1 files changed, 127 insertions, 0 deletions
diff --git a/app/src/main/java/github/daneren2005/dsub/util/tags/OpusFile.java b/app/src/main/java/github/daneren2005/dsub/util/tags/OpusFile.java
new file mode 100644
index 00000000..38b402bb
--- /dev/null
+++ b/app/src/main/java/github/daneren2005/dsub/util/tags/OpusFile.java
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2015 Adrian Ulrich <adrian@blinkenlights.ch>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>. 
+ */
+package github.daneren2005.dsub.util.tags;
+
+
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.util.HashMap;
+
+
+public class OpusFile extends OggFile {
+	// A list of tags we are going to ignore in the OpusTags section
+	public static final String[] FORBIDDEN_TAGS = {"REPLAYGAIN_TRACK_GAIN", "REPLAYGAIN_TRACK_PEAK", "REPLAYGAIN_ALBUM_GAIN", "REPLAYGAIN_ALBUM_PEAK"};
+
+	public OpusFile() {
+	}
+
+	public HashMap getTags(RandomAccessFile s) throws IOException {
+
+		// The opus specification is very strict: The first packet MUST
+		// contain the OpusHeader while the 2nd MUST contain the
+		// OggHeader payload: https://wiki.xiph.org/OggOpus
+		long pos = 0;
+		PageInfo pi =  parse_stream_page(s, pos);
+
+		HashMap tags = new HashMap();
+		HashMap opus_head = parse_opus_head(s, pos+pi.header_len, pi.payload_len);
+		pos += pi.header_len+pi.payload_len;
+
+		// Check if we parsed a version number and ensure it doesn't have any
+		// of the upper 4 bits set (eg: <= 15)
+		if(opus_head.containsKey("version") && (Integer)opus_head.get("version") <= 0xF) {
+			// Get next page: The spec requires this to be an OpusTags head
+			pi = parse_stream_page(s, pos);
+			tags = parse_opus_vorbis_comment(s, pos+pi.header_len, pi.payload_len);
+			// ...and merge replay gain intos into the tags map
+			calculate_gain(opus_head, tags);
+		}
+
+		return tags;
+	}
+
+	/**
+	 * Adds replay gain information to the tags hash map
+	 */
+	private void calculate_gain(HashMap header, HashMap tags) {
+		// Remove any unacceptable tags (Opus files must not have
+		// their own REPLAYGAIN_* fields)
+		for(String k : FORBIDDEN_TAGS) {
+			tags.remove(k);
+		}
+		// Include the gain value found in the opus header
+		int header_gain = (Integer)header.get("header_gain");
+		addTagEntry(tags, "R128_BASTP_BASE_GAIN", ""+header_gain);
+	}
+
+
+	/**
+	 * Attempts to parse an OpusHead block at given offset.
+	 * Returns an hash-map, will be empty on failure
+	 */
+	private HashMap parse_opus_head(RandomAccessFile s, long offset, long pl_len) throws IOException {
+		/* Structure:
+		 * 8 bytes of 'OpusHead'
+		 * 1 byte  version
+		 * 1 byte  channel count
+		 * 2 bytes pre skip
+		 * 4 bytes input-sample-rate
+		 * 2 bytes outputGain as Q7.8
+		 * 1 byte  channel map
+		 * --> 19 bytes
+		 */
+
+		HashMap id_hash = new HashMap();
+		byte[] buff = new byte[19];
+		if(pl_len >= buff.length) {
+			s.seek(offset);
+			s.read(buff);
+			if((new String(buff, 0, 8)).equals("OpusHead")) {
+				id_hash.put("version"      , b2u(buff[8]));
+				id_hash.put("channels"     , b2u(buff[9]));
+				id_hash.put("pre_skip"     , b2le16(buff, 10));
+				id_hash.put("sampling_rate", b2le32(buff, 12));
+				id_hash.put("header_gain"  , (int)((short)b2le16(buff, 16)));
+				id_hash.put("channel_map"  , b2u(buff[18]));
+			}
+		}
+
+		return id_hash;
+	}
+
+	/**
+	 * Parses an OpusTags section
+	 * Returns a hash map of the found tags
+	 */
+	private HashMap parse_opus_vorbis_comment(RandomAccessFile s, long offset, long pl_len) throws IOException {
+		final int magic_len = 8; // OpusTags
+		byte[] magic = new byte[magic_len];
+
+		if(pl_len < magic_len)
+			xdie("opus comment field is too short!");
+
+		// Read and check magic signature
+		s.seek(offset);
+		s.read(magic);
+
+		if((new String(magic, 0, magic_len)).equals("OpusTags") == false)
+			xdie("Damaged packet found!");
+
+		return parse_vorbis_comment(s, this, offset+magic_len, pl_len-magic_len);
+	}
+
+}