mov_chan.c
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1 /*
2  * Copyright (c) 2011 Justin Ruggles
3  *
4  * This file is part of Libav.
5  *
6  * Libav is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * Libav is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with Libav; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
26 #include <stdint.h>
27 
28 #include "libavutil/audioconvert.h"
29 #include "libavcodec/avcodec.h"
30 #include "mov_chan.h"
31 
48  MOV_CH_LAYOUT_UNKNOWN = 0xFFFF0000,
50  MOV_CH_LAYOUT_USE_BITMAP = ( 1 << 16) | 0,
51  MOV_CH_LAYOUT_DISCRETEINORDER = (147 << 16) | 0,
52  MOV_CH_LAYOUT_MONO = (100 << 16) | 1,
53  MOV_CH_LAYOUT_STEREO = (101 << 16) | 2,
54  MOV_CH_LAYOUT_STEREOHEADPHONES = (102 << 16) | 2,
55  MOV_CH_LAYOUT_MATRIXSTEREO = (103 << 16) | 2,
56  MOV_CH_LAYOUT_MIDSIDE = (104 << 16) | 2,
57  MOV_CH_LAYOUT_XY = (105 << 16) | 2,
58  MOV_CH_LAYOUT_BINAURAL = (106 << 16) | 2,
60  MOV_CH_LAYOUT_QUADRAPHONIC = (108 << 16) | 4,
61  MOV_CH_LAYOUT_PENTAGONAL = (109 << 16) | 5,
62  MOV_CH_LAYOUT_HEXAGONAL = (110 << 16) | 6,
63  MOV_CH_LAYOUT_OCTAGONAL = (111 << 16) | 8,
64  MOV_CH_LAYOUT_CUBE = (112 << 16) | 8,
65  MOV_CH_LAYOUT_MPEG_3_0_A = (113 << 16) | 3,
66  MOV_CH_LAYOUT_MPEG_3_0_B = (114 << 16) | 3,
67  MOV_CH_LAYOUT_MPEG_4_0_A = (115 << 16) | 4,
68  MOV_CH_LAYOUT_MPEG_4_0_B = (116 << 16) | 4,
69  MOV_CH_LAYOUT_MPEG_5_0_A = (117 << 16) | 5,
70  MOV_CH_LAYOUT_MPEG_5_0_B = (118 << 16) | 5,
71  MOV_CH_LAYOUT_MPEG_5_0_C = (119 << 16) | 5,
72  MOV_CH_LAYOUT_MPEG_5_0_D = (120 << 16) | 5,
73  MOV_CH_LAYOUT_MPEG_5_1_A = (121 << 16) | 6,
74  MOV_CH_LAYOUT_MPEG_5_1_B = (122 << 16) | 6,
75  MOV_CH_LAYOUT_MPEG_5_1_C = (123 << 16) | 6,
76  MOV_CH_LAYOUT_MPEG_5_1_D = (124 << 16) | 6,
77  MOV_CH_LAYOUT_MPEG_6_1_A = (125 << 16) | 7,
78  MOV_CH_LAYOUT_MPEG_7_1_A = (126 << 16) | 8,
79  MOV_CH_LAYOUT_MPEG_7_1_B = (127 << 16) | 8,
80  MOV_CH_LAYOUT_MPEG_7_1_C = (128 << 16) | 8,
82  MOV_CH_LAYOUT_SMPTE_DTV = (130 << 16) | 8,
83  MOV_CH_LAYOUT_ITU_2_1 = (131 << 16) | 3,
84  MOV_CH_LAYOUT_ITU_2_2 = (132 << 16) | 4,
85  MOV_CH_LAYOUT_DVD_4 = (133 << 16) | 3,
86  MOV_CH_LAYOUT_DVD_5 = (134 << 16) | 4,
87  MOV_CH_LAYOUT_DVD_6 = (135 << 16) | 5,
88  MOV_CH_LAYOUT_DVD_10 = (136 << 16) | 4,
89  MOV_CH_LAYOUT_DVD_11 = (137 << 16) | 5,
