Here is a list of all modules:
[detail level 1234]
 ASS styles
 ASS functions
 end of Dialogue Event
 libavcodecEncoding/Decoding Library
 Frame parsing
 Native Codecs
 External library wrappers
 Hardware Accelerators bridge
 send/receive encoding and decoding API overviewThe avcodec_send_packet()/avcodec_receive_frame()/avcodec_send_frame()/ avcodec_receive_packet() functions provide an encode/decode API, which decouples input and output
 Core functions/structures.Basic definitions, functions for querying libavcodec capabilities, allocating core structures, etc
 AVPictureFunctions for working with AVPicture
 Utility functionsMiscellaneous utility functions related to both encoding and decoding (or neither)
 Pixel formatsFunctions for working with pixel formats
 FFT functions
 AVPacketTypes and functions for working with AVPacket
 libavdeviceSpecial devices muxing/demuxing library
 libavfilterGraph-based frame editing library
 Buffer sink APIThe buffersink and abuffersink filters are there to connect filter graphs to applications
 Buffer sink accessorsGet the properties of the stream
 Buffer source API
 libavformatI/O and Muxing/Demuxing Library
 DemuxingDemuxers read a media file and split it into chunks of data (packets)
 MuxingMuxers take encoded data in the form of AVPackets and write it into files or other output bytestreams in the specified container format
 I/O Read/Write
 Native Demuxers
 External library wrappers
 I/O Protocols
 Public Metadata APIThe metadata API allows libavformat to export metadata tags to a client application when demuxing
 Core functionsFunctions for querying libavformat capabilities, allocating core structures, etc
 Utility functionsMiscellaneous utility functions related to both muxing and demuxing (or neither)
 RIFF FourCCsGet the tables mapping RIFF FourCCs to libavcodec AVCodecIDs
 libavresampleLibavresample (lavr) is a library that handles audio resampling, sample format conversion and mixing
 libavutilCommon code shared across all FFmpeg libraries
 Crypto and Hashing
 Hash FunctionsHash functions useful in multimedia
 MathematicsMathematical utilities for working with timestamp and time base
 AVRationalRational number calculation
 String Manipulation
 Memory ManagementUtilities for manipulating memory
 Alignment MacrosHelper macros for declaring aligned variables
 Function AttributesFunction attributes applicable to memory handling functions
 Heap ManagementFunctions responsible for allocating, freeing, and copying memory
 Dynamic ArrayUtilities to make an array grow when needed
 Miscellaneous FunctionsOther functions related to memory allocation
 Data Structures
 AVBufferAVBuffer is an API for reference-counted data buffers
 AVBufferPoolAVBufferPool is an API for a lock-free thread-safe pool of AVBuffers
 AVFrameAVFrame is an abstraction for reference-counted raw multimedia data
 AVOptionsAVOptions provide a generic system to declare options on arbitrary structs ("objects")
 AVDictionarySimple key:value store
 AVTreeLow-complexity tree container
 Video related
 Display transformation matrix functionsThe display transformation matrix specifies an affine transformation that should be applied to video frames for correct presentation
 Spherical video mappingA spherical video file contains surfaces that need to be mapped onto a sphere
 Stereo3D types and functionsA stereoscopic video file consists in multiple views embedded in a single frame, usually describing two views of a scene
 Audio related
 Audio FIFO Buffer
 Audio channel masksA channel layout is a 64-bits integer with a bit set for every channel
 Audio channel layouts
 Audio downmix metadata
 Audio sample formatsAudio sample format enumeration and related convenience functions
 Samples manipulationFunctions that manipulate audio samples
 Error Codes
 Logging Facility
 Logging Constants
 Preprocessor String MacrosString manipulation macros
 Library Version MacrosUseful to check and match library version in order to maintain backward compatibility
 Image relatedAVPicture types, pixel formats and basic image planes manipulation
 Version and Build diagnosticsMacros and function useful to check at compiletime and at runtime which version of libavutil is in use
 Media TypeMedia Type
 Device context creation flagsAVHWFramesContext.hwctx is currently not used
 libpostprocVideo postprocessing library
 libswresampleAudio resampling, sample format conversion and mixing library
 libswscaleColor conversion and scaling library