Optimized Heilx AAC Decoder for ARM

简介：
本项目旨在为ARM架构优化Heilx AAC解码器，显著提升音频解码效率和性能，适用于移动设备和嵌入式系统。 Fixed-point HE-AAC Decoder Developed by RealNetworks, 2005 --- ### Overview This module contains a high-performance HE-AAC decoder designed for 32-bit fixed-point processors. The following is a summary of what the decoder supports and does not support: **Supported:** - MPEG2 and MPEG4 low complexity decoding (intensity stereo, M-S, TNS, PNS) - Spectral band replication (SBR) in high-quality mode - Mono, stereo, and multichannel modes - ADTS, ADIF file formats, and raw data block format **Not currently supported:** - Main or SSR profile decoding - Long-term prediction (LTP) - Coupling channel elements (CCE) - 960/1920-sample frame size - Low-power mode SBR - Downsampled (single-rate) SBR - Parametric stereo ### Highlights The decoder is optimized for ARM processors and includes a reference x86 implementation. The codebase consists of C and assembly language only, with no requirement for C++. Features include: - Reentrant and statically linkable design - Low memory usage (details in the documentation) - Option to use Intel Integrated Performance Primitives ### Supported Platforms and Toolchains The codec should run on any 32-bit fixed-point processor capable of performing full 32x32-bit multiplies. The following processors and toolchains are supported: - x86 with Microsoft Visual C++ or GNU toolchain (gcc) - ARM with ARM Developer Suite, Microsoft Embedded Visual C++, or GNU toolchain For the fastest performance on non-standard platforms, consider using ADS to output assembly code which can then be fed into your assembler of choice. ### Adding Support for New Processors and Toolchains Adding support involves implementing inline assembly functions in `real/assembly.h` and optionally rewriting or adding optimized assembly files. Supporting a new toolchain is straightforward by following the sample projects or Helix makefiles as templates. ### Multichannel Support For multichannel decoding, set AAC_MAX_NCHANS to your desired maximum number of channels (default = 2) in `pub/aacdec.h` and recompile. ### Directory Structure - `fixpt/`: Platform-independent code, tables, public API. - `fixpt/docs`: Memory and CPU usage figures, callgraphs. - `fixpt/hxwrap`: Helix wrapper code and makefiles. - `fixpt/pub`: Public header files. - `fixpt/testwrap`: Sample command-line test application. ### Code Organization The source is organized into: - Main decode functions in `aacdec.c`, common tables in `aactabs.c`. - Low-level codec API calls in `pub/aaccommon.h` and high-level API for applications in `aacdec.h`. To build the AAC decoder library, compile top-level files with either RealNetworks source code or IPP libraries.