get_level

Determines the level of a stream as defined in ISO/IEC 14496-3.

For AAC LC streams, the constraints from the AAC audio profile are applied. For AAC Main, LTP, SSR and others, the Main profile is used.

The audio_config parameter follows the following format, starting from the most significant bit of the first byte:

* Bit 0:4 contains the AudioObjectType (if this is 0x5, then the real AudioObjectType is carried after the rate and channel data) * Bit 5:8 contains the sample frequency index (if this is 0xf, then the next 24 bits define the actual sample frequency, and subsequent fields are appropriately shifted). * Bit 9:12 contains the channel configuration

Parameters:

audio_config	a pointer to the AudioSpecificConfig as specified in the Elementary Stream Descriptor (esds) in ISO/IEC 14496-1.
len	Length of audio_config in bytes

Returns:

The level as a const string and null if the level could not be determined.