Update WebmMuxer for audio component of MediaStream recording.

media/filters/opus_constants.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_FILTERS_OPUS_CONSTANTS_H_
+#define MEDIA_FILTERS_OPUS_CONSTANTS_H_
+
+namespace media {
+
+// The Opus specification is part of IETF RFC 6716:
+// http://tools.ietf.org/html/rfc6716
+
+// Opus Extra Data contents:
+// - "OpusHead" magic signature (64 bits)
+// - version number (8 bits)
+// - Channels C (8 bits)
+// - Pre-skip (16 bits)
+// - Sampling rate (32 bits)
+// - Gain in dB (16 bits, S7.8)
+// - Mapping (8 bits, 0=single stream (mono/stereo) 1=Vorbis mapping,
+//            2..254: reserved, 255: multistream with no mapping)
+//
+// - if (mapping != 0)
+//    - N = total number of streams (8 bits)
+//    - M = number of paired streams (8 bits)
+//    - C times channel origin
+//         - if (C<2*M)
+//            - stream = byte/2
+//            - if (byte&0x1 == 0)
+//                - left
+//              else
+//                - right
+//         - else
+//            - stream = byte-M
+
+enum {
+  // Default audio output channel layout. Used to initialize |stream_map| in
+  // OpusExtraData, and passed to opus_multistream_decoder_create() when the
+  // extra data does not contain mapping information. The values are valid only
+  // for mono and stereo output: Opus streams with more than 2 channels require
+  // a stream map.
+  OPUS_MAX_CHANNELS_WITH_DEFAULT_LAYOUT = 2,
+
+  // Opus uses Vorbis channel mapping, and Vorbis channel mapping specifies
+  // mappings for up to 8 channels. This information is part of the Vorbis I
+  // Specification:
+  // http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html
+  OPUS_MAX_VORBIS_CHANNELS = 8,
+
+  // Size of the Opus extra data excluding optional mapping information.
+  OPUS_EXTRADATA_SIZE = 19,
+  // Offset for magic signature "OpusHead"
+  OPUS_EXTRADATA_LABEL_OFFSET = 0,
+  // Offset to the Opus version number
+  OPUS_EXTRADATA_VERSION_OFFSET = 8,
+  // Offset to the channel count byte in the Opus extra data
+  OPUS_EXTRADATA_CHANNELS_OFFSET = 9,
+  // Offset to the pre-skip value in the Opus extra data
+  OPUS_EXTRADATA_SKIP_SAMPLES_OFFSET = 10,
+  // Offset to the sampling rate value in the Opus extra data
+  OPUS_EXTRADATA_SAMPLE_RATE_OFFSET = 12,
+  // Offset to the gain value in the Opus extra data
+  OPUS_EXTRADATA_GAIN_OFFSET = 16,
+  // Offset to the channel mapping byte in the Opus extra data
+  OPUS_EXTRADATA_CHANNEL_MAPPING_OFFSET = 18,
+
+  // Extra Data contains a stream map, beyond the always present
+  // |OPUS_EXTRADATA_SIZE| bytes of data. The mapping data contains stream
+  // count, coupling information, and per channel mapping values:
+  //   - Byte 0: Number of streams.
+  //   - Byte 1: Number coupled.
+  //   - Byte 2: Starting at byte 2 are |extra_data->channels| uint8 mapping
+  //             values.
+  OPUS_EXTRADATA_NUM_STREAMS_OFFSET = OPUS_EXTRADATA_SIZE,
+  OPUS_EXTRADATA_NUM_COUPLED_OFFSET = OPUS_EXTRADATA_NUM_STREAMS_OFFSET + 1,
+  OPUS_EXTRADATA_STREAM_MAP_OFFSET = OPUS_EXTRADATA_NUM_STREAMS_OFFSET + 2,
+};
+
+// Vorbis channel ordering for streams with >= 2 channels:
+// 2 Channels
+//   L, R
+// 3 Channels
+//   L, Center, R
+// 4 Channels
+//   Front L, Front R, Back L, Back R
+// 5 Channels
+//   Front L, Center, Front R, Back L, Back R
+// 6 Channels (5.1)
+//   Front L, Center, Front R, Back L, Back R, LFE
+// 7 channels (6.1)
+//   Front L, Front Center, Front R, Side L, Side R, Back Center, LFE
+// 8 Channels (7.1)
+//   Front L, Center, Front R, Side L, Side R, Back L, Back R, LFE
+//
+// Channel ordering information is taken from section 4.3.9 of the Vorbis I
+// Specification:
+// http://xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9
+extern const uint8_t
+    kDefaultOpusChannelLayout[OPUS_MAX_CHANNELS_WITH_DEFAULT_LAYOUT];
+
+// These are the FFmpeg channel layouts expressed using the position of each
+// channel in the output stream from libopus.
+extern const uint8_t kFFmpegChannelDecodingLayouts[OPUS_MAX_VORBIS_CHANNELS]
+                                                  [OPUS_MAX_VORBIS_CHANNELS];
+
+// Opus internal to Vorbis channel order mapping written in the header.
+extern const uint8_t
+    kOpusVorbisChannelMap[OPUS_MAX_VORBIS_CHANNELS][OPUS_MAX_VORBIS_CHANNELS];
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_OPUS_CONSTANTS_H_