| GStreamer 0.10 Core Reference Manual | ||||
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| Top | Description | ||||
GstQueryGstQuery — Dynamically register new query types. Provide functions to create queries, and to set and parse values in them. |
#include <gst/gst.h>
GstQuery;
enum GstQueryType;
#define GST_QUERY_TYPE_NAME (query)
GstQueryTypeDefinition;
const gchar* gst_query_type_get_name (GstQueryType query);
GQuark gst_query_type_to_quark (GstQueryType query);
GstQueryType gst_query_type_register (const gchar *nick,
const gchar *description);
GstQueryType gst_query_type_get_by_nick (const gchar *nick);
gboolean gst_query_types_contains (const GstQueryType *types,
GstQueryType type);
const GstQueryTypeDefinition * gst_query_type_get_details
(GstQueryType type);
GstIterator* gst_query_type_iterate_definitions (void);
GstQuery * gst_query_ref (GstQuery *q);
void gst_query_unref (GstQuery *q);
GstQuery * gst_query_copy (const GstQuery *q);
#define gst_query_make_writable (q)
GstQuery * gst_query_new_application (GstQueryType type,
GstStructure *structure);
GstStructure * gst_query_get_structure (GstQuery *query);
GstQuery* gst_query_new_convert (GstFormat src_format,
gint64 value,
GstFormat dest_format);
void gst_query_set_convert (GstQuery *query,
GstFormat src_format,
gint64 src_value,
GstFormat dest_format,
gint64 dest_value);
void gst_query_parse_convert (GstQuery *query,
GstFormat *src_format,
gint64 *src_value,
GstFormat *dest_format,
gint64 *dest_value);
GstQuery* gst_query_new_position (GstFormat format);
void gst_query_set_position (GstQuery *query,
GstFormat format,
gint64 cur);
void gst_query_parse_position (GstQuery *query,
GstFormat *format,
gint64 *cur);
GstQuery* gst_query_new_duration (GstFormat format);
void gst_query_set_duration (GstQuery *query,
GstFormat format,
gint64 duration);
void gst_query_parse_duration (GstQuery *query,
GstFormat *format,
gint64 *duration);
GstQuery* gst_query_new_latency (void);
void gst_query_parse_latency (GstQuery *query,
gboolean *live,
GstClockTime *min_latency,
GstClockTime *max_latency);
void gst_query_set_latency (GstQuery *query,
gboolean live,
GstClockTime min_latency,
GstClockTime max_latency);
GstQuery* gst_query_new_seeking (GstFormat format);
void gst_query_set_seeking (GstQuery *query,
GstFormat format,
gboolean seekable,
gint64 segment_start,
gint64 segment_end);
void gst_query_parse_seeking (GstQuery *query,
GstFormat *format,
gboolean *seekable,
gint64 *segment_start,
gint64 *segment_end);
GstQuery* gst_query_new_formats (void);
void gst_query_set_formats (GstQuery *query,
gint n_formats,
...);
void gst_query_set_formatsv (GstQuery *query,
gint n_formats,
GstFormat *formats);
void gst_query_parse_formats_length (GstQuery *query,
guint *n_formats);
void gst_query_parse_formats_nth (GstQuery *query,
guint nth,
GstFormat *format);
GstQuery* gst_query_new_segment (GstFormat format);
void gst_query_set_segment (GstQuery *query,
gdouble rate,
GstFormat format,
gint64 start_value,
gint64 stop_value);
void gst_query_parse_segment (GstQuery *query,
gdouble *rate,
GstFormat *format,
gint64 *start_value,
gint64 *stop_value);
enum GstBufferingMode;
GstQuery* gst_query_new_buffering (GstFormat format);
void gst_query_set_buffering_percent (GstQuery *query,
gboolean busy,
gint percent);
void gst_query_parse_buffering_percent (GstQuery *query,
gboolean *busy,
gint *percent);
void gst_query_set_buffering_stats (GstQuery *query,
GstBufferingMode mode,
gint avg_in,
gint avg_out,
gint64 buffering_left);
void gst_query_parse_buffering_stats (GstQuery *query,
GstBufferingMode *mode,
gint *avg_in,
gint *avg_out,
gint64 *buffering_left);
void gst_query_set_buffering_range (GstQuery *query,
GstFormat format,
gint64 start,
gint64 stop,
gint64 estimated_total);
void gst_query_parse_buffering_range (GstQuery *query,
GstFormat *format,
gint64 *start,
gint64 *stop,
gint64 *estimated_total);
GstQuery * gst_query_new_uri (void);
void gst_query_parse_uri (GstQuery *query,
gchar **uri);
void gst_query_set_uri (GstQuery *query,
const gchar *uri);
GstQuery functions are used to register a new query types to the gstreamer core. Query types can be used to perform queries on pads and elements.
