ffmpeg.cmake

# SPDX-License-Identifier: BSD-3-Clause
#
# Cross-build decoder-only FFmpeg static libraries for the ffmpeg_dec module.
#
# Invokes FFmpeg's autotools build as an ExternalProject, cross-compiled with the
# Zephyr target toolchain, enabling only the decoders selected in Kconfig. The
# source comes from the west-pinned FFmpeg project (see west.yml). Produces
# libavcodec/libavutil/libswresample .a under ${FFMPEG_INSTALL_DIR} for the LLEXT
# to link, and defines the 'ffmpeg_ext' target it must depend on.

include(ExternalProject)

# --- 1. Locate the FFmpeg source (west module), overridable for local trees ---
if(NOT DEFINED SOF_FFMPEG_SRC_DIR)
	set(SOF_FFMPEG_SRC_DIR "${sof_top_dir}/../modules/audio/ffmpeg"
	    CACHE PATH "FFmpeg source tree (west-pinned)")
endif()
cmake_path(NORMAL_PATH SOF_FFMPEG_SRC_DIR)
if(NOT EXISTS "${SOF_FFMPEG_SRC_DIR}/configure")
	message(FATAL_ERROR
		"ffmpeg_dec: FFmpeg source not found at '${SOF_FFMPEG_SRC_DIR}'.\n"
		"Run 'west update' (FFmpeg is pinned in west.yml) or pass "
		"-DSOF_FFMPEG_SRC_DIR=<path-to-clean-ffmpeg-checkout>.")
endif()

# --- 2. Kconfig -> --enable-decoder / --enable-parser lists ---
set(_ff_decoders "")
set(_ff_parsers "")
if(CONFIG_FFMPEG_DEC_FLAC)
	list(APPEND _ff_decoders flac)
	list(APPEND _ff_parsers  flac)
endif()
if(CONFIG_FFMPEG_DEC_AAC)
	list(APPEND _ff_decoders aac aac_latm)
	list(APPEND _ff_parsers  aac aac_latm)
endif()
if(CONFIG_FFMPEG_DEC_OPUS)
	list(APPEND _ff_decoders opus)
	list(APPEND _ff_parsers  opus)
endif()
if(CONFIG_FFMPEG_DEC_MP3)
	list(APPEND _ff_decoders mp3)
	list(APPEND _ff_parsers  mpegaudio)
endif()
if(NOT _ff_decoders)
	message(FATAL_ERROR "ffmpeg_dec: no decoder selected (Kconfig FFMPEG_DEC_*)")
endif()
list(JOIN _ff_decoders "," _ff_dec_csv)
list(JOIN _ff_parsers  "," _ff_par_csv)

# --- 2b. Kconfig -> libavfilter audio filters (off unless a filter is chosen) ---
set(_ff_avfilter_cfg --disable-avfilter)
if(CONFIG_FFMPEG_BUILD_AVFILTER)
	set(_ff_filters "")
	if(CONFIG_FFMPEG_FILTER_AFFTDN)
		list(APPEND _ff_filters afftdn)
	endif()
	list(JOIN _ff_filters "," _ff_filt_csv)
	# abuffer/abuffersink feed/drain a filter graph; aformat negotiates format.
	set(_ff_avfilter_cfg
		--enable-avfilter
		--enable-filter=abuffer,abuffersink,aformat,${_ff_filt_csv})
	message(STATUS "ffmpeg_dec: enabling avfilter, filters [${_ff_filt_csv}]")
endif()

# --- 3. Derive the cross toolchain prefix from the Zephyr target compiler ---
# e.g. .../bin/xtensa-intel_ace30_ptl_zephyr-elf-gcc
#   -> prefix .../bin/xtensa-intel_ace30_ptl_zephyr-elf-
get_filename_component(_tc_dir  "${CMAKE_C_COMPILER}" DIRECTORY)
get_filename_component(_tc_name "${CMAKE_C_COMPILER}" NAME)
string(REGEX REPLACE "gcc$" "" _tc_prefix_name "${_tc_name}")
set(_ff_cross_prefix "${_tc_dir}/${_tc_prefix_name}")

