GstTypeFindHelper

GstTypeFindHelper — Utility functions for typefinding

Functions

Object Hierarchy


Includes

#include <gst/base/gsttypefindhelper.h>

Description

Utility functions for elements doing typefinding: gst_type_find_helper() does typefinding in pull mode, while gst_type_find_helper_for_buffer() is useful for elements needing to do typefinding in push mode from a chain function.

Functions

gst_type_find_helper ()

GstCaps *
gst_type_find_helper (GstPad *src,
                      guint64 size);

Tries to find what type of data is flowing from the given source GstPad.

Free-function: gst_caps_unref

Parameters

src

A source GstPad

 

size

The length in bytes

 

Returns

the GstCaps corresponding to the data stream. Returns NULL if no GstCaps matches the data stream.

[transfer full][nullable]


gst_type_find_helper_for_buffer ()

GstCaps *
gst_type_find_helper_for_buffer (GstObject *obj,
                                 GstBuffer *buf,
                                 GstTypeFindProbability *prob);

Tries to find what type of data is contained in the given GstBuffer, the assumption being that the buffer represents the beginning of the stream or file.

All available typefinders will be called on the data in order of rank. If a typefinding function returns a probability of GST_TYPE_FIND_MAXIMUM, typefinding is stopped immediately and the found caps will be returned right away. Otherwise, all available typefind functions will the tried, and the caps with the highest probability will be returned, or NULL if the content of the buffer could not be identified.

Free-function: gst_caps_unref

Parameters

obj

object doing the typefinding, or NULL (used for logging).

[allow-none]

buf

a GstBuffer with data to typefind.

[in][transfer none]

prob

location to store the probability of the found caps, or NULL.

[out][allow-none]

Returns

the GstCaps corresponding to the data, or NULL if no type could be found. The caller should free the caps returned with gst_caps_unref().

[transfer full][nullable]


gst_type_find_helper_for_extension ()

GstCaps *
gst_type_find_helper_for_extension (GstObject *obj,
                                    const gchar *extension);

Tries to find the best GstCaps associated with extension .

All available typefinders will be checked against the extension in order of rank. The caps of the first typefinder that can handle extension will be returned.

Free-function: gst_caps_unref

Parameters

obj

object doing the typefinding, or NULL (used for logging).

[allow-none]

extension

an extension

 

Returns

the GstCaps corresponding to extension , or NULL if no type could be found. The caller should free the caps returned with gst_caps_unref().

[transfer full][nullable]


gst_type_find_helper_for_data ()

GstCaps *
gst_type_find_helper_for_data (GstObject *obj,
                               const guint8 *data,
                               gsize size,
                               GstTypeFindProbability *prob);

Tries to find what type of data is contained in the given data , the assumption being that the data represents the beginning of the stream or file.

All available typefinders will be called on the data in order of rank. If a typefinding function returns a probability of GST_TYPE_FIND_MAXIMUM, typefinding is stopped immediately and the found caps will be returned right away. Otherwise, all available typefind functions will the tried, and the caps with the highest probability will be returned, or NULL if the content of data could not be identified.

Free-function: gst_caps_unref

Parameters

obj

object doing the typefinding, or NULL (used for logging).

[allow-none]

data

a pointer with data to typefind.

[in][transfer none]

size

the size of data .

[in][transfer none]

prob

location to store the probability of the found caps, or NULL.

[out][allow-none]

Returns

the GstCaps corresponding to the data, or NULL if no type could be found. The caller should free the caps returned with gst_caps_unref().

[transfer full][nullable]


GstTypeFindHelperGetRangeFunction ()

GstFlowReturn
(*GstTypeFindHelperGetRangeFunction) (GstObject *obj,
                                      GstObject *parent,
                                      guint64 offset,
                                      guint length,
                                      GstBuffer **buffer);

This function will be called by gst_type_find_helper_get_range() when typefinding functions request to peek at the data of a stream at certain offsets. If this function returns GST_FLOW_OK, the result buffer will be stored in buffer . The contents of buffer is invalid for any other return value.

This function is supposed to behave exactly like a GstPadGetRangeFunction.

Parameters

obj

a GstObject that will handle the getrange request

 

parent

the parent of obj or NULL.

[allow-none]

offset

the offset of the range

 

length

the length of the range

 

buffer

a memory location to hold the result buffer

 

Returns

GST_FLOW_OK for success


gst_type_find_helper_get_range ()

GstCaps *
gst_type_find_helper_get_range (GstObject *obj,
                                GstObject *parent,
                                GstTypeFindHelperGetRangeFunction func,
                                guint64 size,
                                const gchar *extension,
                                GstTypeFindProbability *prob);

Utility function to do pull-based typefinding. Unlike gst_type_find_helper() however, this function will use the specified function func to obtain the data needed by the typefind functions, rather than operating on a given source pad. This is useful mostly for elements like tag demuxers which strip off data at the beginning and/or end of a file and want to typefind the stripped data stream before adding their own source pad (the specified callback can then call the upstream peer pad with offsets adjusted for the tag size, for example).

When extension is not NULL, this function will first try the typefind functions for the given extension, which might speed up the typefinding in many cases.

Free-function: gst_caps_unref

Parameters

obj

A GstObject that will be passed as first argument to func

 

parent

the parent of obj or NULL.

[allow-none]

func

A generic GstTypeFindHelperGetRangeFunction that will be used to access data at random offsets when doing the typefinding.

[scope call]

size

The length in bytes

 

extension

extension of the media

 

prob

location to store the probability of the found caps, or NULL.

[out][allow-none]

Returns

the GstCaps corresponding to the data stream. Returns NULL if no GstCaps matches the data stream.

[transfer full][nullable]

Types and Values