Packetizing encoded audio frames into compressed-over-pulse code modulation (PCM) (COP) packets for transmission over PCM interfaces

• US 10,462,269 B2
• Filed: 07/26/2017
• Issued: 10/29/2019
• Est. Priority Date: 08/15/2016
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Bhat Noojady Krishna, Raghavendra, Haverinen, Anssi, Mitnala, Siva Pavan Kumar, Prasad, Jitendra, Timsari, Bijan
• Primary Examiner(s): Moore, Jr., Michael J
• Application Number:
  US15/660,044
• Publication Number:
  US 20180048744A1
• Time in Patent Office: 825 Days
• Field of Search: None
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: H04B 14/04 using pulse code modulation
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC

Abstract

Aspects disclosed in the detailed description include packetizing encoded audio frames into compressed-over-pulse code modulation (PCM) (COP) packets for transmission over PCM interfaces. In one aspect, a COP packetizing circuit is configured to receive an encoded audio frame generated from a PCM frame, and generate a COP packet that includes the encoded audio frame irrespective of the audio format. The COP packet is generated with a packet length proportional to a PCM length of the PCM frame, allowing the COP packetizing circuit to transmit the COP packet over an isochronous PCM interface with a lower bit rate than the PCM frame to reduce power. The COP packetizing circuit provides a mobile computing device with a single packetizing scheme that supports multiple audio formats, and allows for reducing power through bit rate scaling.

Claims

1. A method for packetizing an encoded audio frame based on a pulse code modulation (PCM) frame into a compressed-over-PCM (COP) packet, comprising:

receiving the encoded audio frame generated from the PCM frame having a PCM length;

generating the COP packet having a packet length proportional to the PCM length and comprising;

a COP header comprising data used by a receiver module to depacketize the COP packet, wherein the data comprises a frame intact bit configured to be set to;

a first value in response to detecting that there is no clock skew between the COP packet and the PCM frame, and a second value in response to detecting that there is clock skew between the COP packet and the PCM frame;

a subframe, comprising;

the encoded audio frame; and

a frame length field that indicates a length of the encoded audio frame; and

a zero padding block, comprising;

a zero padding length field that indicates a number of zero bytes in a zero padding field;

the zero padding field comprising the number of zero bytes; and

providing the COP packet to the receiver module over a PCM interface.

2. The method of claim 1, wherein generating the COP packet further comprises generating the COP packet comprising the encoded audio frame in response to the PCM frame having the PCM length with a corresponding real-time audio playback duration of greater than or equal to one (1) millisecond (ms).

3. The method of claim 1, further comprising:

receiving a plurality of encoded audio frames based on a plurality of PCM frames;

wherein generating the COP packet further comprises generating the COP packet comprising the plurality of encoded audio frames in response to each of the plurality of PCM frames having a PCM length with a corresponding real-time audio playback duration of less than one (1) millisecond (ms).

4. The method of claim 1, further comprising increasing the number of zero bytes of the zero padding field in response to the frame intact bit being set to the second value indicating that there is clock skew, wherein a first frequency of a first clock used to record the PCM frame is lower than a second frequency of a second clock used to provide the COP packet over the PCM interface.

5. The method of claim 1, further comprising decreasing the number of zero bytes of the zero padding field in response to the frame intact bit being set to the second value indicating that there is clock skew, wherein a first frequency of a first clock used to record the PCM frame is higher than a second frequency of a second clock used to provide the COP packet over the PCM interface.

6. The method of claim 1, wherein generating the COP packet further comprises generating the COP packet wherein the data further comprises a throughput-feedback field for controlling a bit rate at which a circuit is to provide encoded audio frames encapsulated in feedback-generated COP packets.

7. The method of claim 6, wherein the throughput-feedback field comprises two (2) bits set to indicate that the bit rate equals one of a default rate, a low rate, a medium rate, and a high rate.

