From dcc0e0e76c53dcdcfe66b04926d65eaf4f30c45d Mon Sep 17 00:00:00 2001
From: Andrew Brampton <bramp@google.com>
Date: Sat, 18 Jun 2016 15:33:40 -0700
Subject: [PATCH 1/2] Half finished spec idea.

---
 .../ffmpeg/builder/ChapterMetadataSpec.java   |  16 +++
 .../ffmpeg/builder/FFmpegOutputBuilder.java   |   8 ++
 .../ffmpeg/builder/GlobalMetadataSpec.java    |  15 ++
 .../bramp/ffmpeg/builder/MetadataSpec.java    |  48 +++++++
 .../ffmpeg/builder/ProgramMetadataSpec.java   |  16 +++
 .../ffmpeg/builder/StreamMetadataSpec.java    |  18 +++
 .../net/bramp/ffmpeg/builder/StreamSpec.java  | 135 ++++++++++++++++++
 .../ffmpeg/builder/MetadataSpecTest.java      |  18 +++
 .../bramp/ffmpeg/builder/StreamSpecTest.java  |  28 ++++
 9 files changed, 302 insertions(+)
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/ChapterMetadataSpec.java
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/GlobalMetadataSpec.java
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/MetadataSpec.java
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/ProgramMetadataSpec.java
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/StreamMetadataSpec.java
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/StreamSpec.java
 create mode 100644 src/test/java/net/bramp/ffmpeg/builder/MetadataSpecTest.java
 create mode 100644 src/test/java/net/bramp/ffmpeg/builder/StreamSpecTest.java

diff --git a/src/main/java/net/bramp/ffmpeg/builder/ChapterMetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/ChapterMetadataSpec.java
new file mode 100644
index 00000000..1bdec202
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/ChapterMetadataSpec.java
@@ -0,0 +1,16 @@
+package net.bramp.ffmpeg.builder;
+
+public class ChapterMetadataSpec extends MetadataSpec {
+
+  public final int index;
+
+  protected ChapterMetadataSpec(int index) {
+    super(Type.Chapter);
+    this.index = index;
+  }
+
+  @Override
+  public String toString() {
+    return "c:" + index;
+  }
+}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java b/src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java
index 0fd79026..dcaa3455 100644
--- a/src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java
+++ b/src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java
@@ -309,6 +309,14 @@ public FFmpegOutputBuilder addMetaTag(String key, String value) {
     return this;
   }
 
