ffmpeg: add support of specifying Android ABI version when building FFmpeg

Also add proper error message when using NDK that doesn't support requested ABI version.

Author: equeim

libraries/decoder_ffmpeg/README.md

@@ -29,7 +29,7 @@ FFMPEG_MODULE_PATH="$(pwd)/libraries/decoder_ffmpeg/src/main"
 ```
 
 * Download the [Android NDK][] and set its location in a shell variable.
-  This build configuration has been tested on NDK r21.
+  This build configuration has been tested on NDK r26b (r23c if ANDROID_ABI is 16).
 
 ```
 NDK_PATH="<path to Android NDK>"
@@ -41,6 +41,12 @@ NDK_PATH="<path to Android NDK>"
 HOST_PLATFORM="linux-x86_64"
 ```
 
+* Set the ABI version for native code (typically it's equal to minSdk and must not exceed it):
+
+```
+ANDROID_ABI=16
+```
+
 *   Fetch FFmpeg and checkout an appropriate branch. We cannot guarantee
     compatibility with all versions of FFmpeg. We currently recommend version
     6.0:
@@ -74,7 +80,7 @@ ln -s "$FFMPEG_PATH" ffmpeg
 ```
 cd "${FFMPEG_MODULE_PATH}/jni" && \
 ./build_ffmpeg.sh \
-  "${FFMPEG_MODULE_PATH}" "${NDK_PATH}" "${HOST_PLATFORM}" "${ENABLED_DECODERS[@]}"
+  "${FFMPEG_MODULE_PATH}" "${NDK_PATH}" "${HOST_PLATFORM}" "${ANDROID_ABI}" "${ENABLED_DECODERS[@]}"
 ```
 
 ## Build instructions (Windows)

libraries/decoder_ffmpeg/src/main/jni/build_ffmpeg.sh

@@ -16,11 +16,17 @@
 #
 set -eu
 
-FFMPEG_MODULE_PATH=$1
-NDK_PATH=$2
-HOST_PLATFORM=$3
-ENABLED_DECODERS=("${@:4}")
-JOBS=$(nproc 2> /dev/null || sysctl -n hw.ncpu 2> /dev/null || echo 4)
+FFMPEG_MODULE_PATH="$1"
+echo "FFMPEG_MODULE_PATH is ${FFMPEG_MODULE_PATH}"
+NDK_PATH="$2"
+echo "NDK path is ${NDK_PATH}"
+HOST_PLATFORM="$3"
+echo "Host platform is ${HOST_PLATFORM}"
+ANDROID_ABI="$4"
+echo "ANDROID_ABI is ${ANDROID_ABI}"
+ENABLED_DECODERS=("${@:5}")
+echo "Enabled decoders are ${ENABLED_DECODERS[@]}"
+JOBS="$(nproc 2> /dev/null || sysctl -n hw.ncpu 2> /dev/null || echo 4)"
 echo "Using $JOBS jobs for make"
 COMMON_OPTIONS="
     --target-os=android
@@ -45,12 +51,28 @@ for decoder in "${ENABLED_DECODERS[@]}"
 do
     COMMON_OPTIONS="${COMMON_OPTIONS} --enable-decoder=${decoder}"
 done
+
+ARMV7_CLANG="${TOOLCHAIN_PREFIX}/armv7a-linux-androideabi${ANDROID_ABI}-clang"
+if [[ -e "${TOOLCHAIN_PREFIX}" && ! -e "$ARMV7_CLANG" ]]
+then
+    echo "AVMv7 Clang compiler with path $ARMV7_CLANG does not exist"
+    echo "It's likely your NDK version doesn't support ANDROID_ABI $ANDROID_ABI"
+    echo "Either use older version of NDK or raise ANDROID_ABI (be aware that ANDROID_ABI must not be greater than your application's minSdk)"
+    exit 1
+fi
+ANDROID_ABI_64BIT="$ANDROID_ABI"
+if [[ "$ANDROID_ABI_64BIT" -lt 21 ]]
+then
+    echo "Using ANDROID_ABI 21 for 64-bit architectures"
+    ANDROID_ABI_64BIT=21
+fi
+
 cd "${FFMPEG_MODULE_PATH}/jni/ffmpeg"
 ./configure \
     --libdir=android-libs/armeabi-v7a \
     --arch=arm \
     --cpu=armv7-a \
-    --cross-prefix="${TOOLCHAIN_PREFIX}/armv7a-linux-androideabi16-" \
+    --cross-prefix="${TOOLCHAIN_PREFIX}/armv7a-linux-androideabi${ANDROID_ABI}-" \
     --nm="${TOOLCHAIN_PREFIX}/llvm-nm" \
     --ar="${TOOLCHAIN_PREFIX}/llvm-ar" \
     --ranlib="${TOOLCHAIN_PREFIX}/llvm-ranlib" \
@@ -65,7 +87,7 @@ make clean
     --libdir=android-libs/arm64-v8a \
     --arch=aarch64 \
     --cpu=armv8-a \
-    --cross-prefix="${TOOLCHAIN_PREFIX}/aarch64-linux-android21-" \
+    --cross-prefix="${TOOLCHAIN_PREFIX}/aarch64-linux-android${ANDROID_ABI_64BIT}-" \
     --nm="${TOOLCHAIN_PREFIX}/llvm-nm" \
     --ar="${TOOLCHAIN_PREFIX}/llvm-ar" \
     --ranlib="${TOOLCHAIN_PREFIX}/llvm-ranlib" \
@@ -78,7 +100,7 @@ make clean
     --libdir=android-libs/x86 \
     --arch=x86 \
     --cpu=i686 \
-    --cross-prefix="${TOOLCHAIN_PREFIX}/i686-linux-android16-" \
+    --cross-prefix="${TOOLCHAIN_PREFIX}/i686-linux-android${ANDROID_ABI}-" \
     --nm="${TOOLCHAIN_PREFIX}/llvm-nm" \
     --ar="${TOOLCHAIN_PREFIX}/llvm-ar" \
     --ranlib="${TOOLCHAIN_PREFIX}/llvm-ranlib" \
@@ -92,7 +114,7 @@ make clean
     --libdir=android-libs/x86_64 \
     --arch=x86_64 \
     --cpu=x86_64 \
-    --cross-prefix="${TOOLCHAIN_PREFIX}/x86_64-linux-android21-" \
+    --cross-prefix="${TOOLCHAIN_PREFIX}/x86_64-linux-android${ANDROID_ABI_64BIT}-" \
     --nm="${TOOLCHAIN_PREFIX}/llvm-nm" \
     --ar="${TOOLCHAIN_PREFIX}/llvm-ar" \
     --ranlib="${TOOLCHAIN_PREFIX}/llvm-ranlib" \