90  MOV_CH_LAYOUT_DVD_18 = (138 << 16) | 5,
91  MOV_CH_LAYOUT_AUDIOUNIT_6_0 = (139 << 16) | 6,
92  MOV_CH_LAYOUT_AUDIOUNIT_7_0 = (140 << 16) | 7,
94  MOV_CH_LAYOUT_AAC_6_0 = (141 << 16) | 6,
95  MOV_CH_LAYOUT_AAC_6_1 = (142 << 16) | 7,
96  MOV_CH_LAYOUT_AAC_7_0 = (143 << 16) | 7,
97  MOV_CH_LAYOUT_AAC_OCTAGONAL = (144 << 16) | 8,
98  MOV_CH_LAYOUT_TMH_10_2_STD = (145 << 16) | 16,
99  MOV_CH_LAYOUT_TMH_10_2_FULL = (146 << 16) | 21,
100  MOV_CH_LAYOUT_AC3_1_0_1 = (149 << 16) | 2,
101  MOV_CH_LAYOUT_AC3_3_0 = (150 << 16) | 3,
102  MOV_CH_LAYOUT_AC3_3_1 = (151 << 16) | 4,
103  MOV_CH_LAYOUT_AC3_3_0_1 = (152 << 16) | 4,
104  MOV_CH_LAYOUT_AC3_2_1_1 = (153 << 16) | 4,
105  MOV_CH_LAYOUT_AC3_3_1_1 = (154 << 16) | 5,
106  MOV_CH_LAYOUT_EAC3_6_0_A = (155 << 16) | 6,
107  MOV_CH_LAYOUT_EAC3_7_0_A = (156 << 16) | 7,
108  MOV_CH_LAYOUT_EAC3_6_1_A = (157 << 16) | 7,
109  MOV_CH_LAYOUT_EAC3_6_1_B = (158 << 16) | 7,
110  MOV_CH_LAYOUT_EAC3_6_1_C = (159 << 16) | 7,
111  MOV_CH_LAYOUT_EAC3_7_1_A = (160 << 16) | 8,
112  MOV_CH_LAYOUT_EAC3_7_1_B = (161 << 16) | 8,
113  MOV_CH_LAYOUT_EAC3_7_1_C = (162 << 16) | 8,
114  MOV_CH_LAYOUT_EAC3_7_1_D = (163 << 16) | 8,
115  MOV_CH_LAYOUT_EAC3_7_1_E = (164 << 16) | 8,
116  MOV_CH_LAYOUT_EAC3_7_1_F = (165 << 16) | 8,
117  MOV_CH_LAYOUT_EAC3_7_1_G = (166 << 16) | 8,
118  MOV_CH_LAYOUT_EAC3_7_1_H = (167 << 16) | 8,
119  MOV_CH_LAYOUT_DTS_3_1 = (168 << 16) | 4,
120  MOV_CH_LAYOUT_DTS_4_1 = (169 << 16) | 5,
121  MOV_CH_LAYOUT_DTS_6_0_A = (170 << 16) | 6,
122  MOV_CH_LAYOUT_DTS_6_0_B = (171 << 16) | 6,
123  MOV_CH_LAYOUT_DTS_6_0_C = (172 << 16) | 6,
124  MOV_CH_LAYOUT_DTS_6_1_A = (173 << 16) | 7,
125  MOV_CH_LAYOUT_DTS_6_1_B = (174 << 16) | 7,
126  MOV_CH_LAYOUT_DTS_6_1_C = (175 << 16) | 7,
127  MOV_CH_LAYOUT_DTS_6_1_D = (182 << 16) | 7,
128  MOV_CH_LAYOUT_DTS_7_0 = (176 << 16) | 7,
129  MOV_CH_LAYOUT_DTS_7_1 = (177 << 16) | 8,
130  MOV_CH_LAYOUT_DTS_8_0_A = (178 << 16) | 8,
131  MOV_CH_LAYOUT_DTS_8_0_B = (179 << 16) | 8,
132  MOV_CH_LAYOUT_DTS_8_1_A = (180 << 16) | 9,
133  MOV_CH_LAYOUT_DTS_8_1_B = (181 << 16) | 9,
134 };
135 
137  uint32_t tag;
138  uint64_t layout;
139 };
140 
145  { MOV_CH_LAYOUT_UNKNOWN, 0 },
146  { MOV_CH_LAYOUT_TMH_10_2_STD, 0 }, // L, R, C, Vhc, Lsd, Rsd,
147  // Ls, Rs, Vhl, Vhr, Lw, Rw,
148  // Csd, Cs, LFE1, LFE2