+
+  public FFmpegOutputBuilder addMetaTag(MetadataSpec metadata_spec, String key, String value) {
+    checkNotNull(key, "Key may not be null");
+    checkNotNull(value, "Value may not be null");
+    meta_tags.add(key + "=" + value.replace("\"", ""));
+    return this;
+  }
+
   public FFmpegOutputBuilder setAudioCodec(String codec) {
     this.audio_enabled = true;
     this.audio_codec = checkNotNull(codec);
diff --git a/src/main/java/net/bramp/ffmpeg/builder/GlobalMetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/GlobalMetadataSpec.java
new file mode 100644
index 00000000..cf3153f7
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/GlobalMetadataSpec.java
@@ -0,0 +1,15 @@
+package net.bramp.ffmpeg.builder;
+
+public class GlobalMetadataSpec extends MetadataSpec {
+
+  protected final static GlobalMetadataSpec SINGLETON = new GlobalMetadataSpec();
+
+  protected GlobalMetadataSpec() {
+    super(Type.Global);
+  }
+
+  @Override
+  public String toString() {
+    return "g";
+  }
+}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/MetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/MetadataSpec.java
new file mode 100644
index 00000000..4117cf29
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/MetadataSpec.java
@@ -0,0 +1,48 @@
+package net.bramp.ffmpeg.builder;
+
+// metadata_spec can be:
+// g global (If metadata specifier is omitted, it defaults to global.)
+// s[:stream_spec]
+// c:chapter_index
+// p:program_index
+// index is meant to be zero based, by negitive is allowed as dummy values
+
+
+/**
+ * Metadata spec, as described in the "map_metadata" section of
+ * https://www.ffmpeg.org/ffmpeg-all.html#Main-options
+ */
+public abstract class MetadataSpec {
+
+  enum Type {
+    Global, Stream, Chapter, Program
+  }
+
+  public final Type type;
+
+  protected MetadataSpec(Type type) {
+    this.type = type;
+  }
+
+  public abstract String toString();
+
+  public static GlobalMetadataSpec global() {
+    return GlobalMetadataSpec.SINGLETON;
+  }
+
+  public static ChapterMetadataSpec chapter(int index) {
+    return new ChapterMetadataSpec(index);
+  }
+
+  public static ProgramMetadataSpec program(int index) {
+    return new ProgramMetadataSpec(index);
+  }
+
+  public static StreamMetadataSpec stream(StreamSpec spec) {
+    return new StreamMetadataSpec(spec);
+  }
+
+  public static StreamMetadataSpec stream(int spec) {
+    return new StreamMetadataSpec(spec);
+  }
+}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/ProgramMetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/ProgramMetadataSpec.java
new file mode 100644
index 00000000..46d3c362
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/ProgramMetadataSpec.java
@@ -0,0 +1,16 @@
+package net.bramp.ffmpeg.builder;
+
+public class ProgramMetadataSpec extends MetadataSpec {
+
+  public final int index;
+
+  protected ProgramMetadataSpec(int index) {
+    super(Type.Program);
+    this.index = index;
+  }
+
+  @Override
+  public String toString() {
+    return "p:" + index;
+  }
+}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/StreamMetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/StreamMetadataSpec.java
new file mode 100644
index 00000000..24d37029
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/StreamMetadataSpec.java
@@ -0,0 +1,18 @@
+package net.bramp.ffmpeg.builder;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+public class StreamMetadataSpec extends MetadataSpec {
+
+  public final StreamSpec spec;
+
+  protected StreamMetadataSpec(StreamSpec spec) {
+    super(Type.Stream);
+    this.spec = checkNotNull(spec);
+  }
+
+  @Override
+  public String toString() {
+    return "s:" + spec.toString();
+  }
+}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/StreamSpec.java b/src/main/java/net/bramp/ffmpeg/builder/StreamSpec.java
new file mode 100644
index 00000000..1300f41f
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/StreamSpec.java
@@ -0,0 +1,135 @@
+package net.bramp.ffmpeg.builder;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * https://ffmpeg.org/ffmpeg.html#Stream-specifiers
+ */
+public abstract class StreamSpec {
+
+  enum Type {
+    StreamIndex, Program, StreamId, Metadata, Usable
+  }
+
+  enum StreamType {
+    Any(""),
+    Video("v"),
+    PureVideo("V"),
+    Audio("a"),
+    Subtiles("s"),
+    Data("d"),
+    Attachments("t");
+
+    final String prefix;
+
+    StreamType(String prefix) {
+      this.prefix = prefix;
+    }
+
+    public String toString() {
+      return prefix;
+    }
+  }
+
+  public final Type type;
+
+  protected StreamSpec(Type type) {
+    this.type = type;
+  }
+
+  public static class IndexStreamSpec extends StreamSpec {
+
+  }
+
+  public static class ProgramStreamSpec extends StreamSpec {
+
+  }
+
+  public static class IdStreamSpec extends StreamSpec {
+
+  }
+
+  public static class MetadataStreamSpec extends StreamSpec {
+
+    public final String key, value;
+
+    protected MetadataStreamSpec(String key, String value) {
+      super(Type.Metadata);
+      this.key = checkNotNull(key);
+      this.value = value;
+    }
+
+    @Override
+    public String toString() {
+      return "m:" + key + (value != null ? ":" + value : "");
+    }
+  }
+
+  public static class UsableStreamSpec extends StreamSpec {
+    protected final static UsableStreamSpec SINGLETON = new UsableStreamSpec();
+
+    protected UsableStreamSpec() {
+      super(Type.Usable);
+    }
+
+    @Override
+    public String toString() {
+      return "u";
+    }
+  }
+
+  public abstract String toString();
+
+  public StreamSpec stream(int stream_index) {
+    return null;
+  }
+
+  public StreamSpec stream(StreamType stream_type) {
+    checkNotNull(stream_type);
+    return null;
+  }
+
+  public StreamSpec stream(StreamType stream_type, int stream_index) {
+    checkNotNull(stream_type);
+    return null;
+  }
+
+  public StreamSpec program(int program_id) {
+    return null;
+  }
+
+  public StreamSpec program(int program_id, int stream_index) {
+    return null;
+  }
+
+  public StreamSpec id(int stream_id) {
+    return null;
+  }
+
+  public StreamSpec tag(String key) {
+    checkNotNull(key);
+    return null;
+  }
+
+  public StreamSpec tag(String key, String value) {
+    checkNotNull(key);
+    checkNotNull(value);
+    return null;
+  }
+
+  public StreamSpec usable() {
+    return UsableStreamSpec.SINGLETON;
+  }
+}
+
+
+// metadata_spec can be:
+// g global (If metadata specifier is omitted, it defaults to global.)
+// s[:stream_spec]
+// c:chapter_index
+// p:program_index
+// index is meant to be zero based, by negitive is allowed as dummy values
+/*
+ * public abstract class MetadataSpec { global() stream(index(0)) stream(video(), index(0))
+ * chapter(1) program(1) }
+ */
diff --git a/src/test/java/net/bramp/ffmpeg/builder/MetadataSpecTest.java b/src/test/java/net/bramp/ffmpeg/builder/MetadataSpecTest.java
new file mode 100644
index 00000000..5403fa58
--- /dev/null
+++ b/src/test/java/net/bramp/ffmpeg/builder/MetadataSpecTest.java
@@ -0,0 +1,18 @@
+package net.bramp.ffmpeg.builder;
+
+import org.junit.Test;
+
+import static net.bramp.ffmpeg.builder.MetadataSpec.*;
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.*;
+
+public class MetadataSpecTest {
+
+  @Test
+  public void testMetaSpec() {
+    assertThat(global().toString(), is("g"));
+    assertThat(chapter(1).toString(), is("c:1"));
+    assertThat(program(1).toString(), is("p:1"));
+    assertThat(stream(1).toString(), is("s:1"));
+  }
+}
diff --git a/src/test/java/net/bramp/ffmpeg/builder/StreamSpecTest.java b/src/test/java/net/bramp/ffmpeg/builder/StreamSpecTest.java
new file mode 100644
index 00000000..c93328e7
--- /dev/null
+++ b/src/test/java/net/bramp/ffmpeg/builder/StreamSpecTest.java
@@ -0,0 +1,28 @@
+package net.bramp.ffmpeg.builder;
+
+import static net.bramp.ffmpeg.builder.MetadataSpec.stream;
+import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.*;
+
+public class StreamSpecTest {
+
+  @Test
+  public void testStreamSpec() {
+    assertThat(stream(1).toString(), is("1"));
+    assertThat(stream(VIDEO, 1).toString(), is("v:1"));
+
+    assertThat(chapter(1).toString(), is("c:1"));
+    assertThat(program(1).toString(), is("p:1"));
+  }
+
+  addMetaTag("key", "value", );
+  addMetaTag("key", "value", chapter(1));
+  addMetaTag("key", "value", program(1));
+  addMetaTag("key", "value", stream(0));
+  addMetaTag("key", "value", stream(VIDEO, 0);
+  addMetaTag("key", "value", stream(AUDIO, 0);
+  addMetaTag("key", "value", stream(id(0x502));
+  addMetaTag("key", "value", stream(tag("key2", "value2"))); // This one is confusing, key2 refers to the output stream, and would apply key/value to any output stream already with key2/value2.
+  */
+}
+}

