num_channels (AC-3) [ATSC Semantics]
num_channels is a 4-bit unsigned integer field in an ATSC AC-3 descriptor that essentially hints at the acmod value in the bsi (bit stream information) stucture of the AC-3 elementary stream being described by the descriptor. See ATSC A/52, Section 5.3.2 for more information.
Values of num_channels above 7 signal the use of surround_mode the low-frequency
effects sub-channel.
valid num_channels values
| num_channels | audio_coding_mode (acmod) |
PMCP numChannelsType |
| 00 / 0x00 | 1 + 1 (Not ATSC) | n/a |
| 01 / 0x01 | 1/0 or 1.0 |
1/0 |
| 02 / 0x02 | 2/0 or 2.0 |
2/0 |
| 03 / 0x03 | 3/0 or 3.0 |
3/0 |
| 04 / 0x04 | 2/1 or 3.0 |
2/1 |
| 05 / 0x05 | 3/1 or 4.0 |
3/1 |
| 06 / 0x06 | 2/2 or 4.0 |
2/2 |
| 07 / 0x07 | 3/2 or 5.0 |
3/2 |
| 08 / 0x08 | 1 |
1 |
| 09 / 0x09 | =<2 or 1.1 |
2_or_less |
| 10 / 0x0A | or=<3or 2.1 |
3_or_less |
| 11 / 0x0B | or=<4 or 3.1 |
4_or_less |
| 12 / 0x0C | or=<5 or 4.1 |
5_or_less |
| 13 / 0x0D | =<6 or 5.1 |
6_or_less |
See: numChannelsType
Reference: ATSC A/52 Table A3.6, ATSC A/53 Section 5.7.3.1
|