Opus Recommended Settings
Depending on what kinds of sounds you want to encode with Opus, you'll want different settings.
The following table has rough guidelines to help you get your required quality, file size or latency. The table is originally taken from the HydrogenAudio wiki, which has some great information on Opus and its usage.
| Bitrate target | Stereo mode | Bandwidth | typ SILK/CELT use | Music quality notes | Use cases/notes/competitive codecs |
|---|---|---|---|---|---|
| 6 kbps | mono | 4 kHz | SILK | Poor, muffled sound but intelligible lyrics. | - |
| 8 kbps | mono | 4 kHz | SILK | Poor, muffled but OK for bitrate | - |
| 14 to 16 kbps | mono | 6 kHz | SILK | Fairly Poor but OK for bitrate | Perhaps acceptable for incidental music |
| 22 to 24 kbps | mono | 8 kHz | SILK | Fair but OK for bitrate | OK for incidental music |
| 32 kbps | mono | 12 kHz | hybrid | Moderately good mono, reasonably bright treble (c.f. mono cassette) | Good for podcasts, audiobooks, CELT-only poss for music. Competitor HE-AAC@32kbps is stereo full-band but with annoying artifacts. |
| 36 to 40 kbps | stereo | 12 kHz | hybrid/CELT | Moderately good stereo, reasonably bright treble (c.f. stereo cassette) | Stereo podcasts, audiobooks, very low bitrate music |
| 48 kbps | stereo | 20 kHz | CELT | Full bandwidth stereo music, some artifacts, rarely nasty | Stereo podcasts, audiobooks, low bitrate music |
| 64 kbps | stereo | 20 kHz | CELT | Full bandwidth stereo music, nice sound, detectable differences to original (mostly 'not annoying') | Music storage & streaming. Beat HE-AAC, Vorbis, MP3 in listening test |
| 96 kbps | stereo | 20 kHz | CELT | Full bandwidth stereo music, good quality approaching transparency | Music storage & high quality streaming. Beat LC-AAC, Vorbis, MP3 in listening test |
| 112 kbps | stereo | 20 kHz | CELT | Fairly close to transparency (needs more testing) | Music storage & high quality streaming. Very low-latency stereo networked music performance/jam sessions at OK quality (see below table) |
| 128 kbps | stereo | 20 kHz | CELT | Very close to transparency (needs more testing). Most modern codecs competitive (AAC-LC, Vorbis, MP3) | Music storage & streaming. Future download music sales. |
| 256 kbps | stereo | 20 kHz | CELT | Transparent with very low chance of artifacts (a few killer samples still detectable). Most old & new lossy codecs competitive. | Music storage & streaming, dedicated limited-bandwidth audio links (e.g. wireless, A2DP-bluetooth type links). |
| 510 kbps | stereo | 20 kHz | CELT | Maximum possible stereo bitrate target (actual rate often less than 510 for default frame size). Most old and new lossy codecs competitive, plus near-lossless lossyWAV and WavPack lossy | Music storage, dedicated limited-bitrate audio links (e.g. wireless, minimum latency high quality audio. LossyWAV and WavPack lossy are very competitive for storage, and WavPack lossy --blocksize=256 may be competitive with minimum latency mode also. |
| >510 kbps | - | - | - | Above Opus bitrate range allowed for stereo sources | Settle for 510kbps or use lossless, lossyWAV, WavPack lossy or lossy transform/subband codecs like Vorbis, Musepack at very high settings. |
Bandwidth Transition Thresholds
The following table was copied from the opus_encoder.c source file.
| (bitrates in KHz) | Mono | Stereo | ||
|---|---|---|---|---|
| Voice | Music | Voice | Music | |
| NB ↔ MB | 11 ± 1 | 12 ± 1 | 11 ± 1 | 12 ± 2 |
| MB ↔ WB | 14 ± 1 | 15 ± 1 | 14 ± 2 | 18 ± 2 |
| WB ↔ SWB | 17 ± 1 | 18 ± 1 | 21 ± 2 | 21 ± 2 |
| SWB ↔ FB | 21 ± 1 | 22 ± 2 | 28 ± 2 | 30 ± 2 |