149  { MOV_CH_LAYOUT_TMH_10_2_FULL, 0 }, // L, R, C, Vhc, Lsd, Rsd,
150  // Ls, Rs, Vhl, Vhr, Lw, Rw,
151  // Csd, Cs, LFE1, LFE2, Lc, Rc,
152  // HI, VI, Haptic
153  { 0, 0 },
154 };
155 
158 };
159 
165  { MOV_CH_LAYOUT_XY, AV_CH_LAYOUT_STEREO }, // X (left), Y (right)
166 
168 
171  { 0, 0 },
172 };
173 
178 
179  { MOV_CH_LAYOUT_ITU_2_1, AV_CH_LAYOUT_2_1 }, // L, R, Cs
180 
181  { MOV_CH_LAYOUT_DVD_4, AV_CH_LAYOUT_2POINT1 }, // L, R, LFE
182  { 0, 0 },
183 };
184 
186  { MOV_CH_LAYOUT_AMBISONIC_B_FORMAT, 0 }, // W, X, Y, Z
187 
188  { MOV_CH_LAYOUT_QUADRAPHONIC, AV_CH_LAYOUT_QUAD }, // L, R, Rls, Rrs
189 
192  { MOV_CH_LAYOUT_AC3_3_1, AV_CH_LAYOUT_4POINT0 }, // L, C, R, Cs
193 
194  { MOV_CH_LAYOUT_ITU_2_2, AV_CH_LAYOUT_2_2 }, // L, R, Ls, Rs
195 
196  { MOV_CH_LAYOUT_DVD_5, AV_CH_LAYOUT_2_1 | // L, R, LFE, Cs
198  { MOV_CH_LAYOUT_AC3_2_1_1, AV_CH_LAYOUT_2_1 | // L, R, Cs, LFE
200 
201  { MOV_CH_LAYOUT_DVD_10, AV_CH_LAYOUT_3POINT1 }, // L, R, C, LFE
202  { MOV_CH_LAYOUT_AC3_3_0_1, AV_CH_LAYOUT_3POINT1 }, // L, C, R, LFE
203  { MOV_CH_LAYOUT_DTS_3_1, AV_CH_LAYOUT_3POINT1 }, // C, L, R, LFE
204  { 0, 0 },
205 };
206 
208  { MOV_CH_LAYOUT_PENTAGONAL, AV_CH_LAYOUT_5POINT0_BACK }, // L, R, Rls, Rrs, C
209 
210  { MOV_CH_LAYOUT_MPEG_5_0_A, AV_CH_LAYOUT_5POINT0 }, // L, R, C, Ls, Rs
211  { MOV_CH_LAYOUT_MPEG_5_0_B, AV_CH_LAYOUT_5POINT0 }, // L, R, Ls, Rs, C
212  { MOV_CH_LAYOUT_MPEG_5_0_C, AV_CH_LAYOUT_5POINT0 }, // L, C, R, Ls, Rs
213  { MOV_CH_LAYOUT_MPEG_5_0_D, AV_CH_LAYOUT_5POINT0 }, // C, L, R, Ls, Rs
214 
215  { MOV_CH_LAYOUT_DVD_6, AV_CH_LAYOUT_2_2 | // L, R, LFE, Ls, Rs
217  { MOV_CH_LAYOUT_DVD_18, AV_CH_LAYOUT_2_2 | // L, R, Ls, Rs, LFE
219 
220  { MOV_CH_LAYOUT_DVD_11, AV_CH_LAYOUT_4POINT1 }, // L, R, C, LFE, Cs
221  { MOV_CH_LAYOUT_AC3_3_1_1, AV_CH_LAYOUT_4POINT1 }, // L, C, R, Cs, LFE
222  { MOV_CH_LAYOUT_DTS_4_1, AV_CH_LAYOUT_4POINT1 }, // C, L, R, Cs, LFE
223  { 0, 0 },
224 };
225 
227  { MOV_CH_LAYOUT_HEXAGONAL, AV_CH_LAYOUT_HEXAGONAL }, // L, R, Rls, Rrs, C, Cs
228  { MOV_CH_LAYOUT_DTS_6_0_C, AV_CH_LAYOUT_HEXAGONAL }, // C, Cs, L, R, Rls, Rrs
229 
230  { MOV_CH_LAYOUT_MPEG_5_1_A, AV_CH_LAYOUT_5POINT1 }, // L, R, C, LFE, Ls, Rs
231  { MOV_CH_LAYOUT_MPEG_5_1_B, AV_CH_LAYOUT_5POINT1 }, // L, R, Ls, Rs, C, LFE
