Teletext PFC packet demultiplexer
[Low Level Decoding]

Functions to decode data transmissions in Teletext Page Function Clear packets (EN 300 708 section 4). More...

Data Structures
struct	vbi_pfc_block
	One block of data returned by vbi_pfc_demux_cb(). More...
Typedefs
typedef struct _vbi_pfc_demux	vbi_pfc_demux
	PFC demultiplexer context.
typedef vbi_bool	vbi_pfc_demux_cb (vbi_pfc_demux *dx, void *user_data, const vbi_pfc_block *block)
Functions
void	vbi_pfc_demux_reset (vbi_pfc_demux *dx) _vbi_nonnull((1))
vbi_bool	vbi_pfc_demux_feed (vbi_pfc_demux *dx, const uint8_t buffer[42])
vbi_bool	vbi_pfc_demux_feed_frame (vbi_pfc_demux *dx, const vbi_sliced *sliced, unsigned int n_lines)
void	vbi_pfc_demux_delete (vbi_pfc_demux *dx)
vbi_pfc_demux *	vbi_pfc_demux_new (vbi_pgno pgno, unsigned int stream, vbi_pfc_demux_cb *callback, void *user_data)

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Detailed Description

Functions to decode data transmissions in Teletext Page Function Clear packets (EN 300 708 section 4).

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Typedef Documentation

typedef struct _vbi_pfc_demux vbi_pfc_demux

PFC demultiplexer context.

The contents of this structure are private.

Call vbi_pfc_demux_new() to allocate a PFC demultiplexer context.

typedef vbi_bool vbi_pfc_demux_cb(vbi_pfc_demux *dx, void *user_data, const vbi_pfc_block *block)

Parameters:

	dx	PFC demultiplexer context returned by vbi_pfx_demux_new() and given to vbi_pfc_demux_feed().
	user_data	User pointer given to vbi_pfc_demux_new().
	block	Structure describing the received data block.

Function called by vbi_pfc_demux_feed() when a new data block is available.

Returns:

FALSE on error, will be returned by vbi_pfc_demux_feed().

Bug:

vbi_pfc_demux_feed() returns the user_data pointer as second parameter the block pointer as third parameter, but prior to version 0.2.26 this function incorrectly defined block as second and user_data as third parameter.

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Function Documentation

void vbi_pfc_demux_reset

(

vbi_pfc_demux *

dx

)

Parameters:

dx

PFC demultiplexer context allocated with vbi_pfc_demux_new().

Resets the PFC demux context, useful for example after a channel change.

vbi_bool vbi_pfc_demux_feed	(	vbi_pfc_demux *	dx,
		const uint8_t	buffer[42]
	)

Parameters:

	dx	PFC demultiplexer context allocated with vbi_pfc_demux_new().
	buffer	Teletext packet (last 42 bytes, i. e. without clock run-in and framing code), as in struct vbi_sliced.

This function takes a raw stream of Teletext packets, filters out the page and stream requested with vbi_pfc_demux_new() and assembles the data transmitted in this page in a buffer. When a data block is complete it calls the output function given to vbi_pfc_demux_new().

Returns:

FALSE if the packet contained incorrectable errors.

vbi_bool vbi_pfc_demux_feed_frame	(	vbi_pfc_demux *	dx,
		const vbi_sliced *	sliced,
		unsigned int	n_lines
	)

Parameters:

	dx	PFC demultiplexer context allocated with vbi_pfc_demux_new().
	sliced	Sliced VBI data.
	n_lines	Number of lines in the sliced array.

This function works like vbi_pfc_demux_feed() but operates on sliced VBI data and filters out VBI_SLICED_TELETEXT_B_625.

Returns:

FALSE if any Teletext lines contained incorrectable errors.

Since:

0.2.26

void vbi_pfc_demux_delete

(

vbi_pfc_demux *

dx

)

Parameters:

dx

PFC demultiplexer context allocated with vbi_pfc_demux_new(), can be NULL.

Frees all resources associated with dx.

vbi_pfc_demux* vbi_pfc_demux_new	(	vbi_pgno	pgno,
		unsigned int	stream,
		vbi_pfc_demux_cb *	callback,
		void *	user_data
	)

Parameters:

	pgno	Page to take PFC data from.
	stream	PFC stream to be demultiplexed.
	callback	Function to be called by vbi_pfc_demux_feed() when a new data block is available.
	user_data	User pointer passed through to cb function.

Allocates a new Page Function Clear (ETS 300 708 section 4) demultiplexer.

Returns:

Pointer to newly allocated PFC demux context which must be freed with vbi_pfc_demux_delete() when done. NULL on failure (out of memory).