UnpackFrameHeader MP3

Unpacks audio frame header.

Syntax

IppStatus ippsUnpackFrameHeader_MP3(Ipp8u** ppBitStream, IppMP3FrameHeader* pFrameHeader);

Parameters

ppBitStream	Pointer to the pointer to the first byte of the MP3 frame header; it is updated in the function.
pFrameHeader	Pointer to the MP3 frame header structure.

Description

The function ippsUnpackFrameHeader_MP3 is declared in the ippac.h file. This function unpacks the audio frame header. If cyclic redundancy check (CRC) is enabled, this function also unpacks the CRC word.

Before calling ippsUnpackFrameHeader_MP3, you must locate the bit stream synchronization word and ensure that ppBitStream points to the first byte of the 32-bit frame header.

If CRC is enabled, the assumption is that the 16-bit CRC word is adjacent to the 32-bit frame header, as defined in the MP3 standard. Before returning to the caller, the function updates the pointer ppBitStream so that it references the next byte after the frame header or the CRC word.

The first byte of the 16-bit CRC word is stored in pFrameHeader ->CRCWord(15:8), and the second byte is stored in pFrameHeader ->CRCWord(7:0).

The function does not detect corrupted frame headers.

Return Values

ippStsNoErr	Indicates no error.
ippStsNullPtrErr	Indicates an error when ppBitStreamp or FrameHeader is NULL.