of 8 bits with lower values oriented + towards the black level. Do not assume any other correlation of + values with the signal level. For example, the MSB does not + necessarily indicate if the signal is 'high' or 'low' because 128 + may not be the mean value of the signal. Drivers shall not convert + the sample format by software. + * - __u32 + - ``start``\ [#f2]_ + - This is the scanning system line number associated with the first + line of the VBI image, of the first and the second field + respectively. See :ref:`vbi-525` and :ref:`vbi-625` for valid + values. The ``V4L2_VBI_ITU_525_F1_START``, + ``V4L2_VBI_ITU_525_F2_START``, ``V4L2_VBI_ITU_625_F1_START`` and + ``V4L2_VBI_ITU_625_F2_START`` defines give the start line numbers + for each field for each 525 or 625 line format as a convenience. + Don't forget that ITU line numbering starts at 1, not 0. VBI input + drivers can return start values 0 if the hardware cannot reliable + identify scanning lines, VBI acquisition may not require this + information. + * - __u32 + - ``count``\ [#f2]_ + - The number of lines in the first and second field image, + respectively. + * - :cspan:`2` + + Drivers should be as flexibility as possible. For example, it may + be possible to extend or move the VBI capture window down to the + picture area, implementing a 'full field mode' to capture data + service transmissions embedded in the picture. + + An application can set the first or second ``count`` value to zero + if no data is required from the respective field; ``count``\ [1] + if the scanning system is progressive, i. e. not interlaced. The + corresponding start value shall be ignored by the application and + driver. Anyway, drivers may not support single field capturing and + return both count values non-zero. + + Both ``count`` values set to zero, or line numbers are outside the + bounds depicted\ [#f4]_, or a field image covering lines of two + fields, are invalid and shall not be returned by the driver. + + To initialize the ``start`` and ``count`` fields, applications + must first determine the current video standard selection. The + :ref:`v4l2_std_id <v4l2-std-id>` or the ``framelines`` field + of struct :c:type:`v4l2_standard` can be evaluated + for this purpose. + * - __u32 + - ``flags`` + - See :ref:`vbifmt-flags` below. Currently only drivers set flags, + applications must set this field to zero. + * - __u32 + - ``reserved``\ [#f2]_ + - This array is reserved for future extensions. Drivers and + applications must set it to zero. + + +.. tabularcolumns:: |p{4.0cm}|p{1.5cm}|p{12.0cm}| .. _vbifmt-flags: @@ -232,40 +192,30 @@ and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does :stub-columns: 0 :widths: 3 1 4 - - - .. row 1 - - - ``V4L2_VBI_UNSYNC`` - - - 0x0001 - - - This flag indicates hardware which does not properly distinguish - between fields. Normally the VBI image stores the first field - (lower scanning line numbers) first in memory. This may be a top - or bottom field depending on the video standard. When this flag is - set the first or second field may be stored first, however the - fields are still in correct temporal order with the older field - first in memory. [#f3]_ - - - .. row 2 - - - ``V4L2_VBI_INTERLACED`` - - - 0x0002 - - - By default the two field images will be passed sequentially; all - lines of the first field followed by all lines of the second field - (compare :ref:`field-order` ``V4L2_FIELD_SEQ_TB`` and - ``V4L2_FIELD_SEQ_BT``, whether the top or bottom field is first in - memory depends on the video standard). When this flag is set, the - two fields are interlaced (cf. ``V4L2_FIELD_INTERLACED``). The - first line of the first field followed by the first line of the - second field, then the two second lines, and so on. Such a layout - may be necessary when the hardware has been programmed to capture - or output interlaced video images and is unable to separate the - fields for VBI capturing at the same time. For simplicity setting - this flag implies that both ``count`` values are equal and - non-zero. + * - ``V4L2_VBI_UNSYNC`` + - 0x0001 + - This flag indicates hardware which does not properly distinguish + between fields. Normally the VBI image stores the first field + (lower scanning line numbers) first in memory. This may be a top + or bottom field depending on the video standard. When this flag is + set the first or second field may be stored first, however the + fields are still in correct temporal order with the older field + first in memory. [#f3]_ + * - ``V4L2_VBI_INTERLACED`` + - 0x0002 + - By default the two field images will be passed sequentially; all + lines of the first field followed by all lines of the second field + (compare :ref:`field-order` ``V4L2_FIELD_SEQ_TB`` and + ``V4L2_FIELD_SEQ_BT``, whether the top or bottom field is first in + memory depends on the video standard). When this flag is set, the + two fields are interlaced (cf. ``V4L2_FIELD_INTERLACED``). The + first line of the first field followed by the first line of the + second field, then the two second lines, and so on. Such a layout + may be necessary when the hardware has been programmed to capture + or output interlaced video images and is unable to separate the + fields for VBI capturing at the same time. For simplicity setting + this flag implies that both ``count`` values are equal and + non-zero. @@ -348,3 +298,6 @@ another process. Most VBI services transmit on both fields, but some have different semantics depending on the field number. These cannot be reliable decoded or encoded when ``V4L2_VBI_UNSYNC`` is set. + +.. [#f4] + The valid values ar shown at :ref:`vbi-525` and :ref:`vbi-625`. |