doxy: provide a start page and document libavutil

Introduce a basic layout, the subpages are currently left empty.

Split libavutil in multiple groups as example of the structure

libavutil/avutil.h

@@ -26,6 +26,95 @@
  * external API header
  */
 
+/**
+ * @mainpage
+ *
+ * @section libav_intro Introduction
+ *
+ * This document describe the usage of the different libraries
+ * provided by Libav.
+ *
+ * @li @subpage libavcodec  encoding/decoding library
+ * @li @subpage libavfilter graph based frame editing library
+ * @li @subpage libavformat I/O and muxing/demuxing library
+ * @li @ref lavu "libavutil" common utility library
+ * @li @subpage libpostproc post processing library
+ * @li @subpage libswscale  color conversion and scaling library
+ *
+ */
+
+/**
+ * @defgroup lavu Common utility functions
+ *
+ * @brief
+ * libavutil contains the code shared across all the other Libav
+ * libraries
+ *
+ * @note In order to use the functions provided by avutil you must include
+ * the specific header.
+ *
+ * @{
+ *
+ * @defgroup lavu_crypto Crypto and Hashing
+ *
+ * @{
+ * @}
+ *
+ * @defgroup lavu_math Maths
+ * @{
+ *
+ * @}
+ *
+ * @defgroup lavu_string String Manipulation
+ *
+ * @{
+ *
+ * @}
+ *
+ * @defgroup lavu_mem Memory Management
+ *
+ * @{
+ *
+ * @}
+ *
+ * @defgroup lavu_data Data Structures
+ * @{
+ *
+ * @}
+ *
+ * @defgroup lavu_audio Audio related
+ *
+ * @{
+ *
+ * @}
+ *
+ * @defgroup lavu_error Error Codes
+ *
+ * @{
+ *
+ * @}
+ *
+ * @defgroup lavu_misc Other
+ *
+ * @{
+ *
+ * @defgroup lavu_internal Internal
+ *
+ * Not exported functions, for internal usage only
+ *
+ * @{
+ *
+ * @}
+ */
+
+
+/**
+ * @defgroup preproc_misc Preprocessor String Macros
+ *
+ * String manipulation macros
+ *
+ * @{
+ */
 
 #define AV_STRINGIFY(s)         AV_TOSTRING(s)
 #define AV_TOSTRING(s) #s
@@ -35,10 +124,34 @@
 
 #define AV_PRAGMA(s) _Pragma(#s)
 
+/**
+ * @}
+ */
+
+/**
+ * @defgroup version_utils Library Version Macros
+ *
+ * Useful to check and match library version in order to maintain
+ * backward compatibility.
+ *
+ * @{
+ */
+
 #define AV_VERSION_INT(a, b, c) (a<<16 | b<<8 | c)
 #define AV_VERSION_DOT(a, b, c) a ##.## b ##.## c
 #define AV_VERSION(a, b, c) AV_VERSION_DOT(a, b, c)
 
+/**
+ * @}
+ *
+ * @defgroup lavu_ver Version and Build diagnostics
+ *
+ * Macros and function useful to check at compiletime and at runtime
+ * which version of libavutil is in use.
+ *
+ * @{
+ */
+
 #define LIBAVUTIL_VERSION_MAJOR 51
 #define LIBAVUTIL_VERSION_MINOR 16
 #define LIBAVUTIL_VERSION_MICRO  0
@@ -54,8 +167,16 @@
 #define LIBAVUTIL_IDENT         "Lavu" AV_STRINGIFY(LIBAVUTIL_VERSION)
 
 /**
+ * @}
+ *
+ * @defgroup depr_guards Deprecation guards
  * Those FF_API_* defines are not part of public API.
  * They may change, break or disappear at any time.
+ *
+ * They are used mostly internally to mark code that will be removed
+ * on the next major version.
+ *
+ * @{
  */
 #ifndef FF_API_GET_BITS_PER_SAMPLE_FMT
 #define FF_API_GET_BITS_PER_SAMPLE_FMT (LIBAVUTIL_VERSION_MAJOR < 52)
@@ -70,6 +191,15 @@
 #define FF_API_OLD_AVOPTIONS            (LIBAVUTIL_VERSION_MAJOR < 52)
 #endif
 
+/**
+ * @}
+ */
+
+/**
+ * @addtogroup lavu_ver
+ * @{
+ */
+
 /**
  * Return the LIBAVUTIL_VERSION_INT constant.
  */
@@ -85,16 +215,35 @@ const char *avutil_configuration(void);
  */
 const char *avutil_license(void);
 
+/**
+ * @}
+ */
+
+/**
+ * @addtogroup lavu_media Media Type
+ * @brief Media Type
+ */
+
 enum AVMediaType {
-    AVMEDIA_TYPE_UNKNOWN = -1,
+    AVMEDIA_TYPE_UNKNOWN = -1,  ///< Usually treated as AVMEDIA_TYPE_DATA
     AVMEDIA_TYPE_VIDEO,
     AVMEDIA_TYPE_AUDIO,
-    AVMEDIA_TYPE_DATA,
+    AVMEDIA_TYPE_DATA,          ///< Opaque data information usually continuous
     AVMEDIA_TYPE_SUBTITLE,
-    AVMEDIA_TYPE_ATTACHMENT,
+    AVMEDIA_TYPE_ATTACHMENT,    ///< Opaque data information usually sparse
     AVMEDIA_TYPE_NB
 };
 
+/**
+ * @defgroup lavu_const Constants
+ * @{
+ *
+ * @defgroup lavu_enc Encoding specific
+ *
+ * @note those definition should move to avcodec
+ * @{
+ */
+
 #define FF_LAMBDA_SHIFT 7
 #define FF_LAMBDA_SCALE (1<<FF_LAMBDA_SHIFT)
 #define FF_QP2LAMBDA 118 ///< factor to convert from H.263 QP to lambda
@@ -102,10 +251,46 @@ enum AVMediaType {
 
 #define FF_QUALITY_SCALE FF_LAMBDA_SCALE //FIXME maybe remove
 
+/**
+ * @}
+ * @defgroup lavu_time Timestamp specific
+ *
+ * Libav internal timebase and timestamp definitions
+ *
+ * @{
+ */
+
+/**
+ * @brief Undefined timestamp value
+ *
+ * Usually reported by demuxer that work on containers that do not provide
+ * either pts or dts.
+ */
+
 #define AV_NOPTS_VALUE          INT64_C(0x8000000000000000)
+
+/**
+ * Internal time base represented as integer
+ */
+
 #define AV_TIME_BASE            1000000
+
+/**
+ * Internal time base represented as fractional value
+ */
+
 #define AV_TIME_BASE_Q          (AVRational){1, AV_TIME_BASE}
 
+/**
+ * @}
+ * @}
+ * @defgroup lavu_picture Image related
+ *
+ * AVPicture types, pixel formats and basic image planes manipulation.
+ *
+ * @{
+ */
+
 enum AVPictureType {
     AV_PICTURE_TYPE_I = 1, ///< Intra
     AV_PICTURE_TYPE_P,     ///< Predicted
@@ -125,7 +310,16 @@ enum AVPictureType {
  */
 char av_get_picture_type_char(enum AVPictureType pict_type);
 
+/**
+ * @}
+ */
+
 #include "common.h"
 #include "error.h"
 
+/**
+ * @}
+ * @}
+ */
+
 #endif /* AVUTIL_AVUTIL_H */