From 8c2f4ab59fcf2b37a124e341bcd46f9e5206dc0d Mon Sep 17 00:00:00 2001
From: Andrew Brampton <bramp@google.com>
Date: Sat, 18 Jun 2016 20:12:30 -0700
Subject: [PATCH 2/2] Add support for metadata_specifier. Fixes #25

---
 .../ffmpeg/builder/ChapterMetadataSpec.java   |  16 ---
 .../ffmpeg/builder/FFmpegOutputBuilder.java   |  52 +++++--
 .../ffmpeg/builder/GlobalMetadataSpec.java    |  15 --
 .../bramp/ffmpeg/builder/MetadataSpec.java    |  48 -------
 .../ffmpeg/builder/MetadataSpecifier.java     |  76 ++++++++++
 .../ffmpeg/builder/ProgramMetadataSpec.java   |  16 ---
 .../ffmpeg/builder/StreamMetadataSpec.java    |  18 ---
 .../net/bramp/ffmpeg/builder/StreamSpec.java  | 135 ------------------
 .../bramp/ffmpeg/builder/StreamSpecifier.java | 118 +++++++++++++++
 .../ffmpeg/builder/StreamSpecifierType.java   |  43 ++++++
 .../ffmpeg/builder/FFmpegBuilderTest.java     |  43 +++++-
 .../ffmpeg/builder/MetadataSpecTest.java      |  12 +-
 .../bramp/ffmpeg/builder/StreamSpecTest.java  |  37 ++---
 13 files changed, 346 insertions(+), 283 deletions(-)
 delete mode 100644 src/main/java/net/bramp/ffmpeg/builder/ChapterMetadataSpec.java
 delete mode 100644 src/main/java/net/bramp/ffmpeg/builder/GlobalMetadataSpec.java
 delete mode 100644 src/main/java/net/bramp/ffmpeg/builder/MetadataSpec.java
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/MetadataSpecifier.java
 delete mode 100644 src/main/java/net/bramp/ffmpeg/builder/ProgramMetadataSpec.java
 delete mode 100644 src/main/java/net/bramp/ffmpeg/builder/StreamMetadataSpec.java
 delete mode 100644 src/main/java/net/bramp/ffmpeg/builder/StreamSpec.java
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/StreamSpecifier.java
 create mode 100644 src/main/java/net/bramp/ffmpeg/builder/StreamSpecifierType.java

diff --git a/src/main/java/net/bramp/ffmpeg/builder/ChapterMetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/ChapterMetadataSpec.java
deleted file mode 100644
index 1bdec202..00000000
--- a/src/main/java/net/bramp/ffmpeg/builder/ChapterMetadataSpec.java
+++ /dev/null
@@ -1,16 +0,0 @@
-package net.bramp.ffmpeg.builder;
-
-public class ChapterMetadataSpec extends MetadataSpec {
-
-  public final int index;
-
-  protected ChapterMetadataSpec(int index) {
-    super(Type.Chapter);
-    this.index = index;
-  }
-
-  @Override
-  public String toString() {
-    return "c:" + index;
-  }
-}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java b/src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java
index dcaa3455..243f3679 100644
--- a/src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java
+++ b/src/main/java/net/bramp/ffmpeg/builder/FFmpegOutputBuilder.java
@@ -11,7 +11,6 @@
 import net.bramp.ffmpeg.probe.FFmpegProbeResult;
 import org.apache.commons.lang3.SystemUtils;
 import org.apache.commons.lang3.math.Fraction;
-import org.apache.commons.lang3.tuple.ImmutablePair;
 
 import java.net.URI;
 import java.util.List;
@@ -22,6 +21,7 @@
 import static com.google.common.base.Preconditions.checkState;
 import static net.bramp.ffmpeg.FFmpegUtils.millisecondsToString;
 import static com.google.common.base.Preconditions.checkNotNull;
+import static net.bramp.ffmpeg.builder.MetadataSpecifier.checkValidKey;
 
