Ask Your Question

Revision history [back]

Isochronous audio data missing

I'm recording audio from a microphone and I noticed that sometimes ISO packets don't have any data in them during active recording. Recordings work perfectly fine on a Windows PC but have issues on Mac, such as audio drops, repeats etc.

Usually I'd see something like this while I'm recording in the USB isochronous packet:

ISO Data offset: xxxx

ISO Data length: 0x00000020 (relevant) //Max packet size is 32 Bytes

ISO USBD status: xxxx

ISO Data: Hex Data

But sometimes in between Hex Data packets, I'd see empty packets with no data at all, not even 0s.

ISO Data offset: xxxx

ISO Data length: 0x00000000 (relevant)

ISO USBD status: xxxx

ISO Data field is missing

My guess is that these missing data packets are responsible for the behavior on Mac. Are these packets considered Zero Length Packets telling host transmission is over? Even though more data is still coming in?