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
1 2 3 4 5 6 7 8 9 10 11 12 13 |
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)
typedef struct {
GstMiniObject mini_object;
GstQueryType type;
GstStructure *structure;
} GstQuery;
The GstQuery structure.
GstMiniObject |
The parent GstMiniObject type |
GstQueryType |
the GstQueryType |
GstStructure * |
the GstStructure containing the query details. |
typedef enum {
GST_QUERY_NONE = 0,
GST_QUERY_POSITION,
GST_QUERY_DURATION,
GST_QUERY_LATENCY,
GST_QUERY_JITTER, /* not in draft-query, necessary? */
GST_QUERY_RATE,
GST_QUERY_SEEKING,
GST_QUERY_SEGMENT,
GST_QUERY_CONVERT,
GST_QUERY_FORMATS,
GST_QUERY_BUFFERING,
GST_QUERY_CUSTOM,
GST_QUERY_URI
} GstQueryType;
Standard predefined Query types
| invalid query type | |
| current position in stream | |
| total duration of the stream | |
| latency of stream | |
| current jitter of stream | |
| current rate of the stream | |
| seeking capabilities | |
| segment start/stop positions | |
| convert values between formats | |
| query supported formats for convert | |
| query available media for efficient seeking. Since 0.10.20. | |
| a custom application or element defined query. Since 0.10.22. | |
| query the URI of the source or sink. Since 0.10.22. |
#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.
|
the query to query |
Since 0.10.4
typedef struct {
GstQueryType value;
gchar *nick;
gchar *description;
GQuark quark;
} GstQueryTypeDefinition;
A Query Type definition
GstQueryType |
the unique id of the Query type |
gchar * |
a short nick |
gchar * |
a longer description of the query type |
GQuark |
the quark for the nick |
const gchar* gst_query_type_get_name (GstQueryType query);
Get a printable name for the given query type. Do not modify or free.
|
the query type |
Returns : |
a reference to the static name of the query. |
GQuark gst_query_type_to_quark (GstQueryType query);
Get the unique quark for the given query type.
|
the query type |
Returns : |
the quark associated with the query type |
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
|
The nick of the new query |
|
The description of the new query |
Returns : |
A new GstQueryType or an already registered query with the same nick. |
GstQueryType gst_query_type_get_by_nick (const gchar *nick);
Get the query type registered with nick.
|
The nick of the query |
Returns : |
The query registered with nick or GST_QUERY_NONE
if the query was not registered.
|
gboolean gst_query_types_contains (const GstQueryType *types, GstQueryType type);
See if the given GstQueryType is inside the types query types array.
|
The query array to search |
|
the GstQueryType to find |
Returns : |
TRUE if the type is found inside the array |
const GstQueryTypeDefinition * gst_query_type_get_details (GstQueryType type);
Get details about the given GstQueryType.
|
a GstQueryType |
Returns : |
The GstQueryTypeDefinition for type or NULL on failure.
|
GstIterator* gst_query_type_iterate_definitions (void);
Get a GstIterator of all the registered query types. The definitions iterated over are read only.
Returns : |
A GstIterator of GstQueryTypeDefinition. |
GstQuery * gst_query_ref (GstQuery *q);
Increases the refcount of the given query by one.
|
a GstQuery to increase the refcount of. |
Returns : |
q
|
void gst_query_unref (GstQuery *q);
Decreases the refcount of the query. If the refcount reaches 0, the query will be freed.
|
a GstQuery to decrease the refcount of. |
GstQuery * gst_query_copy (const GstQuery *q);
Copies the given query using the copy function of the parent GstStructure.
|
a GstQuery to copy. |
Returns : |
a new copy of q.
|
#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.
|
a GstQuery to make writable |
GstQuery * gst_query_new_application (GstQueryType type, GstStructure *structure);
Constructs a new custom application query object. Use gst_query_unref()
when done with it.
|
the query type |
|
a structure for the query |
Returns : |
a GstQuery |
GstStructure * gst_query_get_structure (GstQuery *query);
Get the structure of a 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. |
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.