 /**
  * Builds a representation of a single output/encoding setting
@@ -303,17 +303,49 @@ public FFmpegOutputBuilder setComplexVideoFilter(String filter) {
    * @return this
    */
   public FFmpegOutputBuilder addMetaTag(String key, String value) {
-    checkNotNull(key, "Key may not be null");
-    checkNotNull(value, "Value may not be null");
-    meta_tags.add(key + "=" + value.replace("\"", ""));
+    checkValidKey(key);
+    checkNotNull(value);
+    meta_tags.add("-metadata");
+    meta_tags.add(key + "=" + value);
     return this;
   }
 
-
-  public FFmpegOutputBuilder addMetaTag(MetadataSpec metadata_spec, String key, String value) {
-    checkNotNull(key, "Key may not be null");
-    checkNotNull(value, "Value may not be null");
-    meta_tags.add(key + "=" + value.replace("\"", ""));
+  /**
+   * Add metadata on output streams. Which keys are possible depends on the used codec.
+   *
+   * <pre>
+   * {@code
+   * import static net.bramp.ffmpeg.builder.MetadataSpecifier.*;
+   * import static net.bramp.ffmpeg.builder.StreamSpecifier.*;
+   * import static net.bramp.ffmpeg.builder.StreamSpecifierType.*;
+   * 
+   * new FFmpegBuilder()
+   *   .addMetaTag("title", "Movie Title") // Annotate whole file
+   *   .addMetaTag(chapter(0), "author", "Bob") // Annotate first chapter
+   *   .addMetaTag(program(0), "comment", "Awesome") // Annotate first program
+   *   .addMetaTag(stream(0), "copyright", "Megacorp") // Annotate first stream
+   *   .addMetaTag(stream(Video), "framerate", "24fps") // Annotate all video streams
+   *   .addMetaTag(stream(Video, 0), "artist", "Joe") // Annotate first video stream
+   *   .addMetaTag(stream(Audio, 0), "language", "eng") // Annotate first audio stream
+   *   .addMetaTag(stream(Subtitle, 0), "language", "fre") // Annotate first subtitle stream
+   *   .addMetaTag(usable(), "year", "2010") // Annotate all streams with a usable configuration
+   * }
+   * </pre>
+   *
+   * assertThat(global().spec(), is("g")); assertThat(chapter(1).spec(), is("c:1"));
+   * assertThat(program(1).spec(), is("p:1")); assertThat(stream(1).spec(), is("s:1"));
+   * assertThat(stream(id(1)).spec(), is("s:i:1"));
+   *
+   * @param spec Metadata specifier, e.g `MetadataSpec.stream(Audio, 0)`
+   * @param key Metadata key, e.g. "comment"
+   * @param value Value to set for key
+   * @return this
+   */
+  public FFmpegOutputBuilder addMetaTag(MetadataSpecifier spec, String key, String value) {
+    checkValidKey(key);
+    checkNotNull(value);
+    meta_tags.add("-metadata:" + spec.spec());
+    meta_tags.add(key + "=" + value);
     return this;
   }
 
@@ -526,7 +558,7 @@ protected List<String> build(int pass) {
     }
 
     for (String meta : meta_tags) {
-      args.add("-metadata").add("\"" + meta + "\"");
+      args.add(meta);
     }
 
