GstGError

GstGError — Categorized error messages

Synopsis


#include <gst/gst.h>


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
gchar*              gst_error_get_message               (GQuark domain,
                                                         gint code);


Description

GStreamer elements can throw non-fatal warnings and fatal errors. Higher-level elements and applications can programatically 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 7. Throwing an error

    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.

Last reviewed on 2006-09-15 (0.10.10)

Details

enum GstCoreError

typedef enum
{
  GST_CORE_ERROR_FAILED = 1,
  GST_CORE_ERROR_TOO_LAZY,
  GST_CORE_ERROR_NOT_IMPLEMENTED,
  GST_CORE_ERROR_STATE_CHANGE,
  GST_CORE_ERROR_PAD,
  GST_CORE_ERROR_THREAD,
  GST_CORE_ERROR_NEGOTIATION,
  GST_CORE_ERROR_EVENT,
  GST_CORE_ERROR_SEEK,
  GST_CORE_ERROR_CAPS,
  GST_CORE_ERROR_TAG,
  GST_CORE_ERROR_MISSING_PLUGIN,
  GST_CORE_ERROR_CLOCK,
  GST_CORE_ERROR_DISABLED,
  GST_CORE_ERROR_NUM_ERRORS
} GstCoreError;

Core errors are errors inside the core GStreamer library.

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 (Since: 0.10.13).
GST_CORE_ERROR_NUM_ERRORS the number of core error types.

enum GstLibraryError

typedef enum
{
  GST_LIBRARY_ERROR_FAILED = 1,
  GST_LIBRARY_ERROR_TOO_LAZY,
  GST_LIBRARY_ERROR_INIT,
  GST_LIBRARY_ERROR_SHUTDOWN,
  GST_LIBRARY_ERROR_SETTINGS,
  GST_LIBRARY_ERROR_ENCODE,
  GST_LIBRARY_ERROR_NUM_ERRORS
} GstLibraryError;

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

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

typedef enum
{
  GST_RESOURCE_ERROR_FAILED = 1,
  GST_RESOURCE_ERROR_TOO_LAZY,
  GST_RESOURCE_ERROR_NOT_FOUND,
  GST_RESOURCE_ERROR_BUSY,
  GST_RESOURCE_ERROR_OPEN_READ,
  GST_RESOURCE_ERROR_OPEN_WRITE,
  GST_RESOURCE_ERROR_OPEN_READ_WRITE,
  GST_RESOURCE_ERROR_CLOSE,
  GST_RESOURCE_ERROR_READ,
  GST_RESOURCE_ERROR_WRITE,
  GST_RESOURCE_ERROR_SEEK,
  GST_RESOURCE_ERROR_SYNC,
  GST_RESOURCE_ERROR_SETTINGS,
  GST_RESOURCE_ERROR_NO_SPACE_LEFT,
  GST_RESOURCE_ERROR_NUM_ERRORS
} 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.

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_NUM_ERRORS the number of resource error types.

enum GstStreamError

typedef enum
{
  GST_STREAM_ERROR_FAILED = 1,
  GST_STREAM_ERROR_TOO_LAZY,
  GST_STREAM_ERROR_NOT_IMPLEMENTED,
  GST_STREAM_ERROR_TYPE_NOT_FOUND,
  GST_STREAM_ERROR_WRONG_TYPE,
  GST_STREAM_ERROR_CODEC_NOT_FOUND,
  GST_STREAM_ERROR_DECODE,
  GST_STREAM_ERROR_ENCODE,
  GST_STREAM_ERROR_DEMUX,
  GST_STREAM_ERROR_MUX,
  GST_STREAM_ERROR_FORMAT,
  GST_STREAM_ERROR_NUM_ERRORS
} 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, ...

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_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.


gst_error_get_message ()

gchar*              gst_error_get_message               (GQuark domain,
                                                         gint code);

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

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 the current locale.

See Also

GstMessage