# GCC 14 (Zephyr SDK) promotes these to errors; FFmpeg 7.x trips them.
set(_ff_extra_cflags "-fPIC -Wno-error=incompatible-pointer-types -Wno-error=implicit-function-declaration")

set(FFMPEG_INSTALL_DIR "${CMAKE_CURRENT_BINARY_DIR}/ffmpeg-install" CACHE INTERNAL "ffmpeg_dec libs")

# Hot/cold split: GCC emits av_cold (init/setup) functions into .text.unlikely.
# We rename that to SOF's .cold (post-install, below) so the LLEXT loader places
# it in DRAM. -mtext-section-literals interleaves each function's Xtensa L32R
# literals into its text section (as SOF does for LLEXT module code) so the
# renamed section carries its literals and L32R stays in range. We deliberately
# do NOT use -ffunction-sections: keeping one .text.unlikely per object lets a
# single objcopy --rename-section catch it, and lets .cold be placed by SOF's
# existing orphan .cold handling (a hand-written linker script that forces .cold
# ahead of .text overruns the SRAM budget and overlaps .rodata for big codecs).
if(CONFIG_FFMPEG_DEC_COLD_SPLIT)
	# -mlongcalls: cold code lives in DRAM (.cold, relocated by the loader) far
	# from the hot SRAM .text, so calls between them exceed call8 range; longcalls
	# emit an indirect L32R+CALLX with unlimited range. -mtext-section-literals
	# keeps each function's literals in its own text section so the rename carries
	# them. Coarse split: rename the whole FFmpeg .text (not just av_cold) into
	# .cold so essentially all of libav* executes from DRAM, freeing SRAM.
	set(_ff_extra_cflags "${_ff_extra_cflags} -mtext-section-literals -mlongcalls")
	set(_ff_objcopy "${_ff_cross_prefix}objcopy")
	set(_ff_cold_rename
		COMMAND ${_ff_objcopy} --rename-section .text=.cold
			${FFMPEG_INSTALL_DIR}/lib/libavcodec.a
		COMMAND ${_ff_objcopy} --rename-section .text=.cold
			${FFMPEG_INSTALL_DIR}/lib/libavutil.a
		COMMAND ${_ff_objcopy} --rename-section .text=.cold
			${FFMPEG_INSTALL_DIR}/lib/libswresample.a)
endif()

# --- 3b. MP3 encoder via libshine (fixed-point; FFmpeg has no native one) ---
set(_ff_cfg_env "PATH=${_tc_dir}:$ENV{PATH}")
set(_ff_shine_cfg "")
set(_ff_shine_dep "")
if(CONFIG_FFMPEG_ENC_MP3)
	set(SHINE_SRC "${sof_top_dir}/../modules/audio/shine")
	if(NOT EXISTS "${SHINE_SRC}/src/lib/layer3.h")
		message(FATAL_ERROR "ffmpeg_dec: libshine source not at '${SHINE_SRC}'; run 'west update'")
	endif()
	set(SHINE_INSTALL "${CMAKE_CURRENT_BINARY_DIR}/shine-install")
	file(MAKE_DIRECTORY "${SHINE_INSTALL}/lib/pkgconfig" "${SHINE_INSTALL}/include/shine")
	# pkg-config file for FFmpeg's require_pkg_config libshine.
	file(WRITE "${SHINE_INSTALL}/lib/pkgconfig/shine.pc"
"prefix=${SHINE_INSTALL}
libdir=\${prefix}/lib
includedir=\${prefix}/include
Name: shine
Description: Shine fixed-point MP3 encoder
Version: 3.1.1
Libs: -L\${libdir} -lshine
Cflags: -I\${includedir}
")
	# FFmpeg's -lshine link *test* pulls newlib malloc -> Zephyr runtime syms
	# (z_errno_wrap, ...) that only exist at module load. Provide dummies so the
	# configure test links; --extra-ldflags only affects tests, not the .a build.
	file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/shine_cfgstub.c"
"int z_errno_wrap(void){return 0;}
void *stdout;
int open(const char *p, int f, ...){return -1;}
void *sbrk(int i){return (void *)-1;}
")
	# libshine's lib needs no config.h; build the objects directly and archive
	# (its autotools CLI/shared link cannot work bare-metal).
	file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/shine-build.sh"
"#!/bin/sh
set -e
export PATH=${_tc_dir}:\$PATH
mkdir -p ${CMAKE_CURRENT_BINARY_DIR}/shine-obj
for f in ${SHINE_SRC}/src/lib/*.c; do
	${CMAKE_C_COMPILER} -O2 -fPIC -mtext-section-literals -DSHINE_HAVE_BSWAP_H \\
		-I${SHINE_SRC}/src/lib -c \"\$f\" \\
		-o ${CMAKE_CURRENT_BINARY_DIR}/shine-obj/\$(basename \"\$f\").o
done
${_ff_cross_prefix}ar rcs ${SHINE_INSTALL}/lib/libshine.a ${CMAKE_CURRENT_BINARY_DIR}/shine-obj/*.o
cp ${SHINE_SRC}/src/lib/layer3.h ${SHINE_INSTALL}/include/shine/layer3.h
${CMAKE_C_COMPILER} -fPIC -c ${CMAKE_CURRENT_BINARY_DIR}/shine_cfgstub.c \\
	-o ${CMAKE_CURRENT_BINARY_DIR}/shine_cfgstub.o
")
	add_custom_command(
		OUTPUT "${SHINE_INSTALL}/lib/libshine.a" "${CMAKE_CURRENT_BINARY_DIR}/shine_cfgstub.o"
		COMMAND sh "${CMAKE_CURRENT_BINARY_DIR}/shine-build.sh"
		VERBATIM)
	add_custom_target(shine_ext DEPENDS "${SHINE_INSTALL}/lib/libshine.a")

