1.16. V4L2 DV Timings functions¶
-
bool
v4l2_valid_dv_timings
(const struct v4l2_dv_timings * t, const struct v4l2_dv_timings_cap * cap, v4l2_check_dv_timings_fnc fnc, void * fnc_handle)¶ are these timings valid?
Parameters
const struct v4l2_dv_timings * t
- the v4l2_dv_timings struct.
const struct v4l2_dv_timings_cap * cap
- the v4l2_dv_timings_cap capabilities.
v4l2_check_dv_timings_fnc fnc
- callback to check if this timing is OK. May be NULL.
void * fnc_handle
- a handle that is passed on to fnc.
Description
Returns true if the given dv_timings struct is supported by the hardware capabilities and the callback function (if non-NULL), returns false otherwise.
-
int
v4l2_enum_dv_timings_cap
(struct v4l2_enum_dv_timings * t, const struct v4l2_dv_timings_cap * cap, v4l2_check_dv_timings_fnc fnc, void * fnc_handle)¶ Helper function to enumerate possible DV timings based on capabilities
Parameters
struct v4l2_enum_dv_timings * t
- the v4l2_enum_dv_timings struct.
const struct v4l2_dv_timings_cap * cap
- the v4l2_dv_timings_cap capabilities.
v4l2_check_dv_timings_fnc fnc
- callback to check if this timing is OK. May be NULL.
void * fnc_handle
- a handle that is passed on to fnc.
Description
This enumerates dv_timings using the full list of possible CEA-861 and DMT timings, filtering out any timings that are not supported based on the hardware capabilities and the callback function (if non-NULL).
If a valid timing for the given index is found, it will fill in t and return 0, otherwise it returns -EINVAL.
-
bool
v4l2_find_dv_timings_cap
(struct v4l2_dv_timings * t, const struct v4l2_dv_timings_cap * cap, unsigned pclock_delta, v4l2_check_dv_timings_fnc fnc, void * fnc_handle)¶ Find the closest timings struct
Parameters
struct v4l2_dv_timings * t
- the v4l2_enum_dv_timings struct.
const struct v4l2_dv_timings_cap * cap
- the v4l2_dv_timings_cap capabilities.
unsigned pclock_delta
- maximum delta between t->pixelclock and the timing struct under consideration.
v4l2_check_dv_timings_fnc fnc
- callback to check if a given timings struct is OK. May be NULL.
void * fnc_handle
- a handle that is passed on to fnc.
Description
This function tries to map the given timings to an entry in the full list of possible CEA-861 and DMT timings, filtering out any timings that are not supported based on the hardware capabilities and the callback function (if non-NULL).
On success it will fill in t with the found timings and it returns true. On failure it will return false.
-
bool
v4l2_match_dv_timings
(const struct v4l2_dv_timings * measured, const struct v4l2_dv_timings * standard, unsigned pclock_delta, bool match_reduced_fps)¶ do two timings match?
Parameters
const struct v4l2_dv_timings * measured
- the measured timings data.
const struct v4l2_dv_timings * standard
- the timings according to the standard.
unsigned pclock_delta
- maximum delta in Hz between standard->pixelclock and the measured timings.
bool match_reduced_fps
- if true, then fail if V4L2_DV_FL_REDUCED_FPS does not match.
Description
Returns true if the two timings match, returns false otherwise.
-
void
v4l2_print_dv_timings
(const char * dev_prefix, const char * prefix, const struct v4l2_dv_timings * t, bool detailed)¶ log the contents of a dv_timings struct
Parameters
const char * dev_prefix
- device prefix for each log line.
const char * prefix
- additional prefix for each log line, may be NULL.
const struct v4l2_dv_timings * t
- the timings data.
bool detailed
- if true, give a detailed log.
-
bool
v4l2_detect_cvt
(unsigned frame_height, unsigned hfreq, unsigned vsync, unsigned active_width, u32 polarities, bool interlaced, struct v4l2_dv_timings * fmt)¶ detect if the given timings follow the CVT standard
Parameters
unsigned frame_height
- the total height of the frame (including blanking) in lines.
unsigned hfreq
- the horizontal frequency in Hz.
unsigned vsync
- the height of the vertical sync in lines.
unsigned active_width
- active width of image (does not include blanking). This information is needed only in case of version 2 of reduced blanking. In other cases, this parameter does not have any effect on timings.
u32 polarities
- the horizontal and vertical polarities (same as struct v4l2_bt_timings polarities).
bool interlaced
- if this flag is true, it indicates interlaced format
struct v4l2_dv_timings * fmt
- the resulting timings.
Description
This function will attempt to detect if the given values correspond to a valid CVT format. If so, then it will return true, and fmt will be filled in with the found CVT timings.
-
bool
v4l2_detect_gtf
(unsigned frame_height, unsigned hfreq, unsigned vsync, u32 polarities, bool interlaced, struct v4l2_fract aspect, struct v4l2_dv_timings * fmt)¶ detect if the given timings follow the GTF standard
Parameters
unsigned frame_height
- the total height of the frame (including blanking) in lines.
unsigned hfreq
- the horizontal frequency in Hz.
unsigned vsync
- the height of the vertical sync in lines.
u32 polarities
- the horizontal and vertical polarities (same as struct v4l2_bt_timings polarities).
bool interlaced
- if this flag is true, it indicates interlaced format
struct v4l2_fract aspect
- preferred aspect ratio. GTF has no method of determining the aspect ratio in order to derive the image width from the image height, so it has to be passed explicitly. Usually the native screen aspect ratio is used for this. If it is not filled in correctly, then 16:9 will be assumed.
struct v4l2_dv_timings * fmt
- the resulting timings.
Description
This function will attempt to detect if the given values correspond to a valid GTF format. If so, then it will return true, and fmt will be filled in with the found GTF timings.
-
struct v4l2_fract
v4l2_calc_aspect_ratio
(u8 hor_landscape, u8 vert_portrait)¶ calculate the aspect ratio based on bytes 0x15 and 0x16 from the EDID.
Parameters
u8 hor_landscape
- byte 0x15 from the EDID.
u8 vert_portrait
- byte 0x16 from the EDID.
Description
Determines the aspect ratio from the EDID. See VESA Enhanced EDID standard, release A, rev 2, section 3.6.2: “Horizontal and Vertical Screen Size or Aspect Ratio”