GstTypeFind

GstTypeFind — Stream type detection

Synopsis

#include <gst/gst.h>

struct              GstTypeFind;
void                (*GstTypeFindFunction)              (GstTypeFind *find,
                                                         gpointer data);
enum                GstTypeFindProbability;
guint8 *            gst_type_find_peek                  (GstTypeFind *find,
                                                         gint64 offset,
                                                         guint size);
void                gst_type_find_suggest               (GstTypeFind *find,
                                                         guint probability,
                                                         const GstCaps *caps);
void                gst_type_find_suggest_simple        (GstTypeFind *find,
                                                         guint probability,
                                                         const char *media_type,
                                                         const char *fieldname,
                                                         ...);
guint64             gst_type_find_get_length            (GstTypeFind *find);
gboolean            gst_type_find_register              (GstPlugin *plugin,
                                                         const gchar *name,
                                                         guint rank,
                                                         GstTypeFindFunction func,
                                                         gchar **extensions,
                                                         const GstCaps *possible_caps,
                                                         gpointer data,
                                                         GDestroyNotify data_notify);

Description

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

Last reviewed on 2005-11-09 (0.9.4)

Details

struct GstTypeFind

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

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

  gpointer     data;

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

Object that stores typefind callbacks. To use with GstTypeFindFactory.

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.

GstTypeFindFunction ()

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

A function that will be called by typefinding.

find :

A GstTypeFind structure

data :

optionnal data to pass to the function

enum GstTypeFindProbability

typedef enum {
  GST_TYPE_FIND_NONE = 0,
  GST_TYPE_FIND_MINIMUM = 1,
  GST_TYPE_FIND_POSSIBLE = 50,
  GST_TYPE_FIND_LIKELY = 80,
  GST_TYPE_FIND_NEARLY_CERTAIN = 99,
  GST_TYPE_FIND_MAXIMUM = 100
} GstTypeFindProbability;

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

GST_TYPE_FIND_NONE

type undetected. Since 0.10.36.

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.

gst_type_find_peek ()

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

returns and must not be freed.

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,
                                                         const 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.

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).

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

... :

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)

Since 0.10.20


gst_type_find_get_length ()

guint64             gst_type_find_get_length            (GstTypeFind *find);

Get the length of the data stream.

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,
                                                         gchar **extensions,
                                                         const 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.

plugin :

A GstPlugin, or NULL for a static typefind function (note that passing NULL only works in GStreamer 0.10.16 and later)

name :

The name for registering

rank :

The rank (or importance) of this typefind function

func :

The GstTypeFindFunction to use

extensions :

Optional extensions that could belong to this type. [transfer none][array zero-terminated=1][element-type utf8]

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