Re-enable FFmpeg x86-64 assembly on manylinux (#2089)

* Re-enable FFmpeg x86 assembly on manylinux

* Clarify x86-64 assembly scope

Author: shimat

.github/actions/build-manylinux-variant/action.yml

@@ -57,7 +57,7 @@ runs:
     - name: Install system tools (${{ inputs.variant_label }})
       shell: bash
       run: |
-        pkgs="git zip unzip pkg-config ninja-build kernel-headers perl-IPC-Cmd perl-Time-Piece"
+        pkgs="git zip unzip pkg-config ninja-build nasm yasm kernel-headers perl-IPC-Cmd perl-Time-Piece"
         if [ "${{ inputs.install_gtk3_devel }}" = "true" ]; then
           pkgs="$pkgs gtk3-devel"
         fi

packaging/docker/manylinux/README.md

@@ -4,7 +4,9 @@ The full and headless `linux-x64` packages statically link the same FFmpeg build
 
 The FFmpeg build provides OpenCV's required libraries (`avcodec`, `avformat`, `avutil`, and `swscale`), its built-in decoders, encoders, demuxers, and muxers, and non-secure local and network protocols. RTSP, TCP, UDP, HTTP, local files, and pipes are intended to work. CI exercises H.264-over-RTSP through OpenCV and checks a representative baseline of file formats and codecs in the generated feature inventory.
 
-External-library autodetection is disabled. FFmpeg must not silently acquire a dependency merely because the manylinux container adds a development package. The glibc-provided iconv implementation is explicitly enabled and introduces no additional ELF dependency. Hardware acceleration, `libdrm`, `avdevice`, `avfilter`, post-processing, and `swresample` are intentionally excluded because the packaged OpenCV backend does not require them. Assembly remains disabled pending a successful position-independent static link with the current toolchain and a representative H.264 file/RTSP decode benchmark.
+External-library autodetection is disabled. FFmpeg must not silently acquire a dependency merely because the manylinux container adds a development package. The glibc-provided iconv implementation is explicitly enabled and introduces no additional ELF dependency. Hardware acceleration, `libdrm`, `avdevice`, `avfilter`, post-processing, and `swresample` are intentionally excluded because the packaged OpenCV backend does not require them.
+
+x86-64 assembly optimizations are enabled. FFmpeg's assembly objects contain direct PC-relative references to global constants that cannot be interposed when their static archives are linked into `libOpenCvSharpExtern.so`. The Linux linker therefore hides symbols from the four private FFmpeg archives with `--exclude-libs`; this resolves those references without exporting FFmpeg's private implementation from the OpenCvSharp native binding.
 
 TLS is not currently included, so HTTPS and RTSPS are outside the supported feature surface. Adding a TLS backend requires an explicit decision covering license compatibility, CA certificate discovery, binary size, transitive dependencies, manylinux portability, and regression tests.
 

packaging/docker/manylinux/build_static_deps.sh

@@ -54,7 +54,6 @@ CONFIGURE_FLAGS=(
     --enable-static
     --disable-shared
     --enable-pic
-    --disable-asm
     --disable-autodetect
     --disable-doc
     --disable-programs
@@ -89,6 +88,13 @@ mkdir -p "${INVENTORY_DIR}"
     echo "[configure-flags]"
     printf '%s\n' "${CONFIGURE_FLAGS[@]}"
 
+    echo
+    echo "[assembly]"
+    for option in inline_asm x86asm; do
+        value=$(awk -v macro="HAVE_${option^^}" '$1 == "#define" && $2 == macro { print $3 }' config.h)
+        echo "${option}=${value:-0}"
+    done
+
     for component in protocol demuxer muxer decoder encoder; do
         echo
         echo "[${component}s]"

packaging/docker/manylinux/verify_ffmpeg_features.sh

@@ -65,6 +65,12 @@ if ! grep -qx -- '--disable-autodetect' "${INVENTORY_PATH}"; then
     exit 1
 fi
 
+if grep -qx -- '--disable-asm' "${INVENTORY_PATH}" ||
+   ! grep -qx -- 'x86asm=1' "${INVENTORY_PATH}"; then
+    echo "ERROR: FFmpeg x86-64 assembly optimizations are disabled"
+    exit 1
+fi
+
 if grep -Eq '^(gnutls|libtls|mbedtls|openssl|schannel|securetransport)=1$' "${INVENTORY_PATH}"; then
     echo "ERROR: an unapproved TLS backend was enabled"
     grep -E '^(gnutls|libtls|mbedtls|openssl|schannel|securetransport)=' "${INVENTORY_PATH}"

src/OpenCvSharpExtern/CMakeLists.txt

@@ -64,6 +64,14 @@ if(OpenCV_FOUND)
 			# 3rd-party dependency (e.g. libatomic.so.1) but whose symbols are never actually
 			# referenced by the resulting binary. See issue #2065.
 			target_link_options(OpenCvSharpExtern PRIVATE -Wl,--as-needed)
+
+			# FFmpeg's optimized x86-64 assembly uses direct PC-relative references to global
+			# constants. Keep the statically linked FFmpeg implementation private so those
+			# references bind locally when producing this shared library. See issue #2085.
+			foreach(ffmpeg_archive IN ITEMS libavcodec.a libavformat.a libavutil.a libswscale.a)
+				target_link_options(OpenCvSharpExtern PRIVATE
+					"-Wl,--exclude-libs,${ffmpeg_archive}")
+			endforeach()
 		endif()
 	endif()