     if (video_enabled) {
diff --git a/src/main/java/net/bramp/ffmpeg/builder/GlobalMetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/GlobalMetadataSpec.java
deleted file mode 100644
index cf3153f7..00000000
--- a/src/main/java/net/bramp/ffmpeg/builder/GlobalMetadataSpec.java
+++ /dev/null
@@ -1,15 +0,0 @@
-package net.bramp.ffmpeg.builder;
-
-public class GlobalMetadataSpec extends MetadataSpec {
-
-  protected final static GlobalMetadataSpec SINGLETON = new GlobalMetadataSpec();
-
-  protected GlobalMetadataSpec() {
-    super(Type.Global);
-  }
-
-  @Override
-  public String toString() {
-    return "g";
-  }
-}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/MetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/MetadataSpec.java
deleted file mode 100644
index 4117cf29..00000000
--- a/src/main/java/net/bramp/ffmpeg/builder/MetadataSpec.java
+++ /dev/null
@@ -1,48 +0,0 @@
-package net.bramp.ffmpeg.builder;
-
-// metadata_spec can be:
-// g global (If metadata specifier is omitted, it defaults to global.)
-// s[:stream_spec]
-// c:chapter_index
-// p:program_index
-// index is meant to be zero based, by negitive is allowed as dummy values
-
-
-/**
- * Metadata spec, as described in the "map_metadata" section of
- * https://www.ffmpeg.org/ffmpeg-all.html#Main-options
- */
-public abstract class MetadataSpec {
-
-  enum Type {
-    Global, Stream, Chapter, Program
-  }
-
-  public final Type type;
-
-  protected MetadataSpec(Type type) {
-    this.type = type;
-  }
-
-  public abstract String toString();
-
-  public static GlobalMetadataSpec global() {
-    return GlobalMetadataSpec.SINGLETON;
-  }
-
-  public static ChapterMetadataSpec chapter(int index) {
-    return new ChapterMetadataSpec(index);
-  }
-
-  public static ProgramMetadataSpec program(int index) {
-    return new ProgramMetadataSpec(index);
-  }
-
-  public static StreamMetadataSpec stream(StreamSpec spec) {
-    return new StreamMetadataSpec(spec);
-  }
-
-  public static StreamMetadataSpec stream(int spec) {
-    return new StreamMetadataSpec(spec);
-  }
-}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/MetadataSpecifier.java b/src/main/java/net/bramp/ffmpeg/builder/MetadataSpecifier.java
new file mode 100644
index 00000000..a49064a8
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/MetadataSpecifier.java
@@ -0,0 +1,76 @@
+package net.bramp.ffmpeg.builder;
+
+// metadata_spec can be:
+// g global (If metadata specifier is omitted, it defaults to global.)
+// s[:stream_spec]
+// c:chapter_index
+// p:program_index
+// index is meant to be zero based, by negitive is allowed as dummy values
+
+
+import com.google.common.base.CharMatcher;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Metadata spec, as described in the "map_metadata" section of
+ * https://www.ffmpeg.org/ffmpeg-all.html#Main-options
+ */
+public class MetadataSpecifier {
+
+  final String spec;
+
+  private MetadataSpecifier(String spec) {
+    this.spec = checkNotNull(spec);
+  }
+
+  private MetadataSpecifier(String prefix, int index) {
+    this.spec = checkNotNull(prefix) + ":" + index;
+  }
+
+  private MetadataSpecifier(String prefix, StreamSpecifier spec) {
+    this.spec = checkNotNull(prefix) + ":" + checkNotNull(spec).spec();
+  }
+
+  public String spec() {
+    return spec;
+  }
+
+  public static String checkValidKey(String key) {
+    checkNotNull(key);
+    checkArgument(!key.isEmpty(), "key must not be empty");
+    checkArgument(key.matches("[a-zA-Z0-9_]+"), "key must only contain letters, numbers, and _");
+    return key;
+  }
+
+  public static MetadataSpecifier global() {
+    return new MetadataSpecifier("g");
+  }
+
+  public static MetadataSpecifier chapter(int index) {
+    return new MetadataSpecifier("c", index);
+  }
+
+  public static MetadataSpecifier program(int index) {
+    return new MetadataSpecifier("p", index);
+  }
+
+  public static MetadataSpecifier stream(int index) {
+    return new MetadataSpecifier("s", StreamSpecifier.stream(index));
+  }
+
+  public static MetadataSpecifier stream(StreamSpecifierType type) {
+    return new MetadataSpecifier("s", StreamSpecifier.stream(type));
+  }
+
+  public static MetadataSpecifier stream(StreamSpecifierType stream_type, int stream_index) {
+    return new MetadataSpecifier("s", StreamSpecifier.stream(stream_type, stream_index));
+  }
+
+  public static MetadataSpecifier stream(StreamSpecifier spec) {
+    checkNotNull(spec);
+    return new MetadataSpecifier("s", spec);
+  }
+
+}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/ProgramMetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/ProgramMetadataSpec.java
deleted file mode 100644
index 46d3c362..00000000
--- a/src/main/java/net/bramp/ffmpeg/builder/ProgramMetadataSpec.java
+++ /dev/null
@@ -1,16 +0,0 @@
-package net.bramp.ffmpeg.builder;
-
-public class ProgramMetadataSpec extends MetadataSpec {
-
-  public final int index;
-
-  protected ProgramMetadataSpec(int index) {
-    super(Type.Program);
-    this.index = index;
-  }
-
-  @Override
-  public String toString() {
-    return "p:" + index;
-  }
-}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/StreamMetadataSpec.java b/src/main/java/net/bramp/ffmpeg/builder/StreamMetadataSpec.java
deleted file mode 100644
index 24d37029..00000000
--- a/src/main/java/net/bramp/ffmpeg/builder/StreamMetadataSpec.java
+++ /dev/null
@@ -1,18 +0,0 @@
-package net.bramp.ffmpeg.builder;
-
-import static com.google.common.base.Preconditions.checkNotNull;
-
-public class StreamMetadataSpec extends MetadataSpec {
-
-  public final StreamSpec spec;
-
-  protected StreamMetadataSpec(StreamSpec spec) {
-    super(Type.Stream);
-    this.spec = checkNotNull(spec);
-  }
-
-  @Override
-  public String toString() {
-    return "s:" + spec.toString();
-  }
-}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/StreamSpec.java b/src/main/java/net/bramp/ffmpeg/builder/StreamSpec.java
deleted file mode 100644
index 1300f41f..00000000
--- a/src/main/java/net/bramp/ffmpeg/builder/StreamSpec.java
+++ /dev/null
@@ -1,135 +0,0 @@
-package net.bramp.ffmpeg.builder;
-
-import static com.google.common.base.Preconditions.checkNotNull;
-
-/**
- * https://ffmpeg.org/ffmpeg.html#Stream-specifiers
- */
-public abstract class StreamSpec {
-
-  enum Type {
-    StreamIndex, Program, StreamId, Metadata, Usable
-  }
-
-  enum StreamType {
-    Any(""),
-    Video("v"),
-    PureVideo("V"),
-    Audio("a"),
-    Subtiles("s"),
-    Data("d"),
-    Attachments("t");
-
-    final String prefix;
-
-    StreamType(String prefix) {
-      this.prefix = prefix;
-    }
-
