Reconstructing AAC CPE

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Revision as of 17:58, 5 March 2006 by Multimedia Mike (talk | contribs) (outline the reconstruction process)
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Part of Understanding AAC

This page describes the process of reconstructing PCM data based on the decoded CPE parameters in an AAC bitstream.

Reconstruction Process

   +-ic_predict.c:ic_prediction() (main profile)
   +-ic_predict.c:pns_reset_pred_state() (main profile)
   +-(LTP & LD stuff)

reconstruct_channel_pair(2 ic_streams, 2 spec_data arrays(16 bit ints))

 declare 2 1024-element float arrays for spectral coefficients (spec_coeff1 and spec_coeff2)
 quant_to_spec(ics1, spec_data1, ics1)
 quant_to_spec(ics2, spec_data2, ics2)
 if ics1.ms_mask_present
   pns_decode(ics1, ics2, spec_coef1, spec_coeff2)
   pns_decode(ics1, spec_coef1)
   pns_decode(ics2, spec_coef2)
 ms_decode(ics1, ics2, spec_coef1, spec_coef2)
 is_decode(ics1, ics2, spec_coef1, spec_coef2)
 // main profile decoding
 // LTP decoding
 tns_decode(ics1, spec_coeff1)
 tns_decode(ics2, spec_coeff2)
 // DRC stuff
 ifilter_bank(ics1, spec_coeff1)
 ifilter_bank(ics2, spec_coeff2)
 save window shape for next frame (I thought frames were independent)
 // LTP stuff
 // SBR stuff






ic_prediction() (pertains to main profile)

pns_reset_pred_state() (pertains to main profile)

tns_decode_frame() (pertains to LTP and LD stuff)

drc_decode() (pertains to LTP and LD stuff)

ifilter_bank() (pertains to LTP and LD stuff)

ssr_decode() (pertains to LTP and LD stuff)

lt_update_state() (pertains to LTP and LD stuff)

sbrDecodeInit() (pertains to LTP and LD stuff)

sbrDecodeCoupleFrame() (pertains to LTP and LD stuff)