GstQuery

GstQuery — Dynamically register new query types. Provide functions to create queries, and to set and parse values in them.

Functions

#define GST_QUERY_TYPE_NAME()
const gchar * gst_query_type_get_name ()
GQuark gst_query_type_to_quark ()
GstQueryType gst_query_type_register ()
GstQueryType gst_query_type_get_by_nick ()
gboolean gst_query_types_contains ()
const GstQueryTypeDefinition * gst_query_type_get_details ()
GstIterator * gst_query_type_iterate_definitions ()
GstQuery * gst_query_ref ()
void gst_query_unref ()
GstQuery * gst_query_copy ()
#define gst_query_make_writable()
GstQuery * gst_query_new_application ()
GstStructure * gst_query_get_structure ()
GstQuery * gst_query_new_convert ()
void gst_query_set_convert ()
void gst_query_parse_convert ()
GstQuery * gst_query_new_position ()
void gst_query_set_position ()
void gst_query_parse_position ()
GstQuery * gst_query_new_duration ()
void gst_query_set_duration ()
void gst_query_parse_duration ()
GstQuery * gst_query_new_latency ()
void gst_query_parse_latency ()
void gst_query_set_latency ()
GstQuery * gst_query_new_seeking ()
void gst_query_set_seeking ()
void gst_query_parse_seeking ()
GstQuery * gst_query_new_formats ()
void gst_query_set_formats ()
void gst_query_set_formatsv ()
void gst_query_parse_formats_length ()
void gst_query_parse_formats_nth ()
GstQuery * gst_query_new_segment ()
void gst_query_set_segment ()
void gst_query_parse_segment ()
GstQuery * gst_query_new_buffering ()
void gst_query_set_buffering_percent ()
void gst_query_parse_buffering_percent ()
void gst_query_set_buffering_stats ()
void gst_query_parse_buffering_stats ()
void gst_query_set_buffering_range ()
void gst_query_parse_buffering_range ()
gboolean gst_query_add_buffering_range ()
guint gst_query_get_n_buffering_ranges ()
gboolean gst_query_parse_nth_buffering_range ()
GstQuery * gst_query_new_uri ()
void gst_query_parse_uri ()
void gst_query_set_uri ()

Types and Values

Includes

#include <gst/gst.h>

Description

GstQuery functions are used to register new query types to the gstreamer core and use them. Queries can be performed on pads (gst_pad_query()) and elements (gst_element_query()). Please note that some queries might need a running pipeline to work.

Queries can be created using the gst_query_new_*() functions. Query values can be set using gst_query_set_*(), and parsed using gst_query_parse_*() helpers.

The following example shows how to query the duration of a pipeline:

Example 16. Query duration on a pipeline

 GstQuery *query;
 gboolean res;
 query = gst_query_new_duration (GST_FORMAT_TIME);
 res = gst_element_query (pipeline, query);
 if (res) {
   gint64 duration;
   gst_query_parse_duration (query, NULL, &duration);
   g_print ("duration = %"GST_TIME_FORMAT, GST_TIME_ARGS (duration));
 }
 else {
   g_print ("duration query failed...");
 }
 gst_query_unref (query);
 

Last reviewed on 2006-02-14 (0.10.4)

Functions

GST_QUERY_TYPE_NAME()

#define GST_QUERY_TYPE_NAME(query) (gst_query_type_get_name(GST_QUERY_TYPE(query)))

Get a constant string representation of the GstQueryType of the query.

Parameters

query

the query to query

 

Since: 0.10.4


gst_query_type_get_name ()

const gchar *
gst_query_type_get_name (GstQueryType query);

Get a printable name for the given query type. Do not modify or free.

Parameters

query

the query type

 

Returns

a reference to the static name of the query.


gst_query_type_to_quark ()

GQuark
gst_query_type_to_quark (GstQueryType query);

Get the unique quark for the given query type.

Parameters

query

the query type

 

Returns

the quark associated with the query type


gst_query_type_register ()

GstQueryType
gst_query_type_register (const gchar *nick,
                         const gchar *description);

Create a new GstQueryType based on the nick or return an already registered query with that nick

Parameters

nick

The nick of the new query

 

description

The description of the new query

 

Returns

A new GstQueryType or an already registered query with the same nick.


gst_query_type_get_by_nick ()

GstQueryType
gst_query_type_get_by_nick (const gchar *nick);

Get the query type registered with nick .

