Intel High Definition Audio

Intel High Definition Audio (IHDA) (also called HD Audio or development codename Azalia) is a specification for the audio sub-system of personal computers. It was released by Intel in 2004 as the successor to its AC'97 PC audio standard.

Features of the specification include:

• Up to 15 input and 15 output streams
• Up to 16 PCM audio channels per stream
• Sample resolutions of 8–32 bits
• Sample rates of 6–192 kHz
• Support for audio codecs (e.g., ADC, DAC), modem codecs, and vendor-defined codecs
• Discoverable codec architecture
• Fine-grained codec power-control
• Audio jack detection, sensing, and retasking

However, as of 2008, most audio hardware manufacturers did not implement the full specification, especially 32-bit sampling resolution. Motherboards typically do not have any more than eight onboard output channels (7.1 surround sound) and four input channels (back and front panel microphone inputs, and a back-panel stereo line-in). Users requiring more audio I/Os will typically opt for a sound card or an external audio interface, as these devices also provide additional features that are more oriented towards professional audio applications.