Raise initial memory from 1 GB to 2 GB

wasm/build-scripts/build-ffmpeg.sh

@@ -21,7 +21,7 @@ FLAGS=(
   -s EXPORT_NAME="createFFmpegCore"             # assign export name for browser
   -s EXPORTED_FUNCTIONS="[_main, _proxy_main]"  # export main and proxy_main funcs
   -s EXTRA_EXPORTED_RUNTIME_METHODS="[FS, cwrap, ccall, setValue, writeAsciiToMemory]"   # export preamble funcs
-  -s INITIAL_MEMORY=1073741824                  # 1073741824 bytes = 1 GB
+  -s INITIAL_MEMORY=2146435072                  # 64 KB * 1024 * 16 * 2047 = 2146435072 bytes ~= 2 GB
   $OPTIM_FLAGS
 )
 echo "FFMPEG_EM_FLAGS=${FLAGS[@]}"