Parameters

nick

The nick of the query

 

Returns

The query registered with nick or GST_QUERY_NONE if the query was not registered.


gst_query_types_contains ()

gboolean
gst_query_types_contains (const GstQueryType *types,
                          GstQueryType type);

See if the given GstQueryType is inside the types query types array.

Parameters

types

The query array to search

 

type

the GstQueryType to find

 

Returns

TRUE if the type is found inside the array


gst_query_type_get_details ()

const GstQueryTypeDefinition *
gst_query_type_get_details (GstQueryType type);

Get details about the given GstQueryType.

Parameters

type

a GstQueryType

 

Returns

The GstQueryTypeDefinition for type or NULL on failure.


gst_query_type_iterate_definitions ()

GstIterator *
gst_query_type_iterate_definitions (void);

Get a GstIterator of all the registered query types. The definitions iterated over are read only.

Free-function: gst_iterator_free

Returns

a GstIterator of GstQueryTypeDefinition.

[transfer full]


gst_query_ref ()

GstQuery *
gst_query_ref (GstQuery *q);

Increases the refcount of the given query by one.

Parameters

q

a GstQuery to increase the refcount of.

 

Returns

q


gst_query_unref ()

void
gst_query_unref (GstQuery *q);

Decreases the refcount of the query. If the refcount reaches 0, the query will be freed.

Parameters

q

a GstQuery to decrease the refcount of.

 

gst_query_copy ()

GstQuery *
gst_query_copy (const GstQuery *q);

Copies the given query using the copy function of the parent GstStructure.

Free-function: gst_query_unref

Parameters

q

a GstQuery to copy.

 

Returns

a new copy of q .

[transfer full]


gst_query_make_writable()

#define         gst_query_make_writable(q)      GST_QUERY_CAST (gst_mini_object_make_writable (GST_MINI_OBJECT_CAST (q)))

Makes a writable query from the given query.

Parameters

q

a GstQuery to make writable.

[transfer full]

Returns

a new writable query (possibly same as q ).

[transfer full]


gst_query_new_application ()

GstQuery *
gst_query_new_application (GstQueryType type,
                           GstStructure *structure);

Constructs a new custom application query object. Use gst_query_unref() when done with it.

Free-function: gst_query_unref

Parameters

type

the query type

 

structure

a structure for the query

 

Returns

a new GstQuery.

[transfer full]


gst_query_get_structure ()

GstStructure *
gst_query_get_structure (GstQuery *query);

Get the structure of a query.

Parameters

query

a GstQuery

 

Returns

the GstStructure of the query. The structure is still owned by the query and will therefore be freed when the query is unreffed.

[transfer none]


gst_query_new_convert ()

GstQuery *
gst_query_new_convert (GstFormat src_format,
                       gint64 value,
                       GstFormat dest_format);

Constructs a new convert query object. Use gst_query_unref() when done with it. A convert query is used to ask for a conversion between one format and another.

Free-function: gst_query_unref

Parameters

src_format

the source GstFormat for the new query

 

value

the value to convert

 

dest_format

the target GstFormat

 

Returns

a GstQuery.

[transfer full]


gst_query_set_convert ()

void
gst_query_set_convert (GstQuery *query,
                       GstFormat src_format,
                       gint64 src_value,
                       GstFormat dest_format,
                       gint64 dest_value);

Answer a convert query by setting the requested values.

Parameters

query

a GstQuery

 

src_format

the source GstFormat

 

src_value

the source value

 

dest_format

the destination GstFormat

 

dest_value

the destination value

 

gst_query_parse_convert ()

void
gst_query_parse_convert (GstQuery *query,
                         GstFormat *src_format,
                         gint64 *src_value,
                         GstFormat *dest_format,
                         gint64 *dest_value);

Parse a convert query answer. Any of src_format , src_value , dest_format , and dest_value may be NULL, in which case that value is omitted.

Parameters

query

a GstQuery

 

src_format

the storage for the GstFormat of the source value, or NULL.

