[flac-dev] "keep qlp coeff precision such that only 32-bit math is required"

lvqcl lvqcl.mail at gmail.com
Wed Apr 22 13:45:16 PDT 2015

Martijn van Beurden wrote:

> Yes, but that MAX value is used to loop over the
> qlp_coeff_precision values between MIN and MAX. So, if the
> qlp_coeff_precision value is limited in the loop but MAX is not
> limited, the loop does the exact same thing multiple times: a
> waste of time. Therefore, only the MAX should be limited.
> I don't think the logic is needed directly after
>> min_qlp_coeff_precision = max_qlp_coeff_precision = encoder->protected_->qlp_coeff_precision;
> because that value is either chosen by the encoder (it is a
> lookup value, and is always small enough not to trigger this,
> set in stream_encoder.c around line 700) or it is set through
> the encoder, in which case it should probably not be overriden
> without notice.

Currently evaluate_lpc_subframe_() automatically adjusts qlp_coeff_precision
when a user sets non-standard order value (via -l option). I don't think
that it's incorrect behavior. Why not?

(And my initial point was that the current limit of qlp_coeff_precision is not enough,
and 32-bit datapath is *not* ensured for 16-bit input audio).

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