Raw VBI decoder

Converting raw VBI samples to bits and bytes. More...

Data Structures
struct	vbi_bit_slicer
	Bit slicer context. More...
struct	vbi_raw_decoder
	Raw vbi decoder context. More...
Typedefs
typedef struct vbi_bit_slicer	vbi_bit_slicer
	Bit slicer context.
typedef struct vbi_raw_decoder	vbi_raw_decoder
	Raw vbi decoder context.
Enumerations
enum	vbi_pixfmt {   VBI_PIXFMT_YUV420 = 1,   VBI_PIXFMT_YUYV,   VBI_PIXFMT_YVYU,   VBI_PIXFMT_UYVY,   VBI_PIXFMT_VYUY,   VBI_PIXFMT_PAL8,   VBI_PIXFMT_RGBA32_LE = 32,   VBI_PIXFMT_RGBA32_BE,   VBI_PIXFMT_BGRA32_LE,   VBI_PIXFMT_BGRA32_BE,   VBI_PIXFMT_ABGR32_BE = 32,   VBI_PIXFMT_ABGR32_LE,   VBI_PIXFMT_ARGB32_BE,   VBI_PIXFMT_ARGB32_LE,   VBI_PIXFMT_RGB24,   VBI_PIXFMT_BGR24,   VBI_PIXFMT_RGB16_LE,   VBI_PIXFMT_RGB16_BE,   VBI_PIXFMT_BGR16_LE,   VBI_PIXFMT_BGR16_BE,   VBI_PIXFMT_RGBA15_LE,   VBI_PIXFMT_RGBA15_BE,   VBI_PIXFMT_BGRA15_LE,   VBI_PIXFMT_BGRA15_BE,   VBI_PIXFMT_ARGB15_LE,   VBI_PIXFMT_ARGB15_BE,   VBI_PIXFMT_ABGR15_LE,   VBI_PIXFMT_ABGR15_BE }
	Image format used as source to vbi_bit_slice() and vbi_raw_decode(). More...
enum	vbi_modulation {   VBI_MODULATION_NRZ_LSB,   VBI_MODULATION_NRZ_MSB,   VBI_MODULATION_BIPHASE_LSB,   VBI_MODULATION_BIPHASE_MSB }
	Modulation used for VBI data transmission. More...
Functions
void	vbi_bit_slicer_init (vbi_bit_slicer *slicer, int raw_samples, int sampling_rate, int cri_rate, int bit_rate, unsigned int cri_frc, unsigned int cri_mask, int cri_bits, int frc_bits, int payload, vbi_modulation modulation, vbi_pixfmt fmt)
_vbi_inline vbi_bool	vbi_bit_slice (vbi_bit_slicer *slicer, uint8_t *raw, uint8_t *buf)
void	vbi_raw_decoder_init (vbi_raw_decoder *rd)
void	vbi_raw_decoder_reset (vbi_raw_decoder *rd)
void	vbi_raw_decoder_destroy (vbi_raw_decoder *rd)
unsigned int	vbi_raw_decoder_add_services (vbi_raw_decoder *rd, unsigned int services, int strict)
unsigned int	vbi_raw_decoder_check_services (vbi_raw_decoder *rd, unsigned int services, int strict)
unsigned int	vbi_raw_decoder_remove_services (vbi_raw_decoder *rd, unsigned int services)
void	vbi_raw_decoder_resize (vbi_raw_decoder *rd, int *start, unsigned int *count)
unsigned int	vbi_raw_decoder_parameters (vbi_raw_decoder *rd, unsigned int services, int scanning, int *max_rate)
int	vbi_raw_decode (vbi_raw_decoder *rd, uint8_t *raw, vbi_sliced *out)

---

Detailed Description

Converting raw VBI samples to bits and bytes.

The libzvbi already offers hardware interfaces to obtain sliced VBI data for further processing. However if you want to write your own interface or decode data services not covered by libzvbi you can use these lower level functions.

---

Typedef Documentation

typedef struct vbi_bit_slicer vbi_bit_slicer

Bit slicer context.

The contents of this structure are private, use vbi_bit_slicer_init() to initialize.

typedef struct vbi_raw_decoder vbi_raw_decoder

Raw vbi decoder context.

Only the sampling parameters are public. See vbi_raw_decoder_parameters() and vbi_raw_decoder_add_services() for usage.