[out][allow-none]

src_value

the storage for the source value, or NULL.

[out][allow-none]

dest_format

the storage for the GstFormat of the destination value, or NULL.

[out][allow-none]

dest_value

the storage for the destination value, or NULL.

[out][allow-none]

gst_query_new_position ()

GstQuery *
gst_query_new_position (GstFormat format);

Constructs a new query stream position query object. Use gst_query_unref() when done with it. A position query is used to query the current position of playback in the streams, in some format.

Free-function: gst_query_unref

Parameters

format

the default GstFormat for the new query

 

Returns

a new GstQuery.

[transfer full]


gst_query_set_position ()

void
gst_query_set_position (GstQuery *query,
                        GstFormat format,
                        gint64 cur);

Answer a position query by setting the requested value in the given format.

Parameters

query

a GstQuery with query type GST_QUERY_POSITION

 

format

the requested GstFormat

 

cur

the position to set

 

gst_query_parse_position ()

void
gst_query_parse_position (GstQuery *query,
                          GstFormat *format,
                          gint64 *cur);

Parse a position query, writing the format into format , and the position into cur , if the respective parameters are non-NULL.

Parameters

query

a GstQuery

 

format

the storage for the GstFormat of the position values (may be NULL).

[out][allow-none]

cur

the storage for the current position (may be NULL).

[out][allow-none]

gst_query_new_duration ()

GstQuery *
gst_query_new_duration (GstFormat format);

Constructs a new stream duration query object to query in the given format. Use gst_query_unref() when done with it. A duration query will give the total length of the stream.

Free-function: gst_query_unref

Parameters

format

the GstFormat for this duration query

 

Returns

a new GstQuery.

[transfer full]


gst_query_set_duration ()

void
gst_query_set_duration (GstQuery *query,
                        GstFormat format,
                        gint64 duration);

Answer a duration query by setting the requested value in the given format.

Parameters

query

a GstQuery

 

format

the GstFormat for the duration

 

duration

the duration of the stream

 

gst_query_parse_duration ()

void
gst_query_parse_duration (GstQuery *query,
                          GstFormat *format,
                          gint64 *duration);

Parse a duration query answer. Write the format of the duration into format , and the value into duration , if the respective variables are non-NULL.

Parameters

query

a GstQuery

 

format

the storage for the GstFormat of the duration value, or NULL.

[out][allow-none]

duration

the storage for the total duration, or NULL.

[out][allow-none]

gst_query_new_latency ()

GstQuery *
gst_query_new_latency (void);

Constructs a new latency query object. Use gst_query_unref() when done with it. A latency query is usually performed by sinks to compensate for additional latency introduced by elements in the pipeline.

Free-function: gst_query_unref

Returns

a GstQuery.

[transfer full]

Since: 0.10.12


gst_query_parse_latency ()

void
gst_query_parse_latency (GstQuery *query,
                         gboolean *live,
                         GstClockTime *min_latency,
                         GstClockTime *max_latency);

Parse a latency query answer.

Parameters

query

a GstQuery

 

live

storage for live or NULL.

[out][allow-none]

min_latency

the storage for the min latency or NULL.

[out][allow-none]

max_latency

the storage for the max latency or NULL.

[out][allow-none]

Since: 0.10.12


gst_query_set_latency ()

void
gst_query_set_latency (GstQuery *query,
                       gboolean live,
                       GstClockTime min_latency,
                       GstClockTime max_latency);

Answer a latency query by setting the requested values in the given format.

Parameters

query

a GstQuery

 

live

if there is a live element upstream

 

min_latency

the minimal latency of the live element

 

max_latency

the maximal latency of the live element

 

Since: 0.10.12


gst_query_new_seeking ()

GstQuery *
gst_query_new_seeking (GstFormat format);

Constructs a new query object for querying seeking properties of the stream.

Free-function: gst_query_unref

Parameters

format

the default GstFormat for the new query

 

Returns

a new GstQuery.

[transfer full]


gst_query_set_seeking ()

void
gst_query_set_seeking (GstQuery *query,
                       GstFormat format,
                       gboolean seekable,
                       gint64 segment_start,
                       gint64 segment_end);

Set the seeking query result fields in query .

