codec.h File Reference

The shared libtheoradec and libtheoraenc C API. More...

#include <ogg/ogg.h>

Go to the source code of this file.

Data Structures
struct	th_img_plane
	A buffer for a single color plane in an uncompressed image. More...
struct	th_info
	Theora bitstream information. More...
struct	th_comment
	The comment information. More...
struct	th_quant_ranges
	A set of qi ranges. More...
struct	th_quant_info
	A complete set of quantization parameters. More...
struct	th_huff_code
	A Huffman code for a Theora DCT token. More...
Return codes
#define	TH_EFAULT   (-1)
	An invalid pointer was provided.
#define	TH_EINVAL   (-10)
	An invalid argument was provided.
#define	TH_EBADHEADER   (-20)
	The contents of the header were incomplete, invalid, or unexpected.
#define	TH_ENOTFORMAT   (-21)
	The header does not belong to a Theora stream.
#define	TH_EVERSION   (-22)
	The bitstream version is too high.
#define	TH_EIMPL   (-23)
	The specified function is not implemented.
#define	TH_EBADPACKET   (-24)
	There were errors in the video data packet.
#define	TH_DUPFRAME   (1)
	The decoded packet represented a dropped frame.
Basic shared functions
const char *	th_version_string (void)
	Retrieves a human-readable string to identify the library vendor and version.
ogg_uint32_t	th_version_number (void)
	Retrieves the library version number.
ogg_int64_t	th_granule_frame (void *_encdec, ogg_int64_t _granpos)
	Converts a granule position to an absolute frame index, starting at 0.
double	th_granule_time (void *_encdec, ogg_int64_t _granpos)
	Converts a granule position to an absolute time in seconds.
int	th_packet_isheader (ogg_packet *_op)
	Determines whether a Theora packet is a header or not.
int	th_packet_iskeyframe (ogg_packet *_op)
	Determines whether a theora packet is a key frame or not.
Functions for manipulating header data
void	th_info_init (th_info *_info)
	Initializes a th_info structure.
void	th_info_clear (th_info *_info)
	Clears a th_info structure.
void	th_comment_init (th_comment *_tc)
	Initialize a th_comment structure.
void	th_comment_add (th_comment *_tc, char *_comment)
	Add a comment to an initialized th_comment structure.
void	th_comment_add_tag (th_comment *_tc, char *_tag, char *_val)
	Add a comment to an initialized th_comment structure.
char *	th_comment_query (th_comment *_tc, char *_tag, int _count)
	Look up a comment value by its tag.
int	th_comment_query_count (th_comment *_tc, char *_tag)
	Look up the number of instances of a tag.
void	th_comment_clear (th_comment *_tc)
	Clears a th_comment structure.
Defines
#define	_O_THEORA_CODEC_H_   (1)
#define	TH_NHUFFMAN_TABLES   (80)
	The number of Huffman tables used by Theora.
#define	TH_NDCT_TOKENS   (32)
	The number of DCT token values in each table.
Typedefs
typedef th_img_plane	th_ycbcr_buffer [3]
	A complete image buffer for an uncompressed frame.
typedef th_comment	th_comment
	The comment information.
typedef unsigned char	th_quant_base [64]
	A single base matrix.
Enumerations
enum	th_colorspace { TH_CS_UNSPECIFIED, TH_CS_ITU_REC_470M, TH_CS_ITU_REC_470BG, TH_CS_NSPACES }
	The currently defined color space tags. More...
enum	th_pixel_fmt {   TH_PF_420, TH_PF_RSVD, TH_PF_422, TH_PF_444,   TH_PF_NFORMATS }
	The currently defined pixel format tags. More...

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Detailed Description

The shared libtheoradec and libtheoraenc C API.

You don't need to include this directly.

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Define Documentation

#define _O_THEORA_CODEC_H_   (1)

#define TH_DUPFRAME   (1)

The decoded packet represented a dropped frame. The player can continue to display the current frame, as the contents of the decoded frame buffer have not changed.

#define TH_EBADHEADER   (-20)

The contents of the header were incomplete, invalid, or unexpected.

#define TH_EBADPACKET   (-24)

There were errors in the video data packet.

#define TH_EFAULT   (-1)

An invalid pointer was provided.

#define TH_EIMPL   (-23)

The specified function is not implemented.

