From 43f71d93a0cb342f0c918fba3f6abb7661e40ad2 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Wed, 27 Jul 2016 06:32:31 -0300 Subject: doc-rst: Remove the media docbook Now that all media documentation was converted to Sphinx, we should get rid of the old DocBook one, as we don't want people to submit patches against the old stuff. Signed-off-by: Mauro Carvalho Chehab Acked-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- Documentation/DocBook/media/v4l/dev-raw-vbi.xml | 345 ------------------------ 1 file changed, 345 deletions(-) delete mode 100644 Documentation/DocBook/media/v4l/dev-raw-vbi.xml (limited to 'Documentation/DocBook/media/v4l/dev-raw-vbi.xml') diff --git a/Documentation/DocBook/media/v4l/dev-raw-vbi.xml b/Documentation/DocBook/media/v4l/dev-raw-vbi.xml deleted file mode 100644 index 78599bbd58f7..000000000000 --- a/Documentation/DocBook/media/v4l/dev-raw-vbi.xml +++ /dev/null @@ -1,345 +0,0 @@ - Raw VBI Data Interface - - VBI is an abbreviation of Vertical Blanking Interval, a gap -in the sequence of lines of an analog video signal. During VBI -no picture information is transmitted, allowing some time while the -electron beam of a cathode ray tube TV returns to the top of the -screen. Using an oscilloscope you will find here the vertical -synchronization pulses and short data packages ASK -modulatedASK: Amplitude-Shift Keying. A high signal -level represents a '1' bit, a low level a '0' bit. -onto the video signal. These are transmissions of services such as -Teletext or Closed Caption. - - Subject of this interface type is raw VBI data, as sampled off -a video signal, or to be added to a signal for output. -The data format is similar to uncompressed video images, a number of -lines times a number of samples per line, we call this a VBI image. - - Conventionally V4L2 VBI devices are accessed through character -device special files named /dev/vbi and -/dev/vbi0 to /dev/vbi31 with -major number 81 and minor numbers 224 to 255. -/dev/vbi is typically a symbolic link to the -preferred VBI device. This convention applies to both input and output -devices. - - To address the problems of finding related video and VBI -devices VBI capturing and output is also available as device function -under /dev/video. To capture or output raw VBI -data with these devices applications must call the &VIDIOC-S-FMT; -ioctl. Accessed as /dev/vbi, raw VBI capturing -or output is the default device function. - -
- 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 &v4l2-capability; -returned by the &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. -
- -
- Supplemental Functions - - VBI devices shall support video -input or output, tuner or -modulator, and controls ioctls -as needed. The video standard ioctls provide -information vital to program a VBI device, therefore must be -supported. -
- -
- Raw VBI Format Negotiation - - Raw VBI sampling abilities can vary, in particular the -sampling frequency. To properly interpret the data V4L2 specifies an -ioctl to query the sampling parameters. Moreover, to allow for some -flexibility applications can also suggest different parameters. - - As usual these parameters are not -reset at &func-open; time to permit Unix tool chains, programming a -device and then reading from it as if it was a plain file. Well -written V4L2 applications should 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 -&v4l2-format; to V4L2_BUF_TYPE_VBI_CAPTURE or -V4L2_BUF_TYPE_VBI_OUTPUT, and call the -&VIDIOC-G-FMT; ioctl with a pointer to this structure. Drivers fill -the &v4l2-vbi-format; vbi member of the -fmt union. - - To request different parameters applications set the -type field of a &v4l2-format; as above and -initialize all fields of the &v4l2-vbi-format; -vbi member of the -fmt union, or better just modify the -results of VIDIOC_G_FMT, and call the -&VIDIOC-S-FMT; ioctl with a pointer to this structure. Drivers return -an &EINVAL; only when the given parameters are ambiguous, otherwise -they modify the parameters according to the hardware capabilities and -return the actual parameters. When the driver allocates resources at -this point, it may return an &EBUSY; to indicate the returned -parameters are valid but the required resources are currently not -available. That may happen for instance when the video and VBI areas -to capture would overlap, or when the driver supports multiple opens -and another process already requested VBI capturing or output. Anyway, -applications must expect other resource allocation points which may -return EBUSY, at the &VIDIOC-STREAMON; ioctl -and the first read(), write() and select() call. - - VBI devices must implement both the -VIDIOC_G_FMT and -VIDIOC_S_FMT ioctl, even if -VIDIOC_S_FMT ignores all requests and always -returns default parameters as VIDIOC_G_FMT does. -VIDIOC_TRY_FMT is optional. - - - struct <structname>v4l2_vbi_format</structname> - - &cs-str; - - - __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 . - - - __u32 - samples_per_line - - - - __u32 - sample_format - Defines the sample format as in , a four-character-code. - A few devices may be unable to -sample VBI data at all but can extend the video capture window to the -VBI region. - 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[2] - 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 and - 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[2] - The number of lines in the first and second -field image, respectively. - - - 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, &ie; 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 and , 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 &v4l2-std-id; or -the framelines field of &v4l2-standard; can -be evaluated for this purpose. - - - __u32 - flags - See below. Currently -only drivers set flags, applications must set this field to -zero. - - - __u32 - reserved[2] - This array is reserved for future extensions. -Drivers and applications must set it to zero. - - - -
- - - Raw VBI Format Flags - - &cs-def; - - - 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. - 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. - - - - 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 -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. - - - -
- -
- Line synchronization - - - - - - - - - Line synchronization diagram - - -
- -
- ITU-R 525 line numbering (M/NTSC and M/PAL) - - - - - - - - - NTSC field synchronization diagram - - - (1) For the purpose of this specification field 2 -starts in line 264 and not 263.5 because half line capturing is not -supported. - - -
- -
- ITU-R 625 line numbering - - - - - - - - - PAL/SECAM field synchronization diagram - - - (1) For the purpose of this specification field 2 -starts in line 314 and not 313.5 because half line capturing is not -supported. - - -
- - Remember the VBI image format depends on the selected -video standard, therefore the application must choose a new standard or -query the current standard first. Attempts to read or write data ahead -of format negotiation, or after switching the video standard which may -invalidate the negotiated VBI parameters, should be refused by the -driver. A format change during active I/O is not permitted. -
- -
- Reading and writing VBI images - - To assure synchronization with the field number and easier -implementation, the smallest unit of data passed at a time is one -frame, consisting of two fields of VBI images immediately following in -memory. - - The total size of a frame computes as follows: - - -(count[0] + count[1]) * -samples_per_line * sample size in bytes - - The sample size is most likely always one byte, -applications must check the sample_format -field though, to function properly with other drivers. - - A VBI device may support read/write and/or streaming (memory mapping or user pointer) I/O. The latter bears the -possibility of synchronizing video and -VBI data by using buffer timestamps. - - Remember the &VIDIOC-STREAMON; ioctl and the first read(), -write() and select() call can be resource allocation points returning -an &EBUSY; if the required hardware resources are temporarily -unavailable, for example the device is already in use by another -process. -
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