Parameters

query

a GstQuery

 

format

the format to set for the segment_start and segment_end values

 

seekable

the seekable flag to set

 

segment_start

the segment_start to set

 

segment_end

the segment_end to set

 

gst_query_parse_seeking ()

void
gst_query_parse_seeking (GstQuery *query,
                         GstFormat *format,
                         gboolean *seekable,
                         gint64 *segment_start,
                         gint64 *segment_end);

Parse a seeking query, writing the format into format , and other results into the passed parameters, if the respective parameters are non-NULL

Parameters

query

a GST_QUERY_SEEKING type query GstQuery

 

format

the format to set for the segment_start and segment_end values, or NULL.

[out][allow-none]

seekable

the seekable flag to set, or NULL.

[out][allow-none]

segment_start

the segment_start to set, or NULL.

[out][allow-none]

segment_end

the segment_end to set, or NULL.

[out][allow-none]

gst_query_new_formats ()

GstQuery *
gst_query_new_formats (void);

Constructs a new query object for querying formats of the stream.

Free-function: gst_query_unref

Returns

a new GstQuery.

[transfer full]

Since: 0.10.4


gst_query_set_formats ()

void
gst_query_set_formats (GstQuery *query,
                       gint n_formats,
                       ...);

Set the formats query result fields in query . The number of formats passed must be equal to n_formats .

Parameters

query

a GstQuery

 

n_formats

the number of formats to set.

 

...

A number of GstFormats equal to n_formats .

 

gst_query_set_formatsv ()

void
gst_query_set_formatsv (GstQuery *query,
                        gint n_formats,
                        const GstFormat *formats);

Set the formats query result fields in query . The number of formats passed in the formats array must be equal to n_formats .

Parameters

query

a GstQuery

 

n_formats

the number of formats to set.

 

formats

an array containing n_formats GstFormat values.

[in][array length=n_formats]

Since: 0.10.4


gst_query_parse_formats_length ()

void
gst_query_parse_formats_length (GstQuery *query,
                                guint *n_formats);

Parse the number of formats in the formats query .

Parameters

query

a GstQuery

 

n_formats

the number of formats in this query.

[out]

Since: 0.10.4


gst_query_parse_formats_nth ()

void
gst_query_parse_formats_nth (GstQuery *query,
                             guint nth,
                             GstFormat *format);

Parse the format query and retrieve the nth format from it into format . If the list contains less elements than nth , format will be set to GST_FORMAT_UNDEFINED.

Parameters

query

a GstQuery

 

nth

the nth format to retrieve.

[out]

format

a pointer to store the nth format.

[out]

Since: 0.10.4


gst_query_new_segment ()

GstQuery *
gst_query_new_segment (GstFormat format);

Constructs a new segment query object. Use gst_query_unref() when done with it. A segment query is used to discover information about the currently configured segment for playback.

Free-function: gst_query_unref

Parameters

format

the GstFormat for the new query

 

Returns

a new GstQuery.

[transfer full]


gst_query_set_segment ()

void
gst_query_set_segment (GstQuery *query,
                       gdouble rate,
                       GstFormat format,
                       gint64 start_value,
                       gint64 stop_value);

Answer a segment query by setting the requested values. The normal playback segment of a pipeline is 0 to duration at the default rate of 1.0. If a seek was performed on the pipeline to play a different segment, this query will return the range specified in the last seek.

start_value and stop_value will respectively contain the configured playback range start and stop values expressed in format . The values are always between 0 and the duration of the media and start_value <= stop_value . rate will contain the playback rate. For negative rates, playback will actually happen from stop_value to start_value .

Parameters

query

a GstQuery

 

rate

the rate of the segment

 

format

the GstFormat of the segment values (start_value and stop_value )

 

start_value

the start value

 

stop_value

the stop value

 

gst_query_parse_segment ()

void
gst_query_parse_segment (GstQuery *query,
                         gdouble *rate,
                         GstFormat *format,
                         gint64 *start_value,
                         gint64 *stop_value);

Parse a segment query answer. Any of rate , format , start_value , and stop_value may be NULL, which will cause this value to be omitted.

See gst_query_set_segment() for an explanation of the function arguments.

