DESCRIPTION

Low Delay Advanced Audio Coding (AAC-LD) is the high-quality low-delay audio coding standard within MPEG-4. The MPEG-4 Low Delay Audio Coder is designed to combine the advantages of perceptual audio coding with the low delay necessary for two-way communication. It has achieved wide acceptance in high end video conference terminals and is used in professional broadcasting applications. The codec is closely derived from MPEG-4 Advanced Audio Coding (AAC-LC). It features an algorithmic delay of only 20 ms while offering good compression ratios and high sound quality audio quality for all kinds of audio signals including speech, music and atmospheric sounds. This way, AAC-LD bridges the gap between speech coding schemes and high quality audio coding schemes. Unlike common speech coders, the achieved coding quality scales up with bitrate, and transparent quality can be achieved.

FEATURES

• Suitable for all kinds of audio signals including speech and music
• Audio quality better than ITU-T G.722/G.722.1-C, G.729.1 at the same bit rate
• Audio quality better than mp3 at the same bit rate
• Algorithmic delay of only 20 ms
• Delay of real-time DSP implementation down to 30 ms
• Multi-channel support
• Large range of bit rates possible
• Computational and storage complexity comparable to MPEG-4 AAC-LC
• 480 samples and 512 samples per frame supported
• Error resilient AAC-LD audio object type
• Decoding of mono and stereo streams supported
• eXpressDSP™ Digital Media compliant

AVAILABILITY

ADT MPEG4 AAC LD Encoder is available on the TMS320C6000™ DSP Platform

TI C64x™ (TMS320C64x™), TI C64x+™/DaVinci™ (DM644x™)

SPECIFICATIONS

MIPS (Peak) CPU Resource and Memory Resource Requirements

• C64x

All Memory usage is given in units of byte.

Function	MIPS	Program Memory	Data Memory	Per-Channel Data Memory
Encode	31	103 k	50 k	30 k
Decode	13	71 k	18 k	30 k

• C64x+

All Memory usage is given in units of byte.

Function	MIPS	Program Memory	Data Memory	Per-Channel Data Memory
Encode	29.5	98 k	50 k	30 k
Decode	12.4	67.5 k	18 k	30 k

API FUNCTIONS

DECODE_create (…) creates an instance of the DECODE algorithm and returns a handle to the object

DECODE_decode (…) processes the decoder

DECODE_delete (…) deletes the instance of the dynamically created object referenced to by the handle