Ultra-low latency audio over bluetooth

Patent metadata

Field	Value
Publication number	US-2019104424-A1
Application number	US-201816146571-A
Country	US
Kind code	A1
Filing date	Sep 28, 2018
Priority date	Sep 29, 2017
Publication date	Apr 4, 2019
Grant date	—

Abstract

Methods and apparatus for communicating audio packets with ultra-low latency at high data rates from an audio source device to one or more audio output devices over a wireless personal area network (WPAN) connection, such as via a Bluetooth connection. Latency is reduced by using time-efficient audio coding and decoding, limited retransmissions, reduced time and frequency of acknowledgements, and by combining Bluetooth Classic (BTC) packets for downlink audio and downlink control with Bluetooth Low Energy (BTLE) packets for uplink control, uplink acknowledgements, and inter-device wireless communication. The number of retransmissions and packet concealments per frame cycle can be limited to an upper threshold number to satisfy a low latency requirement.

First claim

What is claimed is:

1 . A method for low latency communication between an audio source device and a primary audio output device, the method comprising:
by the audio source device:
sending, to the primary audio output device during a first portion of a frame, a forward audio packet that includes audio data and is formatted in accordance with a Bluetooth (BT) Classic wireless communication protocol or a high data rate (HDR) extension thereof;
receiving, from the primary audio output device during a second portion of the frame, a first reverse acknowledgement (ACK) packet that indicates a request for retransmission of the audio data and is formatted in accordance with a Bluetooth Low Energy (BTLE) wireless communication protocol or an extension thereof;
sending, to the primary audio output device, a second forward audio packet in a first portion of a subsequent frame that immediately follows the frame, the second forward audio packet including retransmission of the audio data; and
disallowing retransmission of audio data for all subsequent frames of a frame cycle that includes the frame and the subsequent frame.

2 . The method of claim 1 , further comprising:
by the audio source device:
receiving, during a final frame of the frame cycle from the primary audio output device, a second reverse ACK packet that includes information derived from inter-device control packets received by the primary audio output device from a secondary audio output device that is connected to the primary audio output device.

3 . The method of claim 2 , wherein:
the primary audio output device and the secondary audio output device are connected to each other wirelessly; and the second reverse ACK packet further comprises a block acknowledgement for a set of two or more forward audio packets.

4 . The method of claim 3 , wherein the second reverse ACK packet further comprises control data from the primary audio output device or the secondary audio output device.

5 . The method of claim 1 , further comprising:
by the audio source device:
receiving during the second portion of the frame, from a secondary audio output device that is wirelessly connected to the primary audio output device, a third reverse ACK packet that indicates a separate request for retransmission of the audio data of the forward audio packet by the secondary audio output device and is formatted in accordance with the Bluetooth Low Energy (BTLE) wireless communication protocol or the extension thereof.

6 . The method of claim 1 , wherein the forward audio packet occupies a time interval less than half of the frame.

7 . The method of claim 6 , wherein the first reverse ACK packet occupies a time interval less than half of a remainder of the frame that is not occupied by the forward audio packet.

8 . The method of claim 7 , wherein the forward audio packet includes at least 300 bytes of uncompressed audio data and up to 50 bytes of control data.

9 . The method of claim 1 , wherein each frame of the frame cycle spans at most 1250 microseconds.

10 . The method of claim 9 , wherein the frame cycle spans at most 20 milliseconds.

11 . An audio source device configurable for low latency communication when paired with a primary audio output device and with a secondary audio output device, the audio source device comprising:
one or more processors communicatively coupled to a memory storing instructions that, when executed by the one or more processors, cause the audio source device to:
send, to the primary audio output device during a first portion of a frame, a forward audio packet that includes audio data and is formatted in accordance with a Bluetooth (BT) Classic wireless communication protocol or a high data rate (HDR) extension thereof;
receive, from the primary audio output device during a second portion of the frame, a first reverse acknowledgement (ACK) packet that indicates a request for retransmission of the audio data and is formatted in accordance with a Bluetooth Low Energy (BTLE) wireless communication protocol or an extension thereof;
send, to the primary audio output device, a second forward audio packet in a first portion of a subsequent frame that immediately follows the frame, the second forward audio packet including retransmission of the audio data; and
disallow retransmission of audio data for all subsequent frames of a frame cycle that includes the frame and the subsequent frame.

12 . The audio source device of claim 11 , wherein execution of the instructions further causes the audio source device to re-allow a request for retransmission of a forward audio packet during a subsequent frame cycle that follows the frame cycle that included the retransmission of the audio data.

13 . The audio source device of claim 11 , wherein execution of the instructions further causes the audio source device to:
receive, during a final frame of the frame cycle from the primary audio output device, a second reverse ACK packet that includes information derived from inter-device control packets received by the primary audio output device from the secondary audio output device.

14 . The audio source device of claim 13 , wherein the second reverse ACK packet further comprises a user command received via an interface of the primary audio output device.

15 . The audio source device of claim 13 , wherein execution of the instructions further causes the audio source device to:
receive during the second portion of the frame, from the secondary audio output device that is wirelessly connected to the primary audio output device, a third reverse ACK packet that indicates a separate request for retransmission of the audio data of the forward audio packet by the secondary audio output device and is formatted in accordance with the Bluetooth Low Energy (BTLE) wireless communication protocol or the extension thereof.

16 . The audio source device of claim 15 , wherein:
the forward audio packet occupies a time interval less than half of the frame; and the first reverse ACK packet and the third reverse ACK packet each occupy a time interval less than half of a remainder of the frame that is not occupied by the forward audio packet.

17 . The audio source device of claim 11 , wherein the forward audio packet includes at least 300 bytes of uncompressed audio data and up to 50 bytes of control data.

18 . The audio source device of claim 17 , wherein each frame of the frame cycle spans at most 1250 microseconds.

19 . An apparatus configurable for operation in an audio source device, the apparatus comprising a processor communicatively coupled to a memory storing instructions that, when executed by the processor, cause the audio source device to:
send, to a primary audio output device during a first portion of a frame, a forward audio packet that includes audio data and is formatted in accordance with a Bluetooth Classic wireless communication protocol or a high data rate (HDR) extension thereof; receive, from the primary audio output device during a second portion of the frame, a first reverse acknowledgement (ACK) packet that indicates a request for retransmission of the audio data and is formatted in accordance with a Bluetooth Low Energy (BTLE) wireless communication protocol or an extension thereof; send, to the primary audio output device, a second forward audio packet in a first portion of a subsequent frame that immediately follows the frame, the second forward audio packet including retransmission of the audio data; and disallow retransmission of audio

Assignees

• Apple Inc

Inventors

• Hariharan Sriram
• Paycher Alon
• Irony Ran
• Anantharaman Sreeraman
• Silfvast Robert D

Classifications

• H04L1/1621

  Group acknowledgement, i.e. the acknowledgement message defining a range of identifiers, e.g. of sequence numbers · CPC title

• H04L1/1867

  Arrangements specially adapted for the transmitter end · CPC title

• H04R3/12

  for distributing signals to two or more loudspeakers {(specially adapted for hearing aids H04R25/407)} · CPC title

• H04R2420/07

  Applications of wireless loudspeakers or wireless microphones · CPC title

• H04W84/12

  WLAN [Wireless Local Area Networks] · CPC title