Chronicall supports all Cisco supported voice codecs (G.711, G.722, G.729) except iLBC and iSAC.
However, when Cisco RTP-forking based central recording is used UCM and the phones might drop call recording sessions, and even calls if transcoding is not properly configured.
- Recorder and recorded phone are on different sites, WAN link bandwidth limitation requires low bitrate voice codec
- Recorder and recorded phones are in different UCM regions
- Codec change in a consultative transfer or joining a conference
Recorder and recorded phone are on different sites.
- WAN link bandwidth limitation requires low bitrate voice codec
- In this case, it is recommended to put the recorder into different UCM region, and set inter-region codec according to available bandwidth.
- Example: Phones at remote branch office are using the G.722/G.711 codec for internal calls. Between recorder and remote office G.729 codec would be preferred due to the office's upload bandwidth limitations.
Different UCM regions
Recorder and recorded phones are in different UCM Regions.
- If the intra region codec bitrate (codec used in the "original" calls between phones/gateways in the same region) is higher than inter-region codec between recorder and phone, then UCM is forced to insert a transcoder at the phone region to transcode the voice sent to the recorder, in order to match the inter-region codec bitrate.
- Example: original call bitrate is 64 kbps (G.711 or G.722), recorder - phone region relationship dictates 8 kbps G.729 (default inter-region codec in UCM).
Codec change in a consultative transfer or joining a conference
- If a different codec is involved in the consultation call leg, and after transfer/in conference leg UCM drops both the recording and original call session.
- This is a known Cisco issue, consultation and after consultation legs are recorded in the same session (from transferee or conferee point of view) when the phone starts a recording session using a certain codec, it gets "locked" into that codec. Verba supports mid-call codec change, but UCM does not support this in case of recorder calls. A transcoder can handle this situation, and UCM tries to insert it into the call to do transcoding between new call leg's codec and the "locked" codec.
- Example: Consultative transfer, Agent A calls recorded Agent B to transfer Customer C calling from PSTN. A->B internal call leg use G.722 codec, after transfer C->B gateway call leg switches to G.711. These call legs from B's point of view are handled in the same recording session by UCM, and due to locking the Built-in Bridge to G.722 causes to drop the second call leg.