GstGError: GStreamer 1.0 Core Reference Manual

GstGError

GstGError — Categorized error messages

Functions

Types and Values

enum	GstCoreError
enum	GstLibraryError
enum	GstResourceError
enum	GstStreamError
#define	GST_CORE_ERROR
#define	GST_LIBRARY_ERROR
#define	GST_RESOURCE_ERROR
#define	GST_STREAM_ERROR
#define	GST_ERROR_SYSTEM

Includes

#include <gst/gst.h>

Description

GStreamer elements can throw non-fatal warnings and fatal errors. Higher-level elements and applications can programmatically filter the ones they are interested in or can recover from, and have a default handler handle the rest of them.

The rest of this section will use the term “error” to mean both (non-fatal) warnings and (fatal) errors; they are treated similarly.

Errors from elements are the combination of a GError and a debug string. The GError contains:

a domain type: CORE, LIBRARY, RESOURCE or STREAM
a code: an enum value specific to the domain
a translated, human-readable message
a non-translated additional debug string, which also contains
file and line information

Elements do not have the context required to decide what to do with errors. As such, they should only inform about errors, and stop their processing. In short, an element doesn't know what it is being used for.

It is the application or compound element using the given element that has more context about the use of the element. Errors can be received by listening to the GstBus of the element/pipeline for GstMessage objects with the type GST_MESSAGE_ERROR or GST_MESSAGE_WARNING. The thrown errors should be inspected, and filtered if appropriate.

An application is expected to, by default, present the user with a dialog box (or an equivalent) showing the error message. The dialog should also allow a way to get at the additional debug information, so the user can provide bug reporting information.

A compound element is expected to forward errors by default higher up the hierarchy; this is done by default in the same way as for other types of GstMessage.

When applications or compound elements trigger errors that they can recover from, they can filter out these errors and take appropriate action. For example, an application that gets an error from xvimagesink that indicates all XVideo ports are taken, the application can attempt to use another sink instead.

Elements throw errors using the GST_ELEMENT_ERROR convenience macro:

Example 5. Throwing an error

1 2	GST_ELEMENT_ERROR (src, RESOURCE, NOT_FOUND, (_("No file name specified for reading.")), (NULL));

Things to keep in mind:

Don't go off inventing new error codes. The ones currently provided should be enough. If you find your type of error does not fit the current codes, you should use FAILED.
Don't provide a message if the default one suffices. this keeps messages more uniform. Use (NULL) - not forgetting the parentheses.
If you do supply a custom message, it should be marked for translation. The message should start with a capital and end with a period. The message should describe the error in short, in a human-readable form, and without any complex technical terms. A user interface will present this message as the first thing a user sees. Details, technical info, ... should go in the debug string.
The debug string can be as you like. Again, use (NULL) if there's nothing to add - file and line number will still be passed. GST_ERROR_SYSTEM can be used as a shortcut to give debug information on a system call error.

Functions

gst_error_get_message ()

gchar *
gst_error_get_message (GQuark domain,
                       gint code);

Get a string describing the error message in the current locale.

Parameters

domain	the GStreamer error domain this error belongs to.
code	the error code belonging to the domain.

Returns

a newly allocated string describing the error message (in UTF-8 encoding).

[transfer full]

Types and Values

enum GstCoreError

Core errors are errors inside the core GStreamer library.

Members

GST_CORE_ERROR_FAILED	a general error which doesn't fit in any other category. Make sure you add a custom message to the error call.
GST_CORE_ERROR_TOO_LAZY	do not use this except as a placeholder for deciding where to go while developing code.
GST_CORE_ERROR_NOT_IMPLEMENTED	use this when you do not want to implement this functionality yet.
GST_CORE_ERROR_STATE_CHANGE	used for state change errors.
GST_CORE_ERROR_PAD	used for pad-related errors.
GST_CORE_ERROR_THREAD	used for thread-related errors.
GST_CORE_ERROR_NEGOTIATION	used for negotiation-related errors.
GST_CORE_ERROR_EVENT	used for event-related errors.
GST_CORE_ERROR_SEEK	used for seek-related errors.
GST_CORE_ERROR_CAPS	used for caps-related errors.
GST_CORE_ERROR_TAG	used for negotiation-related errors.
GST_CORE_ERROR_MISSING_PLUGIN	used if a plugin is missing.
GST_CORE_ERROR_CLOCK	used for clock related errors.
GST_CORE_ERROR_DISABLED	used if functionality has been disabled at compile time.
GST_CORE_ERROR_NUM_ERRORS	the number of core error types.

enum GstLibraryError

Library errors are for errors from the library being used by elements (initializing, finalizing, settings, ...)