Parameters

query

a GstQuery

 

rate

the storage for the rate of the segment, or NULL.

[out][allow-none]

format

the storage for the GstFormat of the values, or NULL.

[out][allow-none]

start_value

the storage for the start value, or NULL.

[out][allow-none]

stop_value

the storage for the stop value, or NULL.

[out][allow-none]

gst_query_new_buffering ()

GstQuery *
gst_query_new_buffering (GstFormat format);

Constructs a new query object for querying the buffering status of a stream.

Free-function: gst_query_new

Parameters

format

the default GstFormat for the new query

 

Returns

a new GstQuery.

[transfer full]

Since: 0.10.20


gst_query_set_buffering_percent ()

void
gst_query_set_buffering_percent (GstQuery *query,
                                 gboolean busy,
                                 gint percent);

Set the percentage of buffered data. This is a value between 0 and 100. The busy indicator is TRUE when the buffering is in progress.

Parameters

query

A valid GstQuery of type GST_QUERY_BUFFERING.

 

busy

if buffering is busy

 

percent

a buffering percent

 

Since: 0.10.20


gst_query_parse_buffering_percent ()

void
gst_query_parse_buffering_percent (GstQuery *query,
                                   gboolean *busy,
                                   gint *percent);

Get the percentage of buffered data. This is a value between 0 and 100. The busy indicator is TRUE when the buffering is in progress.

Parameters

query

A valid GstQuery of type GST_QUERY_BUFFERING.

 

busy

if buffering is busy, or NULL.

[out][allow-none]

percent

a buffering percent, or NULL.

[out][allow-none]

Since: 0.10.20


gst_query_set_buffering_stats ()

void
gst_query_set_buffering_stats (GstQuery *query,
                               GstBufferingMode mode,
                               gint avg_in,
                               gint avg_out,
                               gint64 buffering_left);

Configures the buffering stats values in query .

Parameters

query

A valid GstQuery of type GST_QUERY_BUFFERING.

 

mode

a buffering mode

 

avg_in

the average input rate

 

avg_out

the average output rate

 

buffering_left

amount of buffering time left

 

Since: 0.10.20


gst_query_parse_buffering_stats ()

void
gst_query_parse_buffering_stats (GstQuery *query,
                                 GstBufferingMode *mode,
                                 gint *avg_in,
                                 gint *avg_out,
                                 gint64 *buffering_left);

Extracts the buffering stats values from query .

Parameters

query

A valid GstQuery of type GST_QUERY_BUFFERING.

 

mode

a buffering mode, or NULL.

[out][allow-none]

avg_in

the average input rate, or NULL.

[out][allow-none]

avg_out

the average output rat, or NULLe.

[out][allow-none]

buffering_left

amount of buffering time left, or NULL.

[out][allow-none]

Since: 0.10.20


gst_query_set_buffering_range ()

void
gst_query_set_buffering_range (GstQuery *query,
                               GstFormat format,
                               gint64 start,
                               gint64 stop,
                               gint64 estimated_total);

Set the available query result fields in query .

Parameters

query

a GstQuery

 

format

the format to set for the start and stop values

 

start

the start to set

 

stop

the stop to set

 

estimated_total

estimated total amount of download time

 

Since: 0.10.20


gst_query_parse_buffering_range ()

void
gst_query_parse_buffering_range (GstQuery *query,
                                 GstFormat *format,
                                 gint64 *start,
                                 gint64 *stop,
                                 gint64 *estimated_total);

Parse an available query, writing the format into format , and other results into the passed parameters, if the respective parameters are non-NULL

Parameters

query

a GST_QUERY_BUFFERING type query GstQuery

 

format

the format to set for the segment_start and segment_end values, or NULL.

[out][allow-none]

start

the start to set, or NULL.

[out][allow-none]

stop

the stop to set, or NULL.

[out][allow-none]

estimated_total

estimated total amount of download time, or NULL.

[out][allow-none]

Since: 0.10.20


gst_query_add_buffering_range ()

gboolean
gst_query_add_buffering_range (GstQuery *query,
                               gint64 start,
                               gint64 stop);

Set the buffering-ranges array field in query . The current last start position of the array should be inferior to start .

