Implement adding metadata to output video.

src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java

@@ -13,6 +13,7 @@
 import org.apache.commons.lang3.math.Fraction;
 
 import java.util.List;
+import java.util.ArrayList;
 import java.util.concurrent.TimeUnit;
 
 import static com.google.common.base.Preconditions.checkState;
@@ -56,6 +57,7 @@ public class FFmpegOutputBuilder implements Cloneable {
   public String video_preset;
   public String video_filter;
   public String video_filter_complex;
+  public List<String> video_meta_tags;
 
   public boolean subtitle_enabled = true;
 
@@ -223,6 +225,24 @@ public FFmpegOutputBuilder setComplexVideoFilter(String filter) {
     return this;
   }
 
+  /**
+   * Allows to add metadata to output video. Which keys are possible depends on the used output
+   * video codec.
+   * 
+   * @param key Metadata key, e.g. "comment"
+   * @param value Value to set for key
+   * @return This instance
+   */
+  public FFmpegOutputBuilder addMetaTag(String key, String value) {
+    this.video_enabled = true;
+    if (this.video_meta_tags == null) {
+      this.video_meta_tags = new ArrayList<>();
+    }
+
+    this.video_meta_tags.add(checkNotNull(key) + "=" + checkNotNull(value).replace("\"", ""));
+    return this;
+  }
+
   public FFmpegOutputBuilder setAudioCodec(String codec) {
     this.audio_enabled = true;
     this.audio_codec = checkNotNull(codec);
@@ -448,6 +468,12 @@ protected List<String> build(int pass) {
         args.add("-filter_complex").add(video_filter_complex);
       }
 
+      if (video_meta_tags != null) {
+        for (String meta : video_meta_tags) {
+          args.add("-metadata").add("\"" + meta + "\"");
+        }
+      }
+
     } else {
       args.add("-vn");
     }

src/test/java/net/bramp/ffmpeg/FFmpegBuilderTest.java

@@ -109,6 +109,20 @@ public void testMultipleOutputs() {
         "output1", "-s", "640x480", "output2")));
   }
 
+  /**
+   * Tests whether setting meta tags works correctly.
+   */
+  @Test
+  public void testMetaTags() {
+    FFmpegBuilder builder =
+        new FFmpegBuilder().setInput("input").addOutput("output").disableAudio().disableSubtitle()
+            .addMetaTag("comment", "My Comment").addMetaTag("title", "\"Video\"").done();
+
+    List<String> args = builder.build();
+    assertThat(args, is(Arrays.asList("-y", "-v", "error", "-i", "input", "-metadata",
+        "\"comment=My Comment\"", "-metadata", "\"title=Video\"", "-an", "-sn", "output")));
+  }
+
   @Test(expected = IllegalArgumentException.class)
   public void testNothing() {
     FFmpegBuilder builder = new FFmpegBuilder();

src/test/java/net/bramp/ffmpeg/FFmpegExecutorTest.java

@@ -62,6 +62,22 @@ public void testFilter() throws InterruptedException, ExecutionException, IOExce
     assertEquals(FFmpegJob.State.FINISHED, job.getState());
   }
 
+  @Test
+  public void testMetaTags() throws InterruptedException, ExecutionException, IOException {
+
+    FFmpegBuilder builder =
+        new FFmpegBuilder().setInput(Samples.big_buck_bunny_720p_1mb).overrideOutputFiles(true)
+            .addOutput(Samples.output_mp4).setFormat("mp4").disableAudio().setVideoCodec("mpeg4")
+            .addMetaTag("comment", "This=Nice!").addMetaTag("title", "Big Buck Bunny").done();
+
+    FFmpegExecutor executor = new FFmpegExecutor(ffmpeg, ffprobe);
+
+    FFmpegJob job = executor.createJob(builder);
+    runAndWait(job);
+
+    assertEquals(FFmpegJob.State.FINISHED, job.getState());
+  }
+
   protected void runAndWait(FFmpegJob job) throws ExecutionException, InterruptedException {
     Future<?> future = executor.submit(job);