#define TH_EINVAL   (-10)

An invalid argument was provided.

#define TH_ENOTFORMAT   (-21)

The header does not belong to a Theora stream.

#define TH_EVERSION   (-22)

The bitstream version is too high.

#define TH_NDCT_TOKENS   (32)

The number of DCT token values in each table.

#define TH_NHUFFMAN_TABLES   (80)

The number of Huffman tables used by Theora.

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Typedef Documentation

typedef struct th_comment th_comment

The comment information. This structure holds the in-stream metadata corresponding to the 'comment' header packet. The comment header is meant to be used much like someone jotting a quick note on the label of a video. It should be a short, to the point text note that can be more than a couple words, but not more than a short paragraph. The metadata is stored as a series of (tag, value) pairs, in length-encoded string vectors. The first occurrence of the '=' character delimits the tag and value. A particular tag may occur more than once, and order is significant. The character set encoding for the strings is always UTF-8, but the tag names are limited to ASCII, and treated as case-insensitive. See the Theora specification, Section 6.3.3 for details. In filling in this structure, th_decode_headerin() will null-terminate the user_comment strings for safety. However, the bitstream format itself treats them as 8-bit clean vectors, possibly containing null characters, and so the length array should be treated as their authoritative length.

typedef unsigned char th_quant_base[64]

A single base matrix.

typedef th_img_plane th_ycbcr_buffer[3]

A complete image buffer for an uncompressed frame. The chroma planes may be decimated by a factor of two in either direction, as indicated by th_info::pixel_fmt. The width and height of the Y' plane must be multiples of 16. They may need to be cropped for display, using the rectangle specified by th_info::pic_x, th_info::pic_y, th_info::pic_width, and th_info::pic_height. All samples are 8 bits. Note: The term YUV often used to describe a colorspace is ambiguous. The exact parameters of the RGB to YUV conversion process aside, in many contexts the U and V channels actually have opposite meanings. To avoid this confusion, we are explicit: the name of the color channels are Y'CbCr, and they appear in that order, always. The prime symbol denotes that the Y channel is non-linear. Cb and Cr stand for "Chroma blue" and "Chroma red", respectively.

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Enumeration Type Documentation

enum th_colorspace

The currently defined color space tags. See the Theora specification, Chapter 4, for exact details on the meaning of each of these color spaces. Enumerator: TH_CS_UNSPECIFIED  The color space was not specified at the encoder. It may be conveyed by an external means. TH_CS_ITU_REC_470M  A color space designed for NTSC content. TH_CS_ITU_REC_470BG  A color space designed for PAL/SECAM content. TH_CS_NSPACES  The total number of currently defined color spaces.

enum th_pixel_fmt

The currently defined pixel format tags. See the Theora specification, Section 4.4, for details on the precise sample locations. Enumerator: TH_PF_420  Chroma decimation by 2 in both the X and Y directions (4:2:0). The Cb and Cr chroma planes are half the width and half the height of the luma plane. TH_PF_RSVD  Currently reserved. TH_PF_422  Chroma decimation by 2 in the X direction (4:2:2). The Cb and Cr chroma planes are half the width of the luma plane, but full height. TH_PF_444  No chroma decimation (4:4:4). The Cb and Cr chroma planes are full width and full height. TH_PF_NFORMATS  The total number of currently defined pixel formats.

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Function Documentation

void th_comment_add (  th_comment *  _tc, char *  _comment )

Add a comment to an initialized th_comment structure. Note: Neither th_comment_add() nor th_comment_add_tag() support comments containing null values, although the bitstream format does support them. To add such comments you will need to manipulate the th_comment structure directly. Parameters: _tc  The th_comment struct to add the comment to. _comment  Must be a null-terminated UTF-8 string containing the comment in "TAG=the value" form.

void th_comment_add_tag (  th_comment *  _tc, char *  _tag, char *  _val )

Add a comment to an initialized th_comment structure. Note: Neither th_comment_add() nor th_comment_add_tag() support comments containing null values, although the bitstream format does support them. To add such comments you will need to manipulate the th_comment structure directly. Parameters: _tc  The th_comment struct to add the comment to. _tag  A null-terminated string containing the tag associated with the comment. _val  The corresponding value as a null-terminated string.

