Here is a list of all files with brief descriptions:

[detail level 123]

doc
examples
avio_list_dir.c
avio_read_callback.c
decode_audio.c
decode_filter_audio.c
decode_filter_video.c	API example for decoding and filtering
decode_video.c
demux_decode.c
encode_audio.c
encode_video.c
extract_mvs.c
filter_audio.c
hw_decode.c
mux.c
qsv_decode.c
qsv_transcode.c
remux.c
resample_audio.c
scale_video.c
show_metadata.c
transcode.c
transcode_aac.c
vaapi_encode.c
vaapi_transcode.c
libavcodec
ac3_parser.h
adts_parser.h
avcodec.h	Libavcodec external API header
avdct.h
bsf.h
codec.h
codec_desc.h
codec_id.h
codec_par.h
d3d11va.h	Public libavcodec D3D11VA header
defs.h	Misc types and constants that do not belong anywhere else
dirac.h	Interface to Dirac Decoder/Encoder
dv_profile.h
dxva2.h	Public libavcodec DXVA2 header
exif.h	EXIF metadata parser
jni.h
mediacodec.h
packet.h
qsv.h
smpte_436m.h
vdpau.h	Public libavcodec VDPAU header
version.h	Libavcodec version macros
version_major.h	Libavcodec version macros
videotoolbox.h	Public libavcodec Videotoolbox header
vorbis_parser.h	A public API for Vorbis parsing
libavdevice
avdevice.h	Main libavdevice API header
version.h	Libavdevice version macros
version_major.h	Libavdevice version macros
libavfilter
avfilter.h	Main libavfilter public API header
buffersink.h	Memory buffer sink API for audio and video
buffersrc.h	Memory buffer source API
version.h	Libavfilter version macros
version_major.h	Libavfilter version macros
libavformat
avformat.h	Main libavformat public API header
avio.h	Buffered I/O operations
version.h	Libavformat version macros
version_major.h	Libavformat version macros
libavutil
adler32.h	Public header for Adler-32 hash function implementation
aes.h
aes_ctr.h
ambient_viewing_environment.h
attributes.h	Macro definitions for various function/variable attributes
audio_fifo.h	Audio FIFO Buffer
avassert.h	Simple assert() macros that are a bit more flexible than ISO C assert()
avstring.h
avutil.h	Convenience header that includes libavutil's core
base64.h
blowfish.h
bprint.h	AVBPrint public header
bswap.h	Byte swapping routines
buffer.h	Refcounted data buffer API
camellia.h	Public header for libavutil CAMELLIA algorithm
cast5.h	Public header for libavutil CAST5 algorithm
channel_layout.h	Public libavutil channel layout APIs header
common.h	Common internal and external API header
container_fifo.h
cpu.h
crc.h	Public header for CRC hash function implementation
csp.h	Colorspace value utility functions for libavutil
des.h
detection_bbox.h
dict.h	Public dictionary API
display.h	Display matrix
dovi_meta.h	DOVI configuration
downmix_info.h	Audio downmix medatata
encryption_info.h
error.h	Error code definitions
eval.h	Simple arithmetic expression evaluator
executor.h
fifo.h	A generic FIFO API
file.h	Misc file utilities
film_grain_params.h
frame.h	Reference-counted frame API
hash.h	Generic hashing API
hdr_dynamic_metadata.h
hdr_dynamic_vivid_metadata.h
hmac.h
hwcontext.h
hwcontext_amf.h
hwcontext_cuda.h	An API-specific header for AV_HWDEVICE_TYPE_CUDA
hwcontext_d3d11va.h	An API-specific header for AV_HWDEVICE_TYPE_D3D11VA
hwcontext_d3d12va.h	An API-specific header for AV_HWDEVICE_TYPE_D3D12VA
hwcontext_drm.h	API-specific header for AV_HWDEVICE_TYPE_DRM
hwcontext_dxva2.h	An API-specific header for AV_HWDEVICE_TYPE_DXVA2
hwcontext_mediacodec.h
hwcontext_oh.h
hwcontext_opencl.h	API-specific header for AV_HWDEVICE_TYPE_OPENCL
hwcontext_qsv.h	An API-specific header for AV_HWDEVICE_TYPE_QSV
hwcontext_vaapi.h	API-specific header for AV_HWDEVICE_TYPE_VAAPI
hwcontext_vdpau.h	An API-specific header for AV_HWDEVICE_TYPE_VDPAU
hwcontext_videotoolbox.h	An API-specific header for AV_HWDEVICE_TYPE_VIDEOTOOLBOX
hwcontext_vulkan.h	API-specific header for AV_HWDEVICE_TYPE_VULKAN
iamf.h	Immersive Audio Model and Formats API header
imgutils.h	Misc image utilities
intfloat.h
intreadwrite.h
lfg.h
log.h
lzo.h
macros.h	Utility Preprocessor macros
mastering_display_metadata.h
mathematics.h
md5.h	Public header for MD5 hash function implementation
mem.h	Memory handling functions
motion_vector.h
murmur3.h	Public header for MurmurHash3 hash function implementation
opt.h	AVOptions
parseutils.h	Misc parsing utilities
pixdesc.h
pixelutils.h
pixfmt.h	Pixel format definitions
random_seed.h
rational.h	Utilities for rational number calculation
rc4.h
refstruct.h
replaygain.h
ripemd.h	Public header for RIPEMD hash function implementation
samplefmt.h
sha.h	Public header for SHA-1 & SHA-256 hash function implementations
sha512.h	Public header for SHA-512 implementation
spherical.h	Spherical video
stereo3d.h	Stereoscopic video
tdrdi.h	Spherical video
tea.h	Public header for libavutil TEA algorithm
threadmessage.h
time.h
timecode.h	Timecode helpers header
timestamp.h	Timestamp utils, mostly useful for debugging/logging purposes
tree.h	A tree container
twofish.h	Public header for libavutil TWOFISH algorithm
tx.h
uuid.h	UUID parsing and serialization utilities
version.h	Libavutil version macros
video_enc_params.h
video_hint.h
xtea.h	Public header for libavutil XTEA algorithm
libswresample
swresample.h	Libswresample public header
version.h	Libswresample version macros
version_major.h	Libswresample version macros
libswscale
swscale.h	External API header
version.h	Swscale version macros
version_major.h	Swscale version macros