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GStreamer 0.10 Core Reference Manual | |
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#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);
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 10. 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)
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.
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, ...)
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.
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_DECRYPT,
GST_STREAM_ERROR_DECRYPT_NOKEY,
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, ...
#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.
#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.
#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.
#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.
#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.
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. |