void th_comment_clear (  th_comment *  _tc  )

Clears a th_comment structure. This should be called on a th_comment structure after it is no longer needed. It will free all memory used by the structure members. Parameters: _tc  The th_comment struct to clear.

void th_comment_init (  th_comment *  _tc  )

Initialize a th_comment structure. This should be called on a freshly allocated th_comment structure before attempting to use it. Parameters: _tc  The th_comment struct to initialize.

char* th_comment_query (  th_comment *  _tc, char *  _tag, int  _count )

Look up a comment value by its tag. Parameters: _tc  An initialized th_comment structure. _tag  The tag to look up. _count  The instance of the tag. The same tag can appear multiple times, each with a distinct value, so an index is required to retrieve them all. The order in which these values appear is significant and should be preserved. Use th_comment_query_count() to get the legal range for the _count parameter. Returns: A pointer to the queried tag's value. This points directly to data in the th_comment structure. It should not be modified or freed by the application, and modifications to the structure may invalidate the pointer. Return values: NULL  If no matching tag is found.

int th_comment_query_count (  th_comment *  _tc, char *  _tag )

Look up the number of instances of a tag. Call this first when querying for a specific tag and then iterate over the number of instances with separate calls to th_comment_query() to retrieve all the values for that tag in order. Parameters: _tc  An initialized th_comment structure. _tag  The tag to look up. Returns: The number on instances of this particular tag.

ogg_int64_t th_granule_frame (  void *  _encdec, ogg_int64_t  _granpos )

Converts a granule position to an absolute frame index, starting at 0. The granule position is interpreted in the context of a given th_enc_ctx or th_dec_ctx handle (either will suffice). Parameters: _encdec  A previously allocated th_enc_ctx or th_dec_ctx handle. _granpos  The granule position to convert. Returns: The absolute frame index corresponding to _granpos. Return values: -1  The given granule position was invalid (i.e. negative).

double th_granule_time (  void *  _encdec, ogg_int64_t  _granpos )

Converts a granule position to an absolute time in seconds. The granule position is interpreted in the context of a given th_enc_ctx or th_dec_ctx handle (either will suffice). Parameters: _encdec  A previously allocated th_enc_ctx or th_dec_ctx handle. _granpos  The granule position to convert. Returns: The absolute time in seconds corresponding to _granpos. This is the "end time" for the frame, or the latest time it should be displayed. It is not the presentation time. Return values: -1  The given granule position was invalid (i.e. negative).

void th_info_clear (  th_info *  _info  )

Clears a th_info structure. This should be called on a th_info structure after it is no longer needed. Parameters: _info  The th_info struct to clear.

void th_info_init (  th_info *  _info  )

Initializes a th_info structure. This should be called on a freshly allocated th_info structure before attempting to use it. Parameters: _info  The th_info struct to initialize.

int th_packet_isheader (  ogg_packet *  _op  )

Determines whether a Theora packet is a header or not. This function does no verification beyond checking the packet type bit, so it should not be used for bitstream identification; use th_decode_headerin() for that. As per the Theora specification, an empty (0-byte) packet is treated as a data packet (a delta frame with no coded blocks). Parameters: _op  An ogg_packet containing encoded Theora data. Return values: 1  The packet is a header packet 0  The packet is a video data packet.

int th_packet_iskeyframe (  ogg_packet *  _op  )

Determines whether a theora packet is a key frame or not. This function does no verification beyond checking the packet type and key frame bits, so it should not be used for bitstream identification; use th_decode_headerin() for that. As per the Theora specification, an empty (0-byte) packet is treated as a delta frame (with no coded blocks). Parameters: _op  An ogg_packet containing encoded Theora data. Return values: 1  The packet contains a key frame. 0  The packet contains a delta frame. -1  The packet is not a video data packet.

ogg_uint32_t th_version_number (  void   )

Retrieves the library version number. This is the highest bitstream version that the encoder library will produce, or that the decoder library can decode. This number is composed of a 16-bit major version, 8-bit minor version and 8 bit sub-version, composed as follows: (VERSION_MAJOR<<16)+(VERSION_MINOR<<8)+(VERSION_SUBMINOR) Returns: the version number.

const char* th_version_string (  void   )

Retrieves a human-readable string to identify the library vendor and version. Returns: the version string.

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