---

Enumeration Type Documentation

enum vbi_pixfmt

Image format used as source to vbi_bit_slice() and vbi_raw_decode().

Symbol	Byte 0	Byte 1	Byte 2	Byte 3
Planar YUV 4:2:0 data.
VBI_PIXFMT_YUV420	Y plane U plane V plane Y00 Y01 Y02 Y03 Y10 Y11 Y12 Y13 Y20 Y21 Y22 Y23 Y30 Y31 Y32 Y33 Cb00 Cb01 Cb10 Cb11 Cr00 Cr01 Cr10 Cr11
Packed YUV 4:2:2 data.
VBI_PIXFMT_YUYV	Y0	Cb	Y1	Cr
VBI_PIXFMT_YVYU	Y0	Cr	Y1	Cb
VBI_PIXFMT_UYVY	Cb	Y0	Cr	Y1
VBI_PIXFMT_VYUY	Cr	Y0	Cb	Y1
Packed 32 bit RGB data.
VBI_PIXFMT_RGBA32_LE VBI_PIXFMT_ARGB32_BE	r7 ... r0	g7 ... g0	b7 ... b0	a7 ... a0
VBI_PIXFMT_BGRA32_LE VBI_PIXFMT_ARGB32_BE	b7 ... b0	g7 ... g0	r7 ... r0	a7 ... a0
VBI_PIXFMT_ARGB32_LE VBI_PIXFMT_BGRA32_BE	a7 ... a0	r7 ... r0	g7 ... g0	b7 ... b0
VBI_PIXFMT_ABGR32_LE VBI_PIXFMT_RGBA32_BE	a7 ... a0	b7 ... b0	g7 ... g0	r7 ... r0
Packed 24 bit RGB data.
VBI_PIXFMT_RGBA24	r7 ... r0	g7 ... g0	b7 ... b0
VBI_PIXFMT_BGRA24	b7 ... b0	g7 ... g0	r7 ... r0
Packed 16 bit RGB data.
VBI_PIXFMT_RGB16_LE	g2 g1 g0 r4 r3 r2 r1 r0	b4 b3 b2 b1 b0 g5 g4 g3
VBI_PIXFMT_BGR16_LE	g2 g1 g0 b4 b3 b2 b1 b0	r4 r3 r2 r1 r0 g5 g4 g3
VBI_PIXFMT_RGB16_BE	b4 b3 b2 b1 b0 g5 g4 g3	g2 g1 g0 r4 r3 r2 r1 r0
VBI_PIXFMT_BGR16_BE	r4 r3 r2 r1 r0 g5 g4 g3	g2 g1 g0 b4 b3 b2 b1 b0
Packed 15 bit RGB data.
VBI_PIXFMT_RGBA15_LE	g2 g1 g0 r4 r3 r2 r1 r0	a0 b4 b3 b2 b1 b0 g4 g3
VBI_PIXFMT_BGRA15_LE	g2 g1 g0 b4 b3 b2 b1 b0	a0 r4 r3 r2 r1 r0 g4 g3
VBI_PIXFMT_ARGB15_LE	g1 g0 r4 r3 r2 r1 r0 a0	b4 b3 b2 b1 b0 g4 g3 g2
VBI_PIXFMT_ABGR15_LE	g1 g0 b4 b3 b2 b1 b0 a0	r4 r3 r2 r1 r0 g4 g3 g2
VBI_PIXFMT_RGBA15_BE	a0 b4 b3 b2 b1 b0 g4 g3	g2 g1 g0 r4 r3 r2 r1 r0
VBI_PIXFMT_BGRA15_BE	a0 r4 r3 r2 r1 r0 g4 g3	g2 g1 g0 b4 b3 b2 b1 b0
VBI_PIXFMT_ARGB15_BE	b4 b3 b2 b1 b0 g4 g3 g2	g1 g0 r4 r3 r2 r1 r0 a0
VBI_PIXFMT_ABGR15_BE	r4 r3 r2 r1 r0 g4 g3 g2	g1 g0 b4 b3 b2 b1 b0 a0

enum vbi_modulation

Modulation used for VBI data transmission.

