When recordings exist but have no sound: what to check

The recording is there. It has a filename, a sensible file size, and it shows up in the recording log. But when you play it, you hear silence, or only one side of the conversation, or a faint hiss. This is a different problem from missing recordings entirely. The file got created, which means the recorder fired — so the question is why no usable audio made it into the file. That points straight at the media path and the way the two call legs get mixed together.

How a recording is actually built

Call recording in VICIdial works by capturing the RTP audio streams of the call — the live packets of voice flowing in each direction — and mixing them into a single file when the call ends. There are two legs: the customer's audio and the agent's audio. The recorder grabs both, then muxes them together. If one leg never delivered audio to the box, that side of the recording is silent even though the file itself is perfectly valid.

One side silent versus both sides silent

Split the symptom first. If you can hear the agent but not the customer (or vice versa), one RTP stream never reached the box — the same root cause as One-way audio on a live call, usually a routing or NAT issue on one leg. If both sides are silent, suspect the mix or the format instead: the recorder ran but had nothing usable to write, or the file was encoded in a way your player cannot decode.

Format and codec

The Recording format (WAV/MP3) decides the container and encoding written to disk — commonly a compressed format to save space or an uncompressed one for fidelity. A file that opens but stays silent can simply be in a format your player does not handle, so test with a different player before assuming the audio is gone. The Codec in use on the call matters too: an unexpected transcode or a codec the recorder cannot capture cleanly can leave you with a valid-looking but empty file.

The recording delay

There is a Recording delay between when a call connects and when capture actually begins. If that delay is set too high, the opening of every call is missing, and on short calls the entire conversation can fall inside the delay window — giving you a file with almost no audio in it. If your silent recordings are all short calls, check this value first.

Walking the checks

flowchart TD
  A[Recording exists but is silent] --> B{One side or both}
  B -->|One side| C[Missing RTP on one leg same as one way audio]
  B -->|Both| D{Plays in another player}
  D -->|Yes| E[Was a format or codec issue]
  D -->|No| F{Call shorter than recording delay}
  F -->|Yes| G[Lower the recording delay]
  F -->|No| H[Check mux and codec on the box]

If you record two-channel files, a Stereo recording puts each leg on its own channel, which makes a one-sided recording obvious the instant you open it — one channel has a waveform and the other is flat. That alone can tell you which leg lost its audio.

Where to go next

If recordings are not appearing at all rather than playing silent, that is a separate path covered in fixing missing recordings. For the full first-response checklist, see the VICIdial troubleshooting playbook.

If you would rather not babysit recording paths and storage, VICIfast runs a hardened, managed VICIdial box that is live in under 40 seconds. See our plans and pricing.