8. The method of claim 1, wherein generating the COP packet further comprises generating the COP packet wherein the data further comprises:

a first sync word comprising sixteen (16) bits;

a second sync word comprising 16 bits;

a version field comprising two (2) bits;

an error bit that indicates if errors are present in the COP packet;

an audio format field comprising six (6) bits that indicate an audio format of the encoded audio frame;

a frame storage bit that indicates whether the frame length field represents bits or bytes; and

a subframe number field that indicates a number of subframes included in the COP packet.

13. The method of claim 1, further comprising generating the COP packet with a different sampling rate compared to a sampling rate of the PCM frame to reduce power consumption compared to providing the PCM frame over the PCM interface.

14. The method of claim 6, further comprising:

receiving a feedback-generated COP packet from the circuit;

depacketizing the feedback-generated COP packet into an encoded audio frame; and

providing the encoded audio frame to a corresponding circuit.

15. The method of claim 1, wherein the encoded audio frame may have a Bluetooth™

format selected from the group consisting of;

Low Complexity Subband Coding (SBC), digital audio data reduction technology (aptX), aptX-High Definition (aptX-HD), and advanced audio coding (AAC).

9. A method performed at a circuit comprising a receiver module, comprising:

receiving a compressed-over-pulse code modulation (PCM) (COP) packet having a COP packet length, wherein the COP packet comprises;

a COP header comprising data used by the receiver module to depacketize the COP packet, wherein the data comprises a frame intact bit configured to be set to;

a first value to indicate that there is no clock skew between the COP packet and a PCM frame used to generate an encoded audio frame in the COP packet; and

a second value to indicate that there is clock skew between the COP packet and the PCM frame;

a subframe, comprising;

the encoded audio frame; and

a frame length field that indicates a length of the encoded audio frame; and

a zero padding block, comprising;

a zero padding length field that indicates a number of zero bytes in a zero padding field;

the zero padding field comprising the number of zero bytes;

depacketizing the COP packet into the encoded audio frame; and

providing the encoded audio frame to an audio device configured to use the encoded audio frame for audio playback.

10. The method of claim 9,

further comprising:

responsive to the frame intact bit having the first value, depacketizing the COP packet into the encoded audio frame based on a COP packet length of a previously received COP packet; and

responsive to the frame intact bit having the second value, depacketizing the COP packet into the encoded audio frame based on a clock skew calculated by subtracting the COP packet length of the previously received COP packet from the COP packet length of the COP packet.

11. The method of claim 9, wherein:

the data further comprises a throughput-feedback field for controlling a bit rate at which the circuit is to provide encoded audio frames encapsulated in feedback-generated COP packets;

the method further comprising;

receiving the encoded audio frame generated from the PCM frame having a PCM length;

generating a feedback-generated COP packet comprising the encoded audio frame having the bit rate indicated by the throughput-feedback field; and

providing the feedback-generated COP packet to a corresponding circuit.

12. An audio system, comprising:

a circuit, configured to;

receive a pulse code modulated (PCM) frame having a PCM length;

generate an encoded audio frame from the PCM frame; and

provide the encoded audio frame;

a compressed-over-PCM (COP) packetizing circuit, configured to;

receive the encoded audio frame;

generate a COP packet having a packet length proportional to the PCM length and comprising;

a COP header comprising data used by a receiver module to depacketize the COP packet, wherein the data comprises a frame intact bit configured to be set to;

a first value to indicate that there is no clock skew between the COP packet and the PCM frame used to generate the encoded audio frame in the COP packet; and

a second value to indicate that there is clock skew between the COP packet and the PCM frame;

a subframe, comprising;

the encoded audio frame; and

a frame length field that indicates a length of the encoded audio frame; and

a zero padding block, comprising;

a zero padding length field that indicates a number of zero bytes in a zero padding field;

the zero padding field comprising the number of zero bytes; and

provide the COP packet to the receiver module over a PCM interface;

a circuit comprising the receiver module, configured to;

receive the COP packet;

depacketize the COP packet into the encoded audio frame; and

provide the encoded audio frame to an audio device configured to use the encoded audio frame for audio playback; and

the audio device configured to receive the encoded audio frame.