[FFmpeg-devel] [PATCH] G.729 Fixed-codebook vector decoding

Vladimir Voroshilov voroshil
Sat Jun 27 04:27:23 CEST 2009

2009/6/27 Michael Niedermayer <michaelni at gmx.at>:
> On Sat, Jun 27, 2009 at 02:05:27AM +0700, Vladimir Voroshilov wrote:
>> Memset is required, since vector should contain only several non-zero pulses
> if the thing is sparse, memset could maybe be replaced by just setting
> the non zero values to zero, in that sense many operationson on sparse
> vectors can be done more efficiently than working on an array of zeros
> with one non zero value, which if it applies here means you have to
> rewrite the related code to be more efficient


Does you mean "invert" vector (replace zero with non-zero and vice versa) ?
What values whould contain non-zero parts in your suggestion?

Here is how i uderstand fixed-codebook vector generation.

Fixed-codebook vector defines where four (or three, depends on mode)
pulses of sound are placed in
current frame (which is zero at this stage). Afaik, fixed-codebook
vector defines signal which in "new"
in current frame and is not continuation oprevious frame's sound.
Routine sets 1 at this positions, setting all other to 0.

"1" related to pulse of sound, "0" means silence.

Later this vector will be weightly summed with excitation signal.

Thus, either your suggestion is deep math or heavy optimization which
i can't understand.

Vladimir Voroshilov     mailto:voroshil at gmail.com
JID: voroshil at gmail.com, voroshil at jabber.ru
ICQ: 95587719

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