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.
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.
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.
void gst_query_set_position (GstQuery *query, GstFormat format, gint64 cur);
Answer a position query by setting the requested value in the given format.
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.
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.
void gst_query_set_duration (GstQuery *query, GstFormat format, gint64 duration);
Answer a duration query by setting the requested value in the given format.
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.
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.
Returns : |
A GstQuery |
Since 0.10.12
void gst_query_parse_latency (GstQuery *query, gboolean *live, GstClockTime *min_latency, GstClockTime *max_latency);
Parse a latency query answer.
|
a GstQuery |
|
storage for live or NULL |
|
the storage for the min latency or NULL |
|
the storage for the max latency or NULL |
Since 0.10.12
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.
|
a GstQuery |
|
if there is a live element upstream |
|
the minimal latency of the live element |
|
the maximal latency of the live element |
Since 0.10.12
GstQuery* gst_query_new_seeking (GstFormat format);
Constructs a new query object for querying seeking properties of the stream.
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.
|
a GstQuery |
|
the format to set for the segment_start and segment_end values
|
|
the seekable flag to set |
|
the segment_start to set |
|
the segment_end to set |
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
|
a GST_QUERY_SEEKING type query GstQuery |
|
the format to set for the segment_start and segment_end values
|
|
the seekable flag to set |
|
the segment_start to set |
|
the segment_end to set |
GstQuery* gst_query_new_formats (void);
Constructs a new query object for querying formats of the stream.
Returns : |
A GstQuery |
Since 0.10.4
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.
|
a GstQuery |
|
the number of formats to set. |
|
A number of GstFormats equal to n_formats.
|
void gst_query_set_formatsv (GstQuery *query, gint n_formats, 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.
|
a GstQuery |
|
the number of formats to set. |
|
An array containing n_formats GstFormat values.
|
Since 0.10.4
void gst_query_parse_formats_length (GstQuery *query, guint *n_formats);
Parse the number of formats in the formats query.
|
a GstQuery |
|
the number of formats in this query. |
Since 0.10.4
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.
|
a GstQuery |
|
the nth format to retrieve. |
|
a pointer to store the nth format |
Since 0.10.4
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.
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.
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.
typedef enum {
GST_BUFFERING_STREAM,
GST_BUFFERING_DOWNLOAD,
GST_BUFFERING_TIMESHIFT,
GST_BUFFERING_LIVE
} GstBufferingMode;
The different types of buffering methods.
GstQuery* gst_query_new_buffering (GstFormat format);
Constructs a new query object for querying the buffering status of a stream.
Since 0.10.20
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.
|
A valid GstQuery of type GST_QUERY_BUFFERING. |
|
if buffering is busy |
|
a buffering percent |
Since 0.10.20
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.
|
A valid GstQuery of type GST_QUERY_BUFFERING. |
|
if buffering is busy |
|
a buffering percent |
Since 0.10.20
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.
|
A valid GstQuery of type GST_QUERY_BUFFERING. |
|
a buffering mode |
|
the average input rate |
|
the average output rate |
|
amount of buffering time left |
Since 0.10.20
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.
|
A valid GstQuery of type GST_QUERY_BUFFERING. |
|
a buffering mode |
|
the average input rate |
|
the average output rate |
|
amount of buffering time left |
Since 0.10.20
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.
|
a GstQuery |
|
the format to set for the start and stop values
|
|
the start to set |
|
the stop to set |
|
estimated total amount of download time |
Since 0.10.20
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
|
a GST_QUERY_SEEKING type query GstQuery |
|
the format to set for the segment_start and segment_end values
|
|
the start to set |
|
the stop to set |
|
estimated total amount of download time |
Since 0.10.20
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.
Returns : |
A GstQuery |
Since 0.10.22
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.
|
a GstQuery |
|
the storage for the current URI (may be NULL) |
Since 0.10.22