-    public String toString() {
-      return prefix;
-    }
-  }
-
-  public final Type type;
-
-  protected StreamSpec(Type type) {
-    this.type = type;
-  }
-
-  public static class IndexStreamSpec extends StreamSpec {
-
-  }
-
-  public static class ProgramStreamSpec extends StreamSpec {
-
-  }
-
-  public static class IdStreamSpec extends StreamSpec {
-
-  }
-
-  public static class MetadataStreamSpec extends StreamSpec {
-
-    public final String key, value;
-
-    protected MetadataStreamSpec(String key, String value) {
-      super(Type.Metadata);
-      this.key = checkNotNull(key);
-      this.value = value;
-    }
-
-    @Override
-    public String toString() {
-      return "m:" + key + (value != null ? ":" + value : "");
-    }
-  }
-
-  public static class UsableStreamSpec extends StreamSpec {
-    protected final static UsableStreamSpec SINGLETON = new UsableStreamSpec();
-
-    protected UsableStreamSpec() {
-      super(Type.Usable);
-    }
-
-    @Override
-    public String toString() {
-      return "u";
-    }
-  }
-
-  public abstract String toString();
-
-  public StreamSpec stream(int stream_index) {
-    return null;
-  }
-
-  public StreamSpec stream(StreamType stream_type) {
-    checkNotNull(stream_type);
-    return null;
-  }
-
-  public StreamSpec stream(StreamType stream_type, int stream_index) {
-    checkNotNull(stream_type);
-    return null;
-  }
-
-  public StreamSpec program(int program_id) {
-    return null;
-  }
-
-  public StreamSpec program(int program_id, int stream_index) {
-    return null;
-  }
-
-  public StreamSpec id(int stream_id) {
-    return null;
-  }
-
-  public StreamSpec tag(String key) {
-    checkNotNull(key);
-    return null;
-  }
-
-  public StreamSpec tag(String key, String value) {
-    checkNotNull(key);
-    checkNotNull(value);
-    return null;
-  }
-
-  public StreamSpec usable() {
-    return UsableStreamSpec.SINGLETON;
-  }
-}
-
-
-// metadata_spec can be:
-// g global (If metadata specifier is omitted, it defaults to global.)
-// s[:stream_spec]
-// c:chapter_index
-// p:program_index
-// index is meant to be zero based, by negitive is allowed as dummy values
-/*
- * public abstract class MetadataSpec { global() stream(index(0)) stream(video(), index(0))
- * chapter(1) program(1) }
- */
diff --git a/src/main/java/net/bramp/ffmpeg/builder/StreamSpecifier.java b/src/main/java/net/bramp/ffmpeg/builder/StreamSpecifier.java
new file mode 100644
index 00000000..419f27e6
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/StreamSpecifier.java
@@ -0,0 +1,118 @@
+package net.bramp.ffmpeg.builder;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static net.bramp.ffmpeg.builder.MetadataSpecifier.checkValidKey;
+
+/**
+ *
+ * https://ffmpeg.org/ffmpeg.html#Stream-specifiers
+ */
+public class StreamSpecifier {
+
+  final String spec;
+
+  private StreamSpecifier(String spec) {
+    this.spec = spec;
+  }
+
+  public String spec() {
+    return spec;
+  }
+
+  /**
+   * Matches the stream with this index.
+   * 
+   * @param index
+   * @return
+   */
+  public static StreamSpecifier stream(int index) {
+    return new StreamSpecifier(String.valueOf(index));
+  }
+
+  /**
+   * Matches all streams of this type.
+   * 
+   * @param type
+   * @return
+   */
+  public static StreamSpecifier stream(StreamSpecifierType type) {
+    checkNotNull(type);
+    return new StreamSpecifier(type.toString());
+  }
+
+  /**
+   * Matches the stream number stream_index of this type.
+   * 
+   * @param type
+   * @param index
+   * @return
+   */
+  public static StreamSpecifier stream(StreamSpecifierType type, int index) {
+    checkNotNull(type);
+    return new StreamSpecifier(type.toString() + ":" + index);
+  }
+
+  /**
+   * Matches all streams in the program.
+   * 
+   * @param program_id
+   * @return
+   */
+  public static StreamSpecifier program(int program_id) {
+    return new StreamSpecifier("p:" + program_id);
+  }
+
+  /**
+   * Matches the stream with number stream_index in the program with the id program_id.
+   * 
+   * @param program_id
+   * @param stream_index
+   * @return
+   */
+  public static StreamSpecifier program(int program_id, int stream_index) {
+    return new StreamSpecifier("p:" + program_id + ":" + stream_index);
+  }
+
+  /**
+   * Match the stream by stream id (e.g. PID in MPEG-TS container).
+   *
+   * @param stream_id
+   * @return
+   */
+  public static StreamSpecifier id(int stream_id) {
+    return new StreamSpecifier("i:" + stream_id);
+  }
+
+  /**
+   * Matches all streams with the given metadata tag.
+   * 
+   * @param key
+   * @return
+   */
+  public static StreamSpecifier tag(String key) {
+    return new StreamSpecifier("m:" + checkValidKey(key));
+  }
+
+  /**
+   * Matches streams with the metadata tag key having the specified value.
+   * 
+   * @param key
+   * @param value
+   * @return
+   */
+  public static StreamSpecifier tag(String key, String value) {
+    checkValidKey(key);
+    checkNotNull(value);
+    return new StreamSpecifier("m:" + key + ":" + value);
+  }
+
+  /**
+   * Matches streams with usable configuration, the codec must be defined and the essential
+   * information such as video dimension or audio sample rate must be present.
+   * 
+   * @return
+   */
+  public static StreamSpecifier usable() {
+    return new StreamSpecifier("u");
+  }
+}
diff --git a/src/main/java/net/bramp/ffmpeg/builder/StreamSpecifierType.java b/src/main/java/net/bramp/ffmpeg/builder/StreamSpecifierType.java
new file mode 100644
index 00000000..83b09fb9
--- /dev/null
+++ b/src/main/java/net/bramp/ffmpeg/builder/StreamSpecifierType.java
@@ -0,0 +1,43 @@
+package net.bramp.ffmpeg.builder;
+
+public enum StreamSpecifierType {
+  /**
+   * Video
+   */
+  Video("v"),
+
+  /**
+   * Video streams which are not attached pictures, video thumbnails or cover arts.
+   */
+  PureVideo("V"),
+
+  /**
+   * Audio
+   */
+  Audio("a"),
+
+  /**
+   * Subtitles
+   */
+  Subtitle("s"),
+
+  /**
+   * Data
+   */
+  Data("d"),
+
+  /**
+   * Attachment
+   */
+  Attachment("t");
+
+  final String prefix;
+
+  StreamSpecifierType(String prefix) {
+    this.prefix = prefix;
+  }
+
+  public String toString() {
+    return prefix;
+  }
+}
diff --git a/src/test/java/net/bramp/ffmpeg/builder/FFmpegBuilderTest.java b/src/test/java/net/bramp/ffmpeg/builder/FFmpegBuilderTest.java
index edc268cc..b8186eaf 100644
--- a/src/test/java/net/bramp/ffmpeg/builder/FFmpegBuilderTest.java
+++ b/src/test/java/net/bramp/ffmpeg/builder/FFmpegBuilderTest.java
@@ -1,7 +1,7 @@
 package net.bramp.ffmpeg.builder;
 