232  { MOV_CH_LAYOUT_MPEG_5_1_C, AV_CH_LAYOUT_5POINT1 }, // L, C, R, Ls, Rs, LFE
233  { MOV_CH_LAYOUT_MPEG_5_1_D, AV_CH_LAYOUT_5POINT1 }, // C, L, R, Ls, Rs, LFE
234 
235  { MOV_CH_LAYOUT_AUDIOUNIT_6_0, AV_CH_LAYOUT_6POINT0 }, // L, R, Ls, Rs, C, Cs
236  { MOV_CH_LAYOUT_AAC_6_0, AV_CH_LAYOUT_6POINT0 }, // C, L, R, Ls, Rs, Cs
237  { MOV_CH_LAYOUT_EAC3_6_0_A, AV_CH_LAYOUT_6POINT0 }, // L, C, R, Ls, Rs, Cs
238 
239  { MOV_CH_LAYOUT_DTS_6_0_A, AV_CH_LAYOUT_6POINT0_FRONT }, // Lc, Rc, L, R, Ls, Rs
240 
241  { MOV_CH_LAYOUT_DTS_6_0_B, AV_CH_LAYOUT_5POINT0_BACK | // C, L, R, Rls, Rrs, Ts
243  { 0, 0 },
244 };
245 
247  { MOV_CH_LAYOUT_MPEG_6_1_A, AV_CH_LAYOUT_6POINT1 }, // L, R, C, LFE, Ls, Rs, Cs
248  { MOV_CH_LAYOUT_AAC_6_1, AV_CH_LAYOUT_6POINT1 }, // C, L, R, Ls, Rs, Cs, LFE
249  { MOV_CH_LAYOUT_EAC3_6_1_A, AV_CH_LAYOUT_6POINT1 }, // L, C, R, Ls, Rs, LFE, Cs
250  { MOV_CH_LAYOUT_DTS_6_1_D, AV_CH_LAYOUT_6POINT1 }, // C, L, R, Ls, Rs, LFE, Cs
251 
252  { MOV_CH_LAYOUT_AUDIOUNIT_7_0, AV_CH_LAYOUT_7POINT0 }, // L, R, Ls, Rs, C, Rls, Rrs
253  { MOV_CH_LAYOUT_AAC_7_0, AV_CH_LAYOUT_7POINT0 }, // C, L, R, Ls, Rs, Rls, Rrs
254  { MOV_CH_LAYOUT_EAC3_7_0_A, AV_CH_LAYOUT_7POINT0 }, // L, C, R, Ls, Rs, Rls, Rrs
255 
256  { MOV_CH_LAYOUT_AUDIOUNIT_7_0_FRONT, AV_CH_LAYOUT_7POINT0_FRONT }, // L, R, Ls, Rs, C, Lc, Rc
257  { MOV_CH_LAYOUT_DTS_7_0, AV_CH_LAYOUT_7POINT0_FRONT }, // Lc, C, Rc, L, R, Ls, Rs
258 
259  { MOV_CH_LAYOUT_EAC3_6_1_B, AV_CH_LAYOUT_5POINT1 | // L, C, R, Ls, Rs, LFE, Ts
261 
262  { MOV_CH_LAYOUT_EAC3_6_1_C, AV_CH_LAYOUT_5POINT1 | // L, C, R, Ls, Rs, LFE, Vhc
264 
265  { MOV_CH_LAYOUT_DTS_6_1_A, AV_CH_LAYOUT_6POINT1_FRONT }, // Lc, Rc, L, R, Ls, Rs, LFE
266 
267  { MOV_CH_LAYOUT_DTS_6_1_B, AV_CH_LAYOUT_5POINT1_BACK | // C, L, R, Rls, Rrs, Ts, LFE
269 
270  { MOV_CH_LAYOUT_DTS_6_1_C, AV_CH_LAYOUT_6POINT1_BACK }, // C, Cs, L, R, Rls, Rrs, LFE
271  { 0, 0 },
272 };
273 
275  { MOV_CH_LAYOUT_OCTAGONAL, AV_CH_LAYOUT_OCTAGONAL }, // L, R, Rls, Rrs, C, Cs, Ls, Rs
276  { MOV_CH_LAYOUT_AAC_OCTAGONAL, AV_CH_LAYOUT_OCTAGONAL }, // C, L, R, Ls, Rs, Rls, Rrs, Cs
277 
278  { MOV_CH_LAYOUT_CUBE, AV_CH_LAYOUT_QUAD | // L, R, Rls, Rrs, Vhl, Vhr, Rlt, Rrt
283 
284  { MOV_CH_LAYOUT_MPEG_7_1_A, AV_CH_LAYOUT_7POINT1_WIDE }, // L, R, C, LFE, Ls, Rs, Lc, Rc
