Find ffmpeg.exe anywhere in .minecraft folder (closes #347)

Thanks to Lucky56 for testing!

docs/content.md

@@ -22,14 +22,17 @@ To render your creations with **Replay Mod** you will need to have FFmpeg instal
 ### Windows [windows]
 Download the **latest** FFmpeg build from <http://ffmpeg.zeranoe.com/builds/>.
 
-In your `.minecraft` folder, create a `ffmpeg` folder. Extract the downloaded .zip file into this folder. The FFmpeg executable should end up at `.minecraft\ffmpeg\bin\ffmpeg.exe`.
+Extract the downloaded .zip file into your `.minecraft` folder.
+
+Historically the exact location inside the `.minecraft` folder was important, this is no longer the case.
+It is sufficient for the `ffmpeg.exe` to be anywhere inside your `.minecraft` folder.
 
 **Notes for alternative launchers**
 - Twitch launcher by default installs Minecraft instances in C:\\Users\\*username*\\Twitch\\Minecraft\\Instances\\*instancename*\\
 - GD Launcher by default installs Minecraft instances in C:\\Users\\*username*\\AppData\\Roaming\\gdlauncher_next\\instances\\*instancename*\\
 - MultiMC by default installs Minecraft instances in C:\\Program Files (x86)\\MultiMC\\instances\\*Instancename*\\.minecraft\\
 
-For these launchers, make sure FFmpeg exists in `instancename\ffmpeg\bin\ffmpeg.exe` (Twitch / GD) or `Instancename\.minecraft\ffmpeg\bin\ffmpeg.exe` (MultiMC)
+For these launchers, make sure FFmpeg exists inside the corresponding folder.
 
 ### Mac OSX [mac]
 On OSX, you can install **FFmpeg** with **[Homebrew](http://brew.sh/)** using `brew install ffmpeg`.

src/main/java/com/replaymod/render/RenderSettings.java

@@ -7,6 +7,12 @@ import net.minecraft.client.resource.language.I18n;
 import net.minecraft.util.Util;
 
 import java.io.File;
+import java.io.IOException;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.Optional;
@@ -253,11 +259,35 @@ public class RenderSettings {
         switch (Util.getOperatingSystem()) {
             case WINDOWS:
                 // Allow windows users to unpack the ffmpeg archive into a sub-folder of their .minecraft folder
-                File inDotMinecraft = new File(MCVer.getMinecraft().runDirectory, "ffmpeg/bin/ffmpeg.exe");
+                File dotMinecraft = MCVer.getMinecraft().runDirectory;
+                File inDotMinecraft = new File(dotMinecraft, "ffmpeg/bin/ffmpeg.exe");
                 if (inDotMinecraft.exists()) {
                     LOGGER.debug("FFmpeg found in .minecraft/ffmpeg");
                     return inDotMinecraft.getAbsolutePath();
                 }
+                // But a significant amount of people are not even able to follow instruction to do that.
+                // Instead they'll regularly put it at `.minecraft/ffmpeg-version/bin/ffmpeg.exe`
+                // or `.minecraft/ffmpeg/ffmpeg-version/bin/ffmpeg.exe`
+                // So, for support's sake, let's just search the entire .minecraft folder for an `ffmpeg.exe` file.
+                // We retain above check to have a fast path for any old installations.
+                try {
+                    Path[] result = new Path[1];
+                    Files.walkFileTree(dotMinecraft.toPath(), new SimpleFileVisitor<Path>() {
+                        @Override
+                        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
+                            if ("ffmpeg.exe".equals(file.getFileName().toString())) {
+                                result[0] = file;
+                                return FileVisitResult.TERMINATE;
+                            }
+                            return super.visitFile(file, attrs);
+                        }
+                    });
+                    if (result[0] != null) {
+                        return result[0].toAbsolutePath().toString();
+                    }
+                } catch (IOException e) {
+                    LOGGER.debug("Error searching .minecraft for ffmpeg.exe:", e);
+                }
                 break;
             case OSX:
                 // The PATH doesn't seem to be set as expected on OSX, therefore we check some common locations ourselves