+import com.google.common.base.Joiner;
 import net.bramp.ffmpeg.FFmpeg;
-import net.bramp.ffmpeg.builder.FFmpegBuilder;
 import net.bramp.ffmpeg.options.AudioEncodingOptions;
 import net.bramp.ffmpeg.options.EncodingOptions;
 import net.bramp.ffmpeg.options.MainEncodingOptions;
@@ -14,6 +14,12 @@
 import java.util.concurrent.TimeUnit;
 
 import static com.nitorcreations.Matchers.reflectEquals;
+import static net.bramp.ffmpeg.builder.MetadataSpecifier.chapter;
+import static net.bramp.ffmpeg.builder.MetadataSpecifier.program;
+import static net.bramp.ffmpeg.builder.MetadataSpecifier.stream;
+import static net.bramp.ffmpeg.builder.StreamSpecifier.tag;
+import static net.bramp.ffmpeg.builder.StreamSpecifier.usable;
+import static net.bramp.ffmpeg.builder.StreamSpecifierType.*;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
 
@@ -173,16 +179,45 @@ public void testMetaTags() {
     List<String> args = new FFmpegBuilder()
         .setInput("input")
         .addOutput("output")
-          .disableAudio()
-          .disableSubtitle()
           .addMetaTag("comment", "My Comment")
           .addMetaTag("title", "\"Video\"")
+          .addMetaTag("author", "a=b:c")
+          .done()
+        .build();
+    // @formatter:on
+
+    assertThat(args,
+        is(Arrays.asList("-y", "-v", "error", "-i", "input", "-metadata", "comment=My Comment",
+            "-metadata", "title=\"Video\"", "-metadata", "author=a=b:c", "output")));
+  }
+
+  @Test
+  public void testMetaTagsWithSpecifier() {
+    // @formatter:off
+    List<String> args = new FFmpegBuilder()
+        .setInput("input")
+        .addOutput("output")
+          .addMetaTag("title", "Movie Title")
+          .addMetaTag(chapter(0), "author", "Bob")
+          .addMetaTag(program(0), "comment", "Awesome")
+          .addMetaTag(stream(0), "copyright", "Megacorp")
+          .addMetaTag(stream(Video), "framerate", "24fps")
+          .addMetaTag(stream(Video, 0), "artist", "Joe")
+          .addMetaTag(stream(Audio, 0), "language", "eng")
+          .addMetaTag(stream(Subtitle, 0), "language", "fre")
+          .addMetaTag(stream(usable()), "year", "2010")
+          .addMetaTag(stream(tag("key")), "a", "b")
+          .addMetaTag(stream(tag("key", "value")), "a", "b")
           .done()
         .build();
     // @formatter:on
 