285  { MOV_CH_LAYOUT_MPEG_7_1_B, AV_CH_LAYOUT_7POINT1_WIDE }, // C, Lc, Rc, L, R, Ls, Rs, LFE
286  { MOV_CH_LAYOUT_EMAGIC_DEFAULT_7_1, AV_CH_LAYOUT_7POINT1_WIDE }, // L, R, Ls, Rs, C, LFE, Lc, Rc
287  { MOV_CH_LAYOUT_EAC3_7_1_B, AV_CH_LAYOUT_7POINT1_WIDE }, // L, C, R, Ls, Rs, LFE, Lc, Rc
288  { MOV_CH_LAYOUT_DTS_7_1, AV_CH_LAYOUT_7POINT1_WIDE }, // Lc, C, Rc, L, R, Ls, Rs, LFE
289 
290  { MOV_CH_LAYOUT_MPEG_7_1_C, AV_CH_LAYOUT_7POINT1 }, // L, R, C, LFE, Ls, Rs, Rls, Rrs
291  { MOV_CH_LAYOUT_EAC3_7_1_A, AV_CH_LAYOUT_7POINT1 }, // L, C, R, Ls, Rs, LFE, Rls, Rrs
292 
293  { MOV_CH_LAYOUT_SMPTE_DTV, AV_CH_LAYOUT_5POINT1 | // L, R, C, LFE, Ls, Rs, Lt, Rt
295 
296  { MOV_CH_LAYOUT_EAC3_7_1_C, AV_CH_LAYOUT_5POINT1 | // L, C, R, Ls, Rs, LFE, Lsd, Rsd
299 
300  { MOV_CH_LAYOUT_EAC3_7_1_D, AV_CH_LAYOUT_5POINT1 | // L, C, R, Ls, Rs, LFE, Lw, Rw
303 
304  { MOV_CH_LAYOUT_EAC3_7_1_E, AV_CH_LAYOUT_5POINT1 | // L, C, R, Ls, Rs, LFE, Vhl, Vhr
307 
308  { MOV_CH_LAYOUT_EAC3_7_1_F, AV_CH_LAYOUT_5POINT1 | // L, C, R, Ls, Rs, LFE, Cs, Ts
311 
312  { MOV_CH_LAYOUT_EAC3_7_1_G, AV_CH_LAYOUT_5POINT1 | // L, C, R, Ls, Rs, LFE, Cs, Vhc
315 
316  { MOV_CH_LAYOUT_EAC3_7_1_H, AV_CH_LAYOUT_5POINT1 | // L, C, R, Ls, Rs, LFE, Ts, Vhc
319 
320  { MOV_CH_LAYOUT_DTS_8_0_A, AV_CH_LAYOUT_2_2 | // Lc, Rc, L, R, Ls, Rs, Rls, Rrs
325 
326  { MOV_CH_LAYOUT_DTS_8_0_B, AV_CH_LAYOUT_5POINT0 | // Lc, C, Rc, L, R, Ls, Cs, Rs
330  { 0, 0 },
331 };
332 
334  { MOV_CH_LAYOUT_DTS_8_1_A, AV_CH_LAYOUT_2_2 | // Lc, Rc, L, R, Ls, Rs, Rls, Rrs, LFE
340 
341  { MOV_CH_LAYOUT_DTS_8_1_B, AV_CH_LAYOUT_7POINT1_WIDE | // Lc, C, Rc, L, R, Ls, Cs, Rs, LFE
343  { 0, 0 },
344 };
345 
346 static const struct MovChannelLayoutMap *mov_ch_layout_map[] = {
357 };
358 
383  0,
384 };
385 
401  0,
402 };
403 
413  0,
414 };
415 
416 static const struct {
419 } mov_codec_ch_layouts[] = {
420  { CODEC_ID_AAC, mov_ch_layouts_aac },
421  { CODEC_ID_AC3, mov_ch_layouts_ac3 },
422  { CODEC_ID_ALAC, mov_ch_layouts_alac },
423  { CODEC_ID_NONE, NULL },
424 };
425 
426 uint64_t ff_mov_get_channel_layout(uint32_t tag, uint32_t bitmap)
427 {
428  int i, channels;
429  const struct MovChannelLayoutMap *layout_map;
430 
431  /* use ff_mov_get_channel_label() to build a layout instead */
433  return 0;
434 
435  /* handle the use of the channel bitmap */
