Isochronous Transfers are used for transmitting real-time information such as audio and video data, and must be sent at a constant rate. USB isochronous data streams are allocated a dedicated portion of USB bandwidth to ensure that data can be delivered at the desired rate. An Isochronous pipe sends a new data packet in every frame, regardless of the success or failure of the last packet.

The maximum packet size for the isochronous endpoint data is:

1023 or less bytes for full-speed
1024 or less bytes for high-speed

Isochronous Transfers have no error detection. Any error in electrical transmission is not corrected.

Isochronous Transfers are also subject to timing jitters as described for Interrupt Transfers.

Isochronous Transfer Format