     assertThat(args, is(Arrays.asList("-y", "-v", "error", "-i", "input", "-metadata",
-        "\"comment=My Comment\"", "-metadata", "\"title=Video\"", "-an", "-sn", "output")));
+        "title=Movie Title", "-metadata:c:0", "author=Bob", "-metadata:p:0", "comment=Awesome",
+        "-metadata:s:0", "copyright=Megacorp", "-metadata:s:v", "framerate=24fps",
+        "-metadata:s:v:0", "artist=Joe", "-metadata:s:a:0", "language=eng", "-metadata:s:s:0",
+        "language=fre", "-metadata:s:u", "year=2010", "-metadata:s:m:key", "a=b",
+        "-metadata:s:m:key:value", "a=b", "output")));
   }
 
   @Test
diff --git a/src/test/java/net/bramp/ffmpeg/builder/MetadataSpecTest.java b/src/test/java/net/bramp/ffmpeg/builder/MetadataSpecTest.java
index 5403fa58..2f7e19b3 100644
--- a/src/test/java/net/bramp/ffmpeg/builder/MetadataSpecTest.java
+++ b/src/test/java/net/bramp/ffmpeg/builder/MetadataSpecTest.java
@@ -2,7 +2,8 @@
 
 import org.junit.Test;
 
-import static net.bramp.ffmpeg.builder.MetadataSpec.*;
+import static net.bramp.ffmpeg.builder.MetadataSpecifier.*;
+import static net.bramp.ffmpeg.builder.StreamSpecifier.id;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.*;
 
@@ -10,9 +11,10 @@ public class MetadataSpecTest {
 
   @Test
   public void testMetaSpec() {
-    assertThat(global().toString(), is("g"));
-    assertThat(chapter(1).toString(), is("c:1"));
-    assertThat(program(1).toString(), is("p:1"));
-    assertThat(stream(1).toString(), is("s:1"));
+    assertThat(global().spec(), is("g"));
+    assertThat(chapter(1).spec(), is("c:1"));
+    assertThat(program(1).spec(), is("p:1"));
+    assertThat(stream(1).spec(), is("s:1"));
+    assertThat(stream(id(1)).spec(), is("s:i:1"));
   }
 }
diff --git a/src/test/java/net/bramp/ffmpeg/builder/StreamSpecTest.java b/src/test/java/net/bramp/ffmpeg/builder/StreamSpecTest.java
index c93328e7..8206c1f0 100644
--- a/src/test/java/net/bramp/ffmpeg/builder/StreamSpecTest.java
+++ b/src/test/java/net/bramp/ffmpeg/builder/StreamSpecTest.java
@@ -1,6 +1,9 @@
 package net.bramp.ffmpeg.builder;
 
-import static net.bramp.ffmpeg.builder.MetadataSpec.stream;
+import org.junit.Test;
+
+import static net.bramp.ffmpeg.builder.StreamSpecifier.*;
+import static net.bramp.ffmpeg.builder.StreamSpecifierType.*;
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.*;
 
@@ -8,21 +11,23 @@ public class StreamSpecTest {
 
   @Test
   public void testStreamSpec() {
-    assertThat(stream(1).toString(), is("1"));
-    assertThat(stream(VIDEO, 1).toString(), is("v:1"));
+    assertThat(stream(1).spec(), is("1"));
+    assertThat(stream(Video).spec(), is("v"));
 
-    assertThat(chapter(1).toString(), is("c:1"));
-    assertThat(program(1).toString(), is("p:1"));
-  }
+    assertThat(stream(Video, 1).spec(), is("v:1"));
+    assertThat(stream(PureVideo, 1).spec(), is("V:1"));
+    assertThat(stream(Audio, 1).spec(), is("a:1"));
+    assertThat(stream(Subtitle, 1).spec(), is("s:1"));
+    assertThat(stream(Data, 1).spec(), is("d:1"));
+    assertThat(stream(Attachment, 1).spec(), is("t:1"));
 
-  addMetaTag("key", "value", );
-  addMetaTag("key", "value", chapter(1));
-  addMetaTag("key", "value", program(1));
-  addMetaTag("key", "value", stream(0));
-  addMetaTag("key", "value", stream(VIDEO, 0);
-  addMetaTag("key", "value", stream(AUDIO, 0);
-  addMetaTag("key", "value", stream(id(0x502));
-  addMetaTag("key", "value", stream(tag("key2", "value2"))); // This one is confusing, key2 refers to the output stream, and would apply key/value to any output stream already with key2/value2.
-  */
-}
+    assertThat(program(1).spec(), is("p:1"));
+    assertThat(program(1, 2).spec(), is("p:1:2"));
+
+    assertThat(id(1).spec(), is("i:1"));
+
+    assertThat(tag("key").spec(), is("m:key"));
+    assertThat(tag("key", "value").spec(), is("m:key:value"));
+    assertThat(usable().spec(), is("u"));
+  }
 }