Functions Shared by Encode and Decode

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.

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.