Texas Instruments DM6467, Руководство пользователя

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Introduction
1-2
1.1 Overview of XDAIS and XDM
TI’s multimedia codec implementations are based on the eXpressDSP
Digital Media (XDM) standard. XDM is an extension of the eXpressDSP
Algorithm Interface Standard (XDAIS).
1.1.1 XDAIS Overview
An eXpressDSP-compliant algorithm is a module that implements the
abstract interface IALG. The IALG API takes the memory management
function away from the algorithm and places it in the hosting framework.
Thus, an interaction occurs between the algorithm and the framework. This
interaction allows the client application to allocate memory for the algorithm
and also share memory between algorithms. It also allows the memory to
be moved around while an algorithm is operating in the system. In order to
facilitate these functionalities, the IALG interface defines the following
APIs:
‰
algAlloc()
‰
algInit()
‰
algActivate()
‰
algDeactivate()
‰
algFree()
The
algAlloc()
API allows the algorithm to communicate its memory
requirements to the client application. The
algInit()
API allows the
algorithm to initialize the memory allocated by the client application. The
algFree()
API allows the algorithm to communicate the memory to be
freed when an instance is no longer required.
Once an algorithm instance object is created, it can be used to process
data in real-time. The
algActivate()
API provides a notification to the
algorithm instance that one or more algorithm processing methods is about
to be run zero or more times in succession. After the processing methods
have been run, the client application calls the
algDeactivate()
API prior
to reusing any of the instance’s scratch memory.
The IALG interface also defines three more optional APIs
algControl()
,
algNumAlloc()
, and
algMoved()
. For more details on these APIs, see
TMS320 DSP Algorithm Standard API Reference (literature number
SPRU360).
1.1.2 XDM Overview
In the multimedia application space, you have the choice of integrating any
codec into your multimedia system. For example, if you are building a
video decoder system, you can use any of the available video decoders
(such as MPEG4, H.263, or H.264) in your system. To enable easy
integration with the client application, it is important that all codecs with
similar functionality use similar APIs. XDM was primarily defined as an
extension to XDAIS to ensure uniformity across different classes of codecs