Members

GST_LIBRARY_ERROR_FAILED	a general error which doesn't fit in any other category. Make sure you add a custom message to the error call.
GST_LIBRARY_ERROR_TOO_LAZY	do not use this except as a placeholder for deciding where to go while developing code.
GST_LIBRARY_ERROR_INIT	used when the library could not be opened.
GST_LIBRARY_ERROR_SHUTDOWN	used when the library could not be closed.
GST_LIBRARY_ERROR_SETTINGS	used when the library doesn't accept settings.
GST_LIBRARY_ERROR_ENCODE	used when the library generated an encoding error.
GST_LIBRARY_ERROR_NUM_ERRORS	the number of library error types.

enum GstResourceError

Resource errors are for any resource used by an element: memory, files, network connections, process space, ... They're typically used by source and sink elements.

Members

GST_RESOURCE_ERROR_FAILED	a general error which doesn't fit in any other category. Make sure you add a custom message to the error call.
GST_RESOURCE_ERROR_TOO_LAZY	do not use this except as a placeholder for deciding where to go while developing code.
GST_RESOURCE_ERROR_NOT_FOUND	used when the resource could not be found.
GST_RESOURCE_ERROR_BUSY	used when resource is busy.
GST_RESOURCE_ERROR_OPEN_READ	used when resource fails to open for reading.
GST_RESOURCE_ERROR_OPEN_WRITE	used when resource fails to open for writing.
GST_RESOURCE_ERROR_OPEN_READ_WRITE	used when resource cannot be opened for both reading and writing, or either (but unspecified which).
GST_RESOURCE_ERROR_CLOSE	used when the resource can't be closed.
GST_RESOURCE_ERROR_READ	used when the resource can't be read from.
GST_RESOURCE_ERROR_WRITE	used when the resource can't be written to.
GST_RESOURCE_ERROR_SEEK	used when a seek on the resource fails.
GST_RESOURCE_ERROR_SYNC	used when a synchronize on the resource fails.
GST_RESOURCE_ERROR_SETTINGS	used when settings can't be manipulated on.
GST_RESOURCE_ERROR_NO_SPACE_LEFT	used when the resource has no space left.
GST_RESOURCE_ERROR_NOT_AUTHORIZED	used when the resource can't be opened due to missing authorization. (Since 1.2.4)
GST_RESOURCE_ERROR_NUM_ERRORS	the number of resource error types.

enum GstStreamError

Stream errors are for anything related to the stream being processed: format errors, media type errors, ... They're typically used by decoders, demuxers, converters, ...

Members

GST_STREAM_ERROR_FAILED	a general error which doesn't fit in any other category. Make sure you add a custom message to the error call.
GST_STREAM_ERROR_TOO_LAZY	do not use this except as a placeholder for deciding where to go while developing code.
GST_STREAM_ERROR_NOT_IMPLEMENTED	use this when you do not want to implement this functionality yet.
GST_STREAM_ERROR_TYPE_NOT_FOUND	used when the element doesn't know the stream's type.
GST_STREAM_ERROR_WRONG_TYPE	used when the element doesn't handle this type of stream.
GST_STREAM_ERROR_CODEC_NOT_FOUND	used when there's no codec to handle the stream's type.
GST_STREAM_ERROR_DECODE	used when decoding fails.
GST_STREAM_ERROR_ENCODE	used when encoding fails.
GST_STREAM_ERROR_DEMUX	used when demuxing fails.
GST_STREAM_ERROR_MUX	used when muxing fails.
GST_STREAM_ERROR_FORMAT	used when the stream is of the wrong format (for example, wrong caps).
GST_STREAM_ERROR_DECRYPT	used when the stream is encrypted and can't be decrypted because this is not supported by the element.
GST_STREAM_ERROR_DECRYPT_NOKEY	used when the stream is encrypted and can't be decrypted because no suitable key is available.
GST_STREAM_ERROR_NUM_ERRORS	the number of stream error types.

GST_CORE_ERROR

#define GST_CORE_ERROR      gst_core_error_quark ()

Error domain for core system. Errors in this domain will be from the GstCoreError enumeration. See GError for information on error domains.

GST_LIBRARY_ERROR

#define GST_LIBRARY_ERROR   gst_library_error_quark ()

Error domain for library loading. Errors in this domain will be from the GstLibraryError enumeration. See GError for information on error domains.

GST_RESOURCE_ERROR

#define GST_RESOURCE_ERROR  gst_resource_error_quark ()

Error domain for resource handling. Errors in this domain will be from the GstResourceError enumeration. See GError for information on error domains.

GST_STREAM_ERROR

#define GST_STREAM_ERROR    gst_stream_error_quark ()

Error domain for media stream processing. Errors in this domain will be from the GstStreamError enumeration. See GError for information on error domains.

GST_ERROR_SYSTEM

#define GST_ERROR_SYSTEM    ("system error: %s", g_strerror (errno))

Builds a string using errno describing the previously failed system call. To be used as the debug argument in GST_ELEMENT_ERROR.

GstGError

Functions

Types and Values

Includes

Description

Functions

gst_error_get_message ()

Parameters

Returns

Types and Values

enum GstCoreError

Members

enum GstLibraryError

Members

enum GstResourceError

Members

enum GstStreamError

Members

GST_CORE_ERROR

GST_LIBRARY_ERROR

GST_RESOURCE_ERROR

GST_STREAM_ERROR

GST_ERROR_SYSTEM

See Also