Enumerator:

VBI_MODULATION_NRZ_LSB	The data is 'non-return to zero' coded, logical '1' bits are described by high sample values, logical '0' bits by low values. The data is last significant bit first transmitted.
VBI_MODULATION_NRZ_MSB	'Non-return to zero' coded, most significant bit first transmitted.
VBI_MODULATION_BIPHASE_LSB	The data is 'bi-phase' coded. Each data bit is described by two complementary signalling elements, a logical '1' by a sequence of '10' elements, a logical '0' by a '01' sequence. The data is last significant bit first transmitted.
VBI_MODULATION_BIPHASE_MSB	'Bi-phase' coded, most significant bit first transmitted.

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Function Documentation

void vbi_bit_slicer_init	(	vbi_bit_slicer *	slicer,
		int	raw_samples,
		int	sampling_rate,
		int	cri_rate,
		int	bit_rate,
		unsigned int	cri_frc,
		unsigned int	cri_mask,
		int	cri_bits,
		int	frc_bits,
		int	payload,
		vbi_modulation	modulation,
		vbi_pixfmt	fmt
	)

Parameters:

slicer	Pointer to vbi_bit_slicer object to be initialized.
raw_samples	Number of samples or pixels in one raw vbi line later passed to vbi_bit_slice(). This limits the number of bytes read from the sample buffer.
sampling_rate	Raw vbi sampling rate in Hz, that is the number of samples or pixels sampled per second by the hardware.
cri_rate	The Clock Run In is a NRZ modulated sequence of '0' and '1' bits prepending most data transmissions to synchronize data acquisition circuits. This parameter gives the CRI bit rate in Hz, that is the number of CRI bits transmitted per second.
bit_rate	The transmission bit rate of all data bits following the CRI in Hz.
cri_frc	The FRaming Code usually following the CRI is a bit sequence identifying the data service, and per libzvbi definition modulated and transmitted at the same bit rate as the payload (however nothing stops you from counting all nominal CRI and FRC bits as CRI). The bit slicer compares the bits in this word, lsb last transmitted, against the transmitted CRI and FRC. Decoding of payload starts with the next bit after a match.
cri_mask	Of the CRI bits in cri_frc, only these bits are actually significant for a match. For instance it is wise not to rely on the very first CRI bits transmitted. Note this mask is not shifted left by frc_bits.
cri_bits
frc_bits	Number of CRI and FRC bits in cri_frc, respectively. Their sum is limited to 32.
payload	Number of payload bits. Only this data will be stored in the vbi_bit_slice() output. If this number is no multiple of eight, the most significant bits of the last byte are undefined.
modulation	Modulation of the vbi data, see vbi_modulation.
fmt	Format of the raw data, see vbi_pixfmt.

Initializes vbi_bit_slicer object. Usually you will not use this function but vbi_raw_decode(), the vbi image decoder which handles all these details.

_vbi_inline vbi_bool vbi_bit_slice	(	vbi_bit_slicer *	slicer,
		uint8_t *	raw,
		uint8_t *	buf
	)

Parameters:

slicer	Pointer to initialized vbi_bit_slicer object.
raw	Input data. At least the number of pixels or samples given as raw_samples to vbi_bit_slicer_init().
buf	Output data. The buffer must be large enough to store the number of bits given as payload to vbi_bit_slicer_init().

Decode one scan line of raw vbi data. Note the bit slicer tries to adapt to the average signal amplitude, you should avoid using the same vbi_bit_slicer object for data from different devices.

Note:

As a matter of speed this function does not lock the slicer. When you want to share a vbi_bit_slicer object between multiple threads you must implement your own locking mechanism.

Returns:

FALSE if the raw data does not contain the expected information, i. e. the CRI/FRC has not been found. This may also result from a too weak or noisy signal. Error correction must be implemented at a higher layer.

void vbi_raw_decoder_init

(

vbi_raw_decoder *

rd

)

Parameters:

rd	Pointer to a vbi_raw_decoder structure.

Initializes a vbi_raw_decoder structure.

void vbi_raw_decoder_reset

(

vbi_raw_decoder *

rd

)

Parameters:

rd	Initialized vbi_raw_decoder structure.

Reset a vbi_raw_decoder structure. This removes all previously added services to be decoded (if any) but does not touch the sampling parameters. You are free to change the sampling parameters after calling this.

void vbi_raw_decoder_destroy

(

vbi_raw_decoder *

rd

)

Parameters:

rd	Pointer to initialized vbi_raw_decoder structure, can be NULL.