	set(_ff_cfg_env "PATH=${_tc_dir}:$ENV{PATH}" "PKG_CONFIG_PATH=${SHINE_INSTALL}/lib/pkgconfig")
	set(_ff_shine_cfg --enable-libshine --enable-encoder=libshine --pkg-config=pkg-config
		"--extra-ldflags=${CMAKE_CURRENT_BINARY_DIR}/shine_cfgstub.o")
	set(_ff_shine_dep shine_ext)
	message(STATUS "ffmpeg_dec: enabling MP3 encoder via libshine (${SHINE_SRC})")
endif()

# --- 4. Configure + make + install (out-of-tree; source must be clean) ---
ExternalProject_Add(ffmpeg_ext
	DEPENDS ${_ff_shine_dep}
	SOURCE_DIR      "${SOF_FFMPEG_SRC_DIR}"
	BUILD_IN_SOURCE 0
	CONFIGURE_COMMAND
		${CMAKE_COMMAND} -E env ${_ff_cfg_env}
		<SOURCE_DIR>/configure
			--prefix=${FFMPEG_INSTALL_DIR}
			--enable-cross-compile --target-os=none --arch=xtensa
			--cross-prefix=${_ff_cross_prefix} --cc=${CMAKE_C_COMPILER}
			--disable-asm --disable-all --disable-everything --disable-autodetect
			--disable-programs --disable-doc --disable-network
			--disable-avformat --disable-avdevice ${_ff_avfilter_cfg}
			--disable-swscale --disable-postproc
			--disable-pthreads --disable-w32threads --disable-os2threads
			--disable-runtime-cpudetect --disable-debug
			--enable-avcodec --enable-avutil --enable-swresample
			--enable-decoder=${_ff_dec_csv} --enable-parser=${_ff_par_csv}
			${_ff_shine_cfg}
			--enable-small --enable-pic
			"--extra-cflags=${_ff_extra_cflags}"
	BUILD_COMMAND
		${CMAKE_COMMAND} -E env "PATH=${_tc_dir}:$ENV{PATH}" make -j 8
	INSTALL_COMMAND make install
		${_ff_cold_rename}
	BUILD_BYPRODUCTS
		${FFMPEG_INSTALL_DIR}/lib/libavcodec.a
		${FFMPEG_INSTALL_DIR}/lib/libavutil.a
		${FFMPEG_INSTALL_DIR}/lib/libswresample.a
)

message(STATUS "ffmpeg_dec: cross-building FFmpeg decoders [${_ff_dec_csv}] from ${SOF_FFMPEG_SRC_DIR}")