Patent Application
20060047503
The present invention relates to sound processors, and more particularly to a system and method for controlling sound data.
Sound processors produce sound by controlling digital data, which is transformed into a voltage by means of a digital-to-analog converter (DAC). This voltage is used to drive a speaker system to create sound. Sound processors, which are wave-table-based, use sound data from memory as a source, and modify that sound by altering the pitch, controlling the volume over time, transforming the sound through the use of filters, and employing other effects. These modifications to the source sound are controlled through a set of parameters.
Polyphonic sound processors create multiple sounds simultaneously by creating independent sound streams and adding them together. Each separate sound that can be played simultaneously is referred to as a voice, and each voice will have its own set of control parameters. The set of control parameters to control a voice is referred to as a parameter block.
Also, with a large number of control parameters, it becomes important for both the host processor 52 and the sound processor 54 to access the control parameter blocks 62 without conflict. It may require many cycles for the host processor 52 to update the control parameters, and it may require many cycles for the sound processor to read all of the control parameters. Since many of the control parameters are related, if no method were used to avoid conflict, the sound processor 52 may read an inconsistent set of control parameters for a voice.
One conventional solution, which avoids conflict by the host processor 52 and the sound processor 54 in accessing parameter blocks, is to use locking mechanisms 64. Typically, there is a locking mechanism for each parameter block. If the host processor 52 or the sound processor 54 wants to access a particular parameter block, the host processor 52 or sound processor 54 will test a lock bit. If the lock bit was not set, the host processor 52 or sound processor 54 will set the lock bit and know that it can access the parameter block. If the lock bit was set, then the parameter block is currently being accessed, and the host processor 52 or sound processor 54 must wait until the parameter block is not locked before accessing it. The disadvantage of this solution is that each processor must wait for the parameter block to be free before accessing it. This may result in wasted time and reduced performance.
Another problem with this solution is that when locking a parameter block in system memory, a “test and set” instruction is necessary. This instruction is necessary because two modules may test whether the block is locked before either has a chance to set the lock bit. In this case, an error condition can occur where both modules think that they can access the memory block.
Accordingly, what is needed is a more efficient system and method for controlling access to parameter blocks of a sound processor. The system and method should be able to simple, cost effective and capable of being easily adapted to existing technology. The present invention addresses such a need.
The present invention provides a system and method for controlling access to parameter blocks of a sound processor. According to the method and system disclosed herein, the present invention includes a host, a sound processor coupled to the host, and at least two copies of a parameter block associated with the sound data. The sound processor can access a first copy of the at least two copies while the host is accessing a second copy of the at least two copies. As a result, parameter blocks are freely updated by the host processor and freely read by the sound processor without conflict and without performance loss.
The present invention relates to sound processors, and more particularly to a system and method for controlling sound data. The following description is presented to enable one of ordinary skill in the art to make and use the invention, and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown, but is to be accorded the widest scope consistent with the principles and features described herein.
The present invention provides a system and method for controlling sound data, where two copies of each parameter block, which contain voice control parameters, are provided. Having two copies of each parameter block enables the host processor to make updates to a voice's control parameters at the same time the sound processor reads the same voice's control parameters.
Although the present invention disclosed herein is described in the context of sound data, the present invention may apply to other types of data and still remain within the spirit and scope of the present invention.
When the host processor 102 has completed making modifications to a given voice's parameter block, it will toggle a control bit to notify the sound processor 104 to switch ownership to the newly modified parameter block. The alternate parameter block for that voice is then owned by host processor 102.
The parameter blocks 120 and 122 are preferably indexed using two parameter block lists. As such, the two copies of the parameter blocks for all voices are held in two parameter block lists. This allows the address of a given voice's parameter block to be easily determined through indexing. At any given time, the “active” parameter block, which is the parameter block being used by the sound processor to generate sound, will be in one of the two parameter block lists. The active parameter block will be at a fixed offset from the beginning address of the parameter block list in which it resides. It should be noted that all of the active parameter blocks for the voices do not need to be in the same parameter block list. Some voices' active parameter blocks may be in one parameter block List while other voices' active parameter blocks are in the other parameter block list.
The control bits that control which copy of each voice's parameter block is active are held in the sound processor, and are used by the sound processor as each voice needs to access its parameter block. Alternatively, the control bits can reside in a different module. For example, they could reside in the DMA engine. Depending on the setting of a voice's control bit, the voice's parameter block will be fetched from the appropriate parameter block list.
The sound processor contains the following registers. The parameter block list A address register 402 contains the starting address for the parameter block list A 502. Similarly, a parameter block list B address register 404 contains the starting address for the parameter block list B 504.
A group of eight parameter block select registers 406 holds the control bits for the 256 voices. If a voice's control bit is “0”, then it will fetch the parameter block from the parameter block list A. If a voice's control bit is “1”, then it will fetch the parameter block from the parameter block list B.
The host processor writes the parameter block list A address register 402 with the value 0x100000 and the parameter block list B address register 404 with the value 0x200000. If at reset time all the parameter block select registers 406 contain “0x0”, then the sound processor will use the parameter blocks contained in parameter block list A 502 for all the voices. The host processor can modify the parameter blocks in parameter block list B 504 without any conflict with the sound processor. For example, in order to change the control parameters for Voice 3, the host processor will modify the parameters in Parameter Block 3 in parameter block list B 504. The address of Parameter Block 3 is address 0x200600. The host processor will then write the parameter block select 0 register to set bit 3 to “1”. If the sound processor needs to access the Parameter Block 3 while the host processor is accessing the Parameter Block 3, the sound processor will be directed to the Parameter Block 3 in the parameter block list A 502. Accordingly, a conflict between the host and sound processors is avoided.
One of ordinary skill in the art will readily recognize that there could be variations to the embodiments, and that any variations would be within the spirit and scope of the present invention. For example, instead of using two parameter block lists, the two sets of parameter blocks can be indexed using one list with a well-defined layout. As such, the single parameter block list would contain two parameter blocks for each voice, and the active parameter block would be determined by the control bit. Also, the ordering of the parameter blocks within the parameter block lists may be different from the order described herein. For example, the parameter blocks may be ordered from highest-numbered voice to lowest-numbered voice.
According to the system and method disclosed herein, the present invention provides numerous benefits. For example, the host processor can make updates to a voice's control parameters at the same time the sound processor reads the same voice's control parameters. No waiting penalty is incurred.
Embodiments of the present invention also eliminate the need for locking mechanisms, because the host processor and sound processor do not try to access the same memory block.
A method and system for controlling sound data has been disclosed. The present invention has been described in accordance with the embodiments shown. One of ordinary skill in the art will readily recognize that there could be variations to the embodiments, and that any variations would be within the spirit and scope of the present invention. For example, the present invention can be implemented using hardware, software, a computer readable medium containing program instructions, or a combination thereof. Software written according to the present invention is to be either stored in some form of computer-readable medium such as memory or CD-ROM, or is to be transmitted over a network, and is to be executed by a processor. Consequently, a computer-readable medium is intended to include a computer readable signal, which may be, for example, transmitted over a network. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.
