[FFmpeg-devel] [PATCH] Fix AAC prediction in when used in conjunction with the CPE

Alex Converse alex.converse
Thu Dec 4 00:27:56 CET 2008


It appears that I neglected to test my AAC predicition implementation
with streams that a CPE with a common window or intensity stereo. The
attached patch fixes this. This should fix the am02 series of
reference streams.

Note: I chose to deviate from the textual description of the
interaction between prediction and intensity stereo given in
14496-3:2005 for parity with the reference software.

>From 14496-3:
  For scalefactor bands coded in intensity stereo the corresponding
predictors in the right channel are switched to "off" thus effectively
overriding the status specified by the prediction_used mask. The
update of these predictors is done by feeding the intensity stereo
decoded spectral values of the right channel as the "last quantized
value" xrec(n-1). These values result from the scaling process from
left to right channel as described in the pseudo code.

However in reference files adifdec.c and intensity.c, pre-intensity
right channel values are sent into prediction.

Alex Converse
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