Free all resources associated with rd.

unsigned int vbi_raw_decoder_add_services	(	vbi_raw_decoder *	rd,
		unsigned int	services,
		int	strict
	)

Parameters:

rd	Initialized vbi_raw_decoder structure.
services	Set of VBI_SLICED_ symbols.
strict	A value of 0, 1 or 2 requests loose, reliable or strict matching of sampling parameters. For example if the data service requires knowledge of line numbers while they are not known, 0 will accept the service (which may work if the scan lines are populated in a non-confusing way) but 1 or 2 will not. If the data service may use more lines than are sampled, 1 will accept but 2 will not. If unsure, set to 1.

After you initialized the sampling parameters in rd (according to the abilities of your raw vbi source), this function adds one or more data services to be decoded. The libzvbi raw vbi decoder can decode up to eight data services in parallel. You can call this function while already decoding, it does not change sampling parameters and you must not change them either after calling this.

Returns:

Set of VBI_SLICED_ symbols describing the data services that actually will be decoded. This excludes those services not decodable given the sampling parameters in rd.

unsigned int vbi_raw_decoder_check_services	(	vbi_raw_decoder *	rd,
		unsigned int	services,
		int	strict
	)

Parameters:

rd	Initialized vbi_raw_decoder structure.
services	Set of VBI_SLICED_ symbols.
strict	See description of vbi_raw_decoder_add_services()

Check which of the given services can be decoded with current capture parameters at a given strictness level.

Returns:

Subset of services actually decodable.

unsigned int vbi_raw_decoder_remove_services	(	vbi_raw_decoder *	rd,
		unsigned int	services
	)

Parameters:

rd	Initialized vbi_raw_decoder structure.
services	Set of VBI_SLICED_ symbols.

Removes one or more data services to be decoded from the vbi_raw_decoder structure. This function can be called at any time and does not touch sampling parameters.

Returns:

Set of VBI_SLICED_ symbols describing the remaining data services that will be decoded.

void vbi_raw_decoder_resize	(	vbi_raw_decoder *	rd,
		int *	start,
		unsigned int *	count
	)

Parameters:

rd	Initialized vbi_raw_decoder structure.
start	Array of start line indices for both fields
count	Array of line counts for both fields

Grows or shrinks the internal state arrays for VBI geometry changes

unsigned int vbi_raw_decoder_parameters	(	vbi_raw_decoder *	rd,
		unsigned int	services,
		int	scanning,
		int *	max_rate
	)

Parameters:

rd	Initialized vbi_raw_decoder structure.
services	Set of VBI_SLICED_ symbols. Here (and only here) you can add VBI_SLICED_VBI_625 or VBI_SLICED_VBI_525 to include all vbi scan lines in the calculated sampling parameters.
scanning	When 525 accept only NTSC services, when 625 only PAL/SECAM services. When scanning is 0, determine the scanning from the requested services, an ambiguous set will pick a 525 or 625 line system at random.
max_rate	If given, the highest data bit rate in Hz of all services requested is stored here. (The sampling rate should be at least twice as high; rd->sampling_rate will be set to a more reasonable value of 27 MHz derived from ITU-R Rec. 601.)

Calculate the sampling parameters in rd required to receive and decode the requested data services. rd->sampling_format will be VBI_PIXFMT_YUV420, rd->bytes_per_line set accordingly to a reasonable minimum. This function can be used to initialize hardware prior to calling vbi_raw_decoder_add_service().

Returns:

Set of VBI_SLICED_ symbols describing the data services covered by the calculated sampling parameters. This excludes services the libzvbi raw decoder cannot decode.

int vbi_raw_decode	(	vbi_raw_decoder *	rd,
		uint8_t *	raw,
		vbi_sliced *	out
	)

Parameters:

rd	Initialized vbi_raw_decoder structure.
raw	A raw vbi image as defined in the vbi_raw_decoder structure (rd->sampling_format, rd->bytes_per_line, rd->count[0] + rd->count[1] scan lines).
out	Buffer to store the decoded vbi_sliced data. Since every vbi scan line may contain data, this must be an array of vbi_sliced with the same number of entries as scan lines in the raw image (rd->count[0] + rd->count[1]).

Decode a raw vbi image, consisting of several scan lines of raw vbi data, into sliced vbi data. The output is sorted by line number.

Note this function attempts to learn which lines carry which data service, or none, to speed up decoding. You should avoid using the same vbi_raw_decoder structure for different sources.

Returns:

The number of lines decoded, i. e. the number of vbi_sliced records written.