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1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef MEDIA_FILTERS_OPUS_CONSTANTS_H_ | |
6 #define MEDIA_FILTERS_OPUS_CONSTANTS_H_ | |
7 | |
8 namespace media { | |
9 | |
10 // The Opus specification is part of IETF RFC 6716: | |
11 // http://tools.ietf.org/html/rfc6716 | |
12 | |
13 // Opus Extra Data contents: | |
14 // - "OpusHead" magic signature (64 bits) | |
15 // - version number (8 bits) | |
16 // - Channels C (8 bits) | |
17 // - Pre-skip (16 bits) | |
18 // - Sampling rate (32 bits) | |
19 // - Gain in dB (16 bits, S7.8) | |
20 // - Mapping (8 bits, 0=single stream (mono/stereo) 1=Vorbis mapping, | |
21 // 2..254: reserved, 255: multistream with no mapping) | |
22 // | |
23 // - if (mapping != 0) | |
24 // - N = totel number of streams (8 bits) | |
25 // - M = number of paired streams (8 bits) | |
26 // - C times channel origin | |
27 // - if (C<2*M) | |
28 // - stream = byte/2 | |
29 // - if (byte&0x1 == 0) | |
30 // - left | |
31 // else | |
32 // - right | |
33 // - else | |
34 // - stream = byte-M | |
35 | |
36 enum { | |
37 // Default audio output channel layout. Used to initialize |stream_map| in | |
38 // OpusExtraData, and passed to opus_multistream_decoder_create() when the | |
39 // extra data does not contain mapping information. The values are valid only | |
40 // for mono and stereo output: Opus streams with more than 2 channels require | |
41 // a stream map. | |
42 OPUS_MAX_CHANNELS_WITH_DEFAULT_LAYOUT = 2, | |
43 | |
miu
2015/11/04 00:18:28
nit: Please remove extra newline.
ajose
2015/11/04 20:51:19
Done.
| |
44 | |
Tom Finegan
2015/11/04 00:28:55
nit: one line of whitespace is probably good here
ajose
2015/11/04 20:51:19
Done.
| |
45 // Opus uses Vorbis channel mapping, and Vorbis channel mapping specifies | |
46 // mappings for up to 8 channels. This information is part of the Vorbis I | |
47 // Specification: | |
48 // http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html | |
49 OPUS_MAX_VORBIS_CHANNELS = 8, | |
50 | |
51 // Size of the Opus extra data excluding optional mapping information. | |
52 OPUS_EXTRADATA_SIZE = 19, | |
53 // Offset for magic signature "OpusHead" | |
54 OPUS_EXTRADATA_LABEL_OFFSET = 0, | |
55 // Offset to the Opus version number | |
56 OPUS_EXTRADATA_VERSION_OFFSET = 8, | |
57 // Offset to the channel count byte in the Opus extra data | |
58 OPUS_EXTRADATA_CHANNELS_OFFSET = 9, | |
59 // Offset to the pre-skip value in the Opus extra data | |
60 OPUS_EXTRADATA_SKIP_SAMPLES_OFFSET = 10, | |
61 // Offset to the sampling rate value in the Opus extra data | |
62 OPUS_EXTRADATA_SAMPLE_RATE_OFFSET = 12, | |
63 // Offset to the gain value in the Opus extra data | |
64 OPUS_EXTRADATA_GAIN_OFFSET = 16, | |
65 // Offset to the channel mapping byte in the Opus extra data | |
66 OPUS_EXTRADATA_CHANNEL_MAPPING_OFFSET = 18, | |
67 | |
68 // Extra Data contains a stream map, beyond the always present | |
69 // |OPUS_EXTRADATA_SIZE| bytes of data. The mapping data contains stream | |
70 // count, coupling information, and per channel mapping values: | |
71 // - Byte 0: Number of streams. | |
72 // - Byte 1: Number coupled. | |
73 // - Byte 2: Starting at byte 2 are |extra_data->channels| uint8 mapping | |
74 // values. | |
75 OPUS_EXTRADATA_NUM_STREAMS_OFFSET = OPUS_EXTRADATA_SIZE, | |
76 OPUS_EXTRADATA_NUM_COUPLED_OFFSET = OPUS_EXTRADATA_NUM_STREAMS_OFFSET + 1, | |
77 OPUS_EXTRADATA_STREAM_MAP_OFFSET = OPUS_EXTRADATA_NUM_STREAMS_OFFSET + 2, | |
78 }; | |
79 | |
80 // Vorbis channel ordering for streams with >= 2 channels: | |
81 // 2 Channels | |
82 // L, R | |
83 // 3 Channels | |
84 // L, Center, R | |
85 // 4 Channels | |
86 // Front L, Front R, Back L, Back R | |
87 // 5 Channels | |
88 // Front L, Center, Front R, Back L, Back R | |
89 // 6 Channels (5.1) | |
90 // Front L, Center, Front R, Back L, Back R, LFE | |
91 // 7 channels (6.1) | |
92 // Front L, Front Center, Front R, Side L, Side R, Back Center, LFE | |
93 // 8 Channels (7.1) | |
94 // Front L, Center, Front R, Side L, Side R, Back L, Back R, LFE | |
95 // | |
96 // Channel ordering information is taken from section 4.3.9 of the Vorbis I | |
97 // Specification: | |
98 // http://xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9 | |
99 | |
miu
2015/11/04 00:18:28
nit: Please remove extra newline here too.
ajose
2015/11/04 20:51:19
Done.
| |
100 extern const uint8_t | |
101 kDefaultOpusChannelLayout[OPUS_MAX_CHANNELS_WITH_DEFAULT_LAYOUT]; | |
102 | |
103 // These are the FFmpeg channel layouts expressed using the position of each | |
104 // channel in the output stream from libopus. | |
105 extern const uint8_t kFFmpegChannelDecodingLayouts[OPUS_MAX_VORBIS_CHANNELS] | |
106 [OPUS_MAX_VORBIS_CHANNELS]; | |
107 | |
108 // Opus internal to Vorbis channel order mapping written in the header. | |
109 extern const uint8_t kOpusVorbisChannelMap[OPUS_MAX_VORBIS_CHANNELS] | |
110 [OPUS_MAX_VORBIS_CHANNELS]; | |
111 | |
112 } // namespace media | |
113 | |
114 #endif // MEDIA_FILTERS_OPUS_CONSTANTS_H_ | |
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