| // Copyright 2024 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef MEDIA_FORMATS_MP4_AC3_CONSTANTS_H_ |
| #define MEDIA_FORMATS_MP4_AC3_CONSTANTS_H_ |
| |
| #include <stdint.h> |
| |
| #include "media/base/channel_layout.h" |
| #include "media/base/media_export.h" |
| |
| namespace media { |
| |
| // Please refer to ETSI TS 102 366 V1.4.1 |
| // https://www.etsi.org/deliver/etsi_ts/102300_102399/102366/01.03.01_60/ts_102366v010301p.pdf |
| // for more details. |
| // |
| // F.6.2.13 chan_loc - 9bit - Table F.6.1 - chan_loc field bit assignments. |
| // |
| // The chan_loc field indicates channel locations (beyond the standard 5.1 |
| // channels) that are carried by dependent substreams associated with an |
| // independent substream. |
| enum EC3DependentSubstreamChannelLocation { |
| LC_RC = 1, // Lc/Rc pair |
| LRS_RRS = 2, // Lrs/Rrs pair |
| CS = 4, // Cs |
| TS = 8, // Ts |
| LSD_RSD = 16, // Lsd/Rsd pair |
| LW_RW = 32, // Lw/Rw pair |
| LVH_RVH = 64, // Lvh/Rvh pair |
| CVH = 128, // Cvh |
| LFE2 = 256, // LFE2 |
| }; |
| |
| // F.4.2.6 lfeon - Low frequency effects channel on - 1 bit |
| // |
| // Size of the lfeon field, used to determine if the lfe (sub woofer) |
| // channel exists or not. |
| MEDIA_EXPORT inline constexpr uint8_t kAC3LFESize = 2; |
| |
| // 4.4.2.3 acmod - Audio coding mode - 3 bits. |
| // |
| // Size of the acmod field, used to indicates which of the main service |
| // channels are in use, ranging from 3/2 to 1/0 |
| MEDIA_EXPORT inline constexpr uint8_t kAC3AudioCodingModeSize = 8; |
| |
| // Conversion table of channel layout, the first dimension is lfeon and the |
| // second dimension is acmod. |
| // |
| // Taking the 5.1 channel layout as an example, it contains a LFE channel, so |
| // lfeon = 1, and the remaining five channels are: L, C, R, Ls, Rs with acmod = |
| // 7, so kAC3AudioCodingModeTable[1][7] = CHANNEL_LAYOUT_5_1. |
| MEDIA_EXPORT extern const ChannelLayout |
| kAC3AudioCodingModeTable[kAC3LFESize][kAC3AudioCodingModeSize]; |
| |
| } // namespace media |
| |
| #endif // MEDIA_FORMATS_MP4_AC3_CONSTANTS_H_ |
