"error processing ffprobe output: no video track found in file" for audio only input

At the moment, an audio only input will cause a task to fail at the probing step (which currently occurs after Catalyst processing) with:

error processing catalyst callback: error processing ffprobe output: no video track found in file

The following example URLs will trigger the above error for a task:

• ar://VKiPFdMx9yXdaGY8KJDW9U83G1U_zulErRlacgh5AKE
• ar://r-2CB1umeVz4ODjlxJLKAw2DOjGP1h10q4uSGEcIMaY
• ar://QPCRcZRCedI2cM0-j1u1LbWQRdEi2E6fJehZjdQnZa8

All of the above files appear to be ogg files using the opus audio codec for a single audio track.

The error appears to be returned here. The Catalyst MC pipeline seems to be handling the audio only input just fine which is expected since ogg audio only files are in the MC support matrix.

While we could disable the video track check during the probing step, I'm not sure if there are any other things required before we can formally add audio only inputs to our support matrix. So, my suggestion here in the immediate short term is to humanize this error into a invalid video file codec or container... error so that metrics queries/dashboards can filter out errors caused by audio only inputs. Then, separately we can look into formally adding audio only inputs to our support matrix (I suspect we'll want to do this in the near future!) which would allow us to remove the video track check during probing.