Increase the av_log() levels, and add some documentation for them

Originally committed as revision 7614 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/log.h

@@ -38,10 +38,49 @@ struct AVCLASS {
 
 /* av_log API */
 
+#if LIBAVUTIL_VERSION_INT < (50<<16)
 #define AV_LOG_QUIET -1
+#define AV_LOG_FATAL 0
 #define AV_LOG_ERROR 0
+#define AV_LOG_WARNING 1
 #define AV_LOG_INFO 1
+#define AV_LOG_VERBOSE 1
 #define AV_LOG_DEBUG 2
+#else
+#define AV_LOG_QUIET    -8
+
+/**
+ * something went really wrong and we will crash now
+ */
+#define AV_LOG_PANIC     0
+
+/**
+ * something went wrong and recovery is not possible
+ * like no header in a format which depends on it or a combination
+ * of parameters which are not allowed
+ */
+#define AV_LOG_FATAL     8
+
+/**
+ * something went wrong and cannot losslessly be recovered
+ * but not all future data is affected
+ */
+#define AV_LOG_ERROR    16
+
+/**
+ * something somehow does not look correct / something which may or may not
+ * lead to some problems like use of -vstrict -2
+ */
+#define AV_LOG_WARNING  24
+
+#define AV_LOG_INFO     32
+#define AV_LOG_VERBOSE  40
+
+/**
+ * stuff which is only useful for libav* developers
+ */
+#define AV_LOG_DEBUG    48
+#endif
 extern int av_log_level;
 
 #ifdef __GNUC__