Using a plurality of buffers to provide audio for synchronized playback to multiple audio devices having separate device clocks

• US 9,176,706 B2
• Filed: 12/01/2014
• Issued: 11/03/2015
• Est. Priority Date: 06/25/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Moore, Jeffrey C., Stewart, William G., Lengeling, Gerhard
• Primary Examiner(s): PEYTON, TAMMARA R
• Application Number:
  US14/557,349
• Publication Number:
  US 20150186104A1
• Time in Patent Office: 337 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/00 Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
• CPC Class Codes: G06F 3/162 Interface to dedicated audio devices, e.g. audio drivers, interface to CODECs
• CPC Class Codes: G06F 3/165 Management of the audio stream, e.g. setting of volume, audio stream path
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: H04L 67/10 in which an application is distributed across nodes in the network software deployment G06F8/60; multiprogramming arrangements G06F9/46
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04N 21/4143 embedded in a Personal Computer [PC]
• CPC Class Codes: H04N 21/43076 of the same content streams on multiple devices, e.g. when family members are watching the same movie on different devices
• CPC Class Codes: H04N 21/44004 involving video buffer management, e.g. video decoder buffer or video display buffer
• CPC Class Codes: H04N 21/8106 involving special audio data, e.g. different tracks for different languages

Abstract

According to one embodiment, a media system communicates with an aggregate device that includes multiple media output devices. When providing media data for presentation, the system adjusts for device clock drift by resampling the media data provided to a media output device based at least in part on a device clock rate difference between a device clock of one of the media output devices and a device clock of another of the media output devices.

Claims

1. A method of handling communication of information between an entity and multiple devices through respective device drivers, the method comprising:

allocating each of a plurality of buffers to a respective device of a plurality of devices;

reading, by a respective device-side input/output unit (DIO) of each device, information from a respective current position in each buffer; and

writing, by a system-side audio handling input/output unit (SIO), the information, for synchronized presentation by each of the plurality of devices, into each of the plurality of buffers, wherein writing the information into each buffer comprises;

determining a sum of a safety offset and a presentation latency for each corresponding device;

determining a latency offset for each corresponding device, the latency offset being a difference between the sum of the safety offset and presentation offset for the device and a maximum sum of safety offset and presentation offset of the plurality of devices; and

writing the information into each buffer at an insertion point offset in advance by the latency offset for the respective corresponding device from the current position in each buffer from which information is being read.

2. The method of claim 1 further comprising:

upon reaching an end of any buffer while writing information to the buffer, performing, by the SIO, a wrap-around operation to continue writing the information beginning at a start of the buffer; and

upon reaching an end of any buffer while reading information from the buffer, performing, by the corresponding DIO, a wrap-around operation to continue reading the information beginning at the start of the buffer.

3. The method of claim 2 further comprising:

storing timestamp information when a DIO performs a wrap-around operation while reading information from a corresponding buffer, the timestamp information usable by the SIO to determine how fast a clock of the device runs.

4. The method of claim 1, wherein the safety offset for each device indicates a minimum amount ahead for writing the information.

5. The method of claim 1, wherein each device is an audio playing device, and each buffer is a ring buffer.

6. A system comprising:

one or more processors; and

a non-transitory storage device storing instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising;

allocating each of a plurality of buffers to a respective device of a plurality of devices;

reading, by a respective device-side input/output unit (DIO) of each device, information from a respective current position in each buffer; and

writing, by a system-side audio handling input/output unit (SIO), the information, for synchronized presentation by each of the plurality of devices, into each of the plurality of buffers, wherein writing the information into each buffer comprises;

determining a sum of a safety offset and a presentation latency for each corresponding device;

determining a latency offset for each corresponding device, the latency offset being a difference between the sum of the safety offset and presentation offset for the device and a maximum sum of safety offset and presentation offset of the plurality of devices; and

writing the information into each buffer at an insertion point offset in advance by the latency offset for the respective corresponding device from the current position in each buffer from which information is being read.

7. The system of claim 6, the operations further comprising:

upon reaching an end of any buffer while writing information to the buffer, performing, by the SIO, a wrap-around operation to continue writing the information beginning at a start of the buffer; and

upon reaching an end of any buffer while reading information from the buffer, performing, by the corresponding DIO, a wrap-around operation to continue reading the information beginning at the start of the buffer.

8. The system of claim 7, the operations further comprising:

storing timestamp information when a DIO performs a wrap-around operation while reading information from a corresponding buffer, the timestamp information usable by the SIO to determine how fast a clock of the device runs.

9. The system of claim 6, wherein the safety offset for each device indicates a minimum amount ahead for writing the information.

10. The system of claim 6, wherein each device is an audio playing device, and each buffer is a ring buffer.

11. A non-transitory storage device storing instructions that, when executed by one or more processors, cause the one or more processors to perform operations comprising:

allocating each of a plurality of buffers to a respective device of a plurality of devices;

reading, by a respective device-side input/output unit (DIO) of each device, information from a respective current position in each buffer; and

writing, by a system-side audio handling input/output unit (SIO), the information, for synchronized presentation by each of the plurality of devices , into each of the plurality of buffers, wherein writing the information into each buffer comprises;

determining a sum of a safety offset and a presentation latency for each corresponding device;

determining a latency offset for each corresponding device, the latency offset being a difference between the sum of the safety offset and presentation offset for the device and a maximum sum of safety offset and presentation offset of the plurality of devices; and

writing the information into each buffer at an insertion point offset in advance by the latency offset for the respective corresponding device from the current position in each buffer from which information is being read.

12. The non-transitory storage device of claim 11, the operations further comprising:

upon reaching an end of any buffer while writing information to the buffer, performing, by the SIO, a wrap-around operation to continue writing the information beginning at a start of the buffer; and

upon reaching an end of any buffer while reading information from the buffer, performing, by the corresponding DIO, a wrap-around operation to continue reading the information beginning at the start of the buffer.

13. The non-transitory storage device of claim 12, the operations further comprising:

storing timestamp information when a DIO performs a wrap-around operation while reading information from a corresponding buffer, the timestamp information usable by the SIO to determine how fast a clock of the device runs.

14. The non-transitory storage device of claim 11, wherein the safety offset for each device indicates a minimum amount ahead for writing the information.

15. The non-transitory storage device of claim 11, wherein each device is an audio playing device, and each buffer is a ring buffer.