Systems and methods for running priority-based application threads on a realtime component

• US 7,599,753 B2
• Filed: 09/21/2001
• Issued: 10/06/2009
• Est. Priority Date: 09/23/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Mohanraj, Shanmugam, Taylor, Jeffrey Eames, Ballantyne, Joseph C.
• Primary Examiner(s): Kuntz; Curtis
• Assistant Examiner(s): Sellers; Daniel R
• Application Number:
  US09/960,873
• Publication Number:
  US 20020107594A1
• Time in Patent Office: 2,937 Days
• Field of Search: 700/94, 710 36- 61, 711/209, 381/119
• US Class Current: 700/94
• CPC Class Codes: G06F 9/544 Buffers; Shared memory; Pipes

Abstract

Systems and methods for processing data from priority-based operating system threads within a realtime component are described. The component submits blank buffers to hardware. The component receives data from priority based operating system threads and processes and writes the data from within an independent second real-time thread to buffers before the buffers into which the data is written are used by the hardware. Hardware buffers are created offset from memory page boundaries such that the least significant bits of any memory address referencing the start of the buffer uniquely identify it and can be used as an index into a circular buffer queue to determine which buffer is currently being processed. Data is always processed and written into a buffer that is a predetermined range of buffers in front of the buffer currently being processed by the hardware.

Claims

1. An audio mixer, comprising:

a buffer submission module configured to create multiple buffers having no data and submit empty buffers to audio hardware in a buffer queue to reserve a time slot for the audio hardware to play data that will subsequently be processed into the empty buffers, the empty buffers being arranged serially in the buffer queue, wherein the audio hardware comprises a sound card and wherein before the sound card attempts to play an empty buffer that has been submitted to the sound card, the audio mixer fills the empty buffer with audio data received from one or more audio applications;

a tracking module configured to identify a buffer that is currently being processed by the audio hardware, wherein the tracking module allows the audio mixer to know an exact memory location corresponding to audio data is being played for a given time;

a mix loop module configured to receive one or more data inputs from the one or more audio applications and process the data inputs into a buffer after the buffer has been submitted without any audio data to the audio hardware but before the buffer is processed for playing the audio data by the audio hardware, wherein the mix loop module allows the audio mixer to determine when an empty buffer is just ahead of the audio hardware and mix into that buffer to provide a playable buffer having audio data that will be played, wherein the mix loop module is configured to mix a certain amount of buffers before the buffers are played by the audio hardware and to synchronize mixing with playing by the audio hardware such that if the buffers are mixed at a faster or slower rate than the audio hardware is playing the buffers, then the mix loop module compensates mixing so that the mixing and the playing remain in synchronization, wherein the mix loop module is configured to mix at least two buffers ahead of a buffer being played, but not more than four buffers ahead; and

wherein the audio applications use one or more priority-based operating system threads to submit data to the mix loop module, and the audio data is processed and written to the buffers from within a realtime thread.

2. The audio mixer as recited in claim 1, wherein the buffer submission module is further configured to clear a buffer after the buffer has been processed by the audio hardware and to resubmit the cleared buffer in the buffer queue.

3. The audio mixer as recited in claim 1, wherein the audio hardware includes a audio hardware driver that processes data sent to and received by the audio hardware.

4. The audio mixer as recited in claim 1, wherein:

the buffer submission module is further configured to create the multiple buffers so that the start of each buffer is offset from a memory page boundary by a multiple of a fixed number of bytes; and

the tracking module is further configured to receive a play position from the audio hardware, the play position containing the starting memory address of the buffer currently being processed and the offset within the buffer to a current play location, and to identify a buffer that is currently being processed by the audio hardware by mapping the least significant bits of a starting memory address for a buffer to a buffer position in the buffer queue.

5. The audio mixer as recited in claim 4, wherein, the multiple of a fixed number of bytes is a power of 2.

6. The audio mixer as recited in claim 4, wherein:

the fixed number of bytes further comprises sixteen bytes; and

the number of least significant bits of the memory address is twelve.

7. The audio mixer as recited in claim 4, wherein the offset from a memory page boundary further comprises sixteen times a zero-based ordinal position of the buffer in the buffer queue.