GstTypeFind

GstTypeFind — Stream type detection

Functions

Types and Values

Object Hierarchy


Includes

#include <gst/gst.h>

Description

The following functions allow you to detect the media type of an unknown stream.

Last reviewed on 2005-11-09 (0.9.4)

Functions

GstTypeFindFunction ()

void
(*GstTypeFindFunction) (GstTypeFind *find,
                        gpointer user_data);

A function that will be called by typefinding.

Parameters

find

A GstTypeFind structure

 

user_data

optionnal data to pass to the function

 

gst_type_find_peek ()

const guint8 *
gst_type_find_peek (GstTypeFind *find,
                    gint64 offset,
                    guint size);

returns and must not be freed.

Parameters

find

The GstTypeFind object the function was called with

 

offset

The offset

 

size

The number of bytes to return

 

Returns

the requested data, or NULL if that data is not available.

[transfer none][array length=size]


gst_type_find_suggest ()

void
gst_type_find_suggest (GstTypeFind *find,
                       guint probability,
                       GstCaps *caps);

If a GstTypeFindFunction calls this function it suggests the caps with the given probability. A GstTypeFindFunction may supply different suggestions in one call. It is up to the caller of the GstTypeFindFunction to interpret these values.

Parameters

find

The GstTypeFind object the function was called with

 

probability

The probability in percent that the suggestion is right

 

caps

The fixed GstCaps to suggest

 

gst_type_find_suggest_simple ()

void
gst_type_find_suggest_simple (GstTypeFind *find,
                              guint probability,
                              const char *media_type,
                              const char *fieldname,
                              ...);

If a GstTypeFindFunction calls this function it suggests the caps with the given probability. A GstTypeFindFunction may supply different suggestions in one call. It is up to the caller of the GstTypeFindFunction to interpret these values.

This function is similar to gst_type_find_suggest(), only that instead of passing a GstCaps argument you can create the caps on the fly in the same way as you can with gst_caps_new_simple().

Make sure you terminate the list of arguments with a NULL argument and that the values passed have the correct type (in terms of width in bytes when passed to the vararg function - this applies particularly to gdouble and guint64 arguments).

Parameters

find

The GstTypeFind object the function was called with

 

probability

The probability in percent that the suggestion is right

 

media_type

the media type of the suggested caps

 

fieldname

first field of the suggested caps, or NULL.

[allow-none]

...

additional arguments to the suggested caps in the same format as the arguments passed to gst_structure_new() (ie. triplets of field name, field GType and field value)

 

gst_type_find_get_length ()

guint64
gst_type_find_get_length (GstTypeFind *find);

Get the length of the data stream.

Parameters

find

The GstTypeFind the function was called with

 

Returns

The length of the data stream, or 0 if it is not available.


gst_type_find_register ()

gboolean
gst_type_find_register (GstPlugin *plugin,
                        const gchar *name,
                        guint rank,
                        GstTypeFindFunction func,
                        const gchar *extensions,
                        GstCaps *possible_caps,
                        gpointer data,
                        GDestroyNotify data_notify);

Registers a new typefind function to be used for typefinding. After registering this function will be available for typefinding. This function is typically called during an element's plugin initialization.

Parameters

plugin

A GstPlugin, or NULL for a static typefind function.

[allow-none]

name

The name for registering

 

rank

The rank (or importance) of this typefind function

 

func

The GstTypeFindFunction to use

 

extensions

Optional comma-separated list of extensions that could belong to this type.

[allow-none]

possible_caps

Optionally the caps that could be returned when typefinding succeeds

 

data

Optional user data. This user data must be available until the plugin is unloaded.

 

data_notify

a GDestroyNotify that will be called on data when the plugin is unloaded.

 

Returns

TRUE on success, FALSE otherwise

Types and Values

struct GstTypeFind

struct GstTypeFind {
  /* private to the caller of the typefind function */
  const guint8 *  (* peek)       (gpointer         data,
                                  gint64           offset,
                                  guint            size);

  void            (* suggest)    (gpointer         data,
                                  guint            probability,
                                  GstCaps         *caps);

  gpointer         data;

  /* optional */
  guint64         (* get_length) (gpointer data);
};

Object that stores typefind callbacks. To use with GstTypeFindFactory.

Members

peek ()

Method to peek data.

 

suggest ()

Method to suggest GstCaps with a given probability.

 

gpointer data;

The data used by the caller of the typefinding function.

 

get_length ()

Returns the length of current data.

 

enum GstTypeFindProbability

The probability of the typefind function. Higher values have more certainty in doing a reliable typefind.

Members

GST_TYPE_FIND_NONE

type undetected.

 

GST_TYPE_FIND_MINIMUM

unlikely typefind.

 

GST_TYPE_FIND_POSSIBLE

possible type detected.

 

GST_TYPE_FIND_LIKELY

likely a type was detected.

 

GST_TYPE_FIND_NEARLY_CERTAIN

nearly certain that a type was detected.

 

GST_TYPE_FIND_MAXIMUM

very certain a type was detected.