Parameters

query

a GST_QUERY_BUFFERING type query GstQuery

 

start

start position of the range

 

stop

stop position of the range

 

Returns

a gboolean indicating if the range was added or not.

Since: 0.10.31


gst_query_get_n_buffering_ranges ()

guint
gst_query_get_n_buffering_ranges (GstQuery *query);

Retrieve the number of values currently stored in the buffered-ranges array of the query's structure.

Parameters

query

a GST_QUERY_BUFFERING type query GstQuery

 

Returns

the range array size as a guint.

Since: 0.10.31


gst_query_parse_nth_buffering_range ()

gboolean
gst_query_parse_nth_buffering_range (GstQuery *query,
                                     guint index,
                                     gint64 *start,
                                     gint64 *stop);

Parse an available query and get the start and stop values stored at the index of the buffered ranges array.

Parameters

query

a GST_QUERY_BUFFERING type query GstQuery

 

index

position in the buffered-ranges array to read

 

start

the start position to set, or NULL.

[out][allow-none]

stop

the stop position to set, or NULL.

[out][allow-none]

Returns

a gboolean indicating if the parsing succeeded.

Since: 0.10.31


gst_query_new_uri ()

GstQuery *
gst_query_new_uri (void);

Constructs a new query URI query object. Use gst_query_unref() when done with it. An URI query is used to query the current URI that is used by the source or sink.

Free-function: gst_query_unref

Returns

a new GstQuery.

[transfer full]

Since: 0.10.22


gst_query_parse_uri ()

void
gst_query_parse_uri (GstQuery *query,
                     gchar **uri);

Parse an URI query, writing the URI into uri as a newly allocated string, if the respective parameters are non-NULL. Free the string with g_free() after usage.

Parameters

query

a GstQuery

 

uri

the storage for the current URI (may be NULL).

[out callee-allocates][allow-none]

Since: 0.10.22


gst_query_set_uri ()

void
gst_query_set_uri (GstQuery *query,
                   const gchar *uri);

Answer a URI query by setting the requested URI.

Parameters

query

a GstQuery with query type GST_QUERY_URI

 

uri

the URI to set

 

Since: 0.10.22

Types and Values

struct GstQuery

struct GstQuery {
  GstMiniObject mini_object;

  GstQueryType type;

  GstStructure *structure;
};

The GstQuery structure.

Members

GstMiniObject mini_object;

The parent GstMiniObject type

 

GstQueryType type;

the GstQueryType

 

GstStructure *structure;

the GstStructure containing the query details.

 

enum GstQueryType

Standard predefined Query types

Members

GST_QUERY_NONE

invalid query type

 

GST_QUERY_POSITION

current position in stream

 

GST_QUERY_DURATION

total duration of the stream

 

GST_QUERY_LATENCY

latency of stream

 

GST_QUERY_JITTER

current jitter of stream

 

GST_QUERY_RATE

current rate of the stream

 

GST_QUERY_SEEKING

seeking capabilities

 

GST_QUERY_SEGMENT

segment start/stop positions

 

GST_QUERY_CONVERT

convert values between formats

 

GST_QUERY_FORMATS

query supported formats for convert

 

GST_QUERY_BUFFERING

query available media for efficient seeking. Since 0.10.20.

 

GST_QUERY_CUSTOM

a custom application or element defined query. Since 0.10.22.

 

GST_QUERY_URI

query the URI of the source or sink. Since 0.10.22.

 

struct GstQueryTypeDefinition

struct GstQueryTypeDefinition {
  GstQueryType   value;
  const gchar   *nick;
  const gchar   *description;
  GQuark         quark;
};

A Query Type definition

Members

GstQueryType value;

the unique id of the Query type

 

const gchar *nick;

a short nick

 

const gchar *description;

a longer description of the query type

 

GQuark quark;

the quark for the nick

 

enum GstBufferingMode

The different types of buffering methods.

Members

GST_BUFFERING_STREAM

a small amount of data is buffered

 

GST_BUFFERING_DOWNLOAD

the stream is being downloaded

 

GST_BUFFERING_TIMESHIFT

the stream is being downloaded in a ringbuffer

 

GST_BUFFERING_LIVE

the stream is a live stream

 

See Also

GstPad, GstElement