| Codec | Rate (kHz) | bitrate (kbps) | frame size (ms) | total delay (ms) | Robustness | license |
|---|---|---|---|---|---|---|
| CELT | 32-96 |
24-128 (mono) 40-160 (stereo) |
<5.8 (44.1 kHz) <5.3 (48 kHz) |
<8.7 (44.1 kHz) <8.0 (48 kHz) |
packet loss, bit errors | open-source/ free software |
| G.722.1C (Siren14) | 32 | 24, 32, 48 | 20 | 40 | packet loss, bit errors | no charge, but not open-source |
| AAC-LD | 16-48 | 16-128 | from 10 to 11.6 | from 20 to 50+ | packet loss | proprietary, MPEG |
| Fraunhofer ULD | 32-48 | 48-192? | <10 | <10 | limited | proprietary, non-standard |
These are the results of MUSHRA tests comparing CELT with AAC-LD, G.722.1C and MP3, with 10 listeners. We used version 0.3.2 of the CELT codec with 5.8 ms frames (256 samples) and 2.9 ms (128 samples) look-ahead, for a total of 8.7 ms at 44.1 kHz. As for AAC-LD, we used Apple's implementation, which has 11.6 ms frames and 23.2 ms look-ahead, for a total of 34.8 ms delay at 44.1 kHz. The MP3 implementation is LAME in CBR more and is only included for reference purposes only.
The first graph is for the 48 kbit/s listening test.
The second graph is for the 64 kbit/s listening test. Note that G.722.1C is still at 48 kbit/s in that test because it is the highest bit-rate it supports.
