Call Recordings

Dual-channel stereo recording with tiered storage and secure playback access.

Every voice call is recorded as a dual-channel stereo file. The caller's audio is captured on one channel; the agent's audio is captured on the other. This separation enables independent analysis of each side - post-call quality scoring can evaluate the agent's delivery separately from the caller's speech.

Recording Format

Channel	Format	Sample Rate	Source
Caller (inbound)	mulaw	8 kHz	Twilio telephony stream
Agent (outbound)	PCM16	16-24 kHz	TTS engine output

The two channels are aligned by a shared timeline marker (media_start_epoch_ms) that enables precise synchronization during playback and analysis.

Storage Lifecycle

Recordings move through three storage tiers based on age:

Tier	Age	Access Time	Use Case
Standard	0-3 days	Immediate	Active review, QA, operator playback
Glacier IR	3+ days	Up to 3 hours to restore	Compliance review, incident investigation
Deep Archive	Long-term	Up to 12 hours to restore	Regulatory retention, legal hold

When you request a recording that has been archived, the system returns a 202 response with an estimated restoration time. Once restored, the recording is available via a presigned URL with a 1-hour expiry.

Access

Recordings are accessed through presigned S3 URLs generated by the Platform API. Each URL is scoped to the requesting workspace and expires after one hour. Metadata includes the call SID, workspace ID, service ID, direction (inbound/outbound), recording format, sample rate, duration, and byte counts.

For how recordings feed into post-call quality scoring, see Audio Pipeline. For how recording data is used in post-call transcript accuracy measurement, see Performance Characteristics.