436  if (tag == MOV_CH_LAYOUT_USE_BITMAP)
437  return bitmap < 0x40000 ? bitmap : 0;
438 
439  /* get the layout map based on the channel count for the specified layout tag */
440  channels = tag & 0xFFFF;
441  if (channels > 9)
442  channels = 0;
443  layout_map = mov_ch_layout_map[channels];
444 
445  /* find the channel layout for the specified layout tag */
446  for (i = 0; layout_map[i].tag != 0; i++) {
447  if (layout_map[i].tag == tag)
448  break;
449  }
450  return layout_map[i].layout;
451 }
452 
453 uint32_t ff_mov_get_channel_label(uint32_t label)
454 {
455  if (label == 0)
456  return 0;
457  if (label <= 18)
458  return 1U << (label - 1);
459  if (label == 38)
460  return AV_CH_STEREO_LEFT;
461  if (label == 39)
462  return AV_CH_STEREO_RIGHT;
463  return 0;
464 }
465 
467  uint64_t channel_layout,
468  uint32_t *bitmap)
469 {
470  int i, j;
471  uint32_t tag = 0;
472  const enum MovChannelLayoutTag *layouts = NULL;
473 
474  /* find the layout list for the specified codec */
475  for (i = 0; mov_codec_ch_layouts[i].codec_id != CODEC_ID_NONE; i++) {
476  if (mov_codec_ch_layouts[i].codec_id == codec_id)
477  break;
478  }
479  if (mov_codec_ch_layouts[i].codec_id != CODEC_ID_NONE)
480  layouts = mov_codec_ch_layouts[i].layouts;
481 
482  if (layouts) {
483  int channels;
484  const struct MovChannelLayoutMap *layout_map;
485 
486  /* get the layout map based on the channel count */
487  channels = av_get_channel_layout_nb_channels(channel_layout);
488  if (channels > 9)
489  channels = 0;
490  layout_map = mov_ch_layout_map[channels];
491 
492  /* find the layout tag for the specified channel layout */
493  for (i = 0; layouts[i] != 0; i++) {
494  if (layouts[i] & 0xFFFF != channels)
495  continue;
496  for (j = 0; layout_map[j].tag != 0; j++) {
497  if (layout_map[j].tag == layouts[i] &&
498  layout_map[j].layout == channel_layout)
499  break;
500  }
501  if (layout_map[j].tag)
502  break;
503  }
504  tag = layouts[i];
505  }
506 
507  /* if no tag was found, use channel bitmap as a backup if possible */
508  if (tag == 0 && channel_layout > 0 && channel_layout < 0x40000) {
510  *bitmap = (uint32_t)channel_layout;
511  } else
512  *bitmap = 0;
513 
514  /* TODO: set channel descriptions as a secondary backup */
515 
516  return tag;
517 }