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/*
* 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);
}
}
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