Update CI/CD to use Ubuntu 24.04 and distro FFmpeg 6.x

.github/workflows/ci.yml

@@ -33,30 +33,10 @@ jobs:
           sudo apt-get install -y \
             ninja-build pkg-config nasm \
             qt6-base-dev qt6-base-dev-tools qt6-base-private-dev qt6-tools-dev qt6-tools-dev-tools \
+            libavcodec-dev libavformat-dev libavutil-dev libswscale-dev libswresample-dev \
             libopencolorio-dev libopenimageio-dev libopenexr-dev libexpat1-dev \
             portaudio19-dev libgl1-mesa-dev libxkbcommon-dev
 
-      - name: Build FFmpeg from source (Linux)
-        if: runner.os == 'Linux'
-        run: |
-          git clone --branch n8.1.1 --depth 1 https://git.ffmpeg.org/ffmpeg.git ffmpeg-src
-          cd ffmpeg-src
-          ./configure \
-            --prefix="$PWD/../ffmpeg-install" \
-            --enable-static \
-            --disable-shared \
-            --disable-doc \
-            --disable-programs \
-            --disable-avdevice \
-            --disable-network \
-            --enable-pic \
-            --enable-gpl \
-            --enable-version3
-          make -j$(nproc)
-          make install
-          cd ..
-          echo "FFMPEG_ROOT=$PWD/ffmpeg-install" >> "$GITHUB_ENV"
-
       # ------------------------------------------------------------------
       # macOS dependencies
       # ------------------------------------------------------------------
@@ -115,7 +95,6 @@ jobs:
             -DBUILD_TESTS=ON \
             -DBUILD_QT6=ON \
             -DOCIO_LOCATION=/usr \
-            -DFFMPEG_ROOT="${FFMPEG_ROOT}" \
             -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
 
       - name: Configure (macOS)