[FFmpeg-devel] [PATCH] Common ACELP routines (3/3) - LPC decoding routines
Vladimir Voroshilov
voroshil
Fri Apr 25 18:57:24 CEST 2008
On 4/25/08, Vladimir Voroshilov <voroshil at gmail.com> wrote:
> Michael Niedermayer wrote:
> > On Fri, Apr 25, 2008 at 10:24:25AM +0700, Vladimir Voroshilov wrote:
> > > Michael Niedermayer wrote:
> > > > On Fri, Apr 25, 2008 at 08:26:35AM +0700, Vladimir Voroshilov wrote:
> > > > [...]
> > > > > +void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int
> lsfq_min, int lsfq_max)
> > > > > +{
> > > > > + int i, j;
> > > > > +
> > > > > + /* sort lsfq in ascending order. float bubble agorithm, O(n)*/
> > > >
> > > > > + for(i=9; i<9; i++)
> > > >
> > > > i do not think that will work
> > >
> > > It passed all tests what means that data were already ordered.
> > > Anyway since there is nothing in spec about LSFs ordering I'd
> > > prefer keep sorting there.
> > [...]
> >
> > > +/**
> > > + * \brief decodes polynomial coefficients from LSP
> > > + * \param f [out] (Q24) decoded polynomial coefficients
> > > + * \param lsp (Q15) LSP coefficients
> > > + */
> > > +static void lsp2poly(int* f, const int16_t* lsp)
> > > +{
> > > + int i, j;
> > > +
> > > + f[0] = 0x1000000; // 1.0 in Q24
> > > + f[1] = -lsp[0] << 10; // *2 and Q15 -> Q24
> > > +
> > > + for(i=2; i<=5; i++)
> > > + {
> > > + f[i] = f[i-2];
> > > +
> > > + for(j=i; j>1; j--)
> > > +#ifdef G729_BITEXACT
> > > + f[j] -= (mul_32_16(f[j-1]>>1, lsp[2*i-2])<<2) - f[j-2];
> > > +#else
> > > + f[j] -= (mul_32_16(f[j-1], lsp[2*i-2])<<1) - f[j-2];
> >
> > mul_32_16 does >>15, you do <<1 afterwards, thats redundant and looses
> > precission, you could as well >> by 14
>
> I've found that i can use existing MULH and MULL (and replaced it
> everywhere in local tree already).
> I've defined FRAC_BITS=15 before including mathops.h and
> called MULL everywhere except this place.
> I'm trying to eliminate extra shifts here by reducing fixed point base
> (looks like two least significant bits of f[i] are always zero, but I'm not
> sure).
Finished. Extra shifts are eliminated and code is still bitexact.
>
> >
> >
> > [...]
> > > +/**
> > > + * \brief Convert LSF to LSP
> > > + * \param lsp [out] LSP coefficients (-(1<<15) <= lsp < (1<<15))
> > > + * \param lsf LSF coefficients (0 <= lsf < PI * (1<<13))
> > > + *
> > > + * \remark It is safe to pass the same array in lsf and lsp parameters
> > > + */
> > > +void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp);
> >
> > the comment and the function names contradict each other lsp2lpc vs.
> lsf2lsp
> >
> >
> > > +
> > > +/**
> > > + * \brief LSP to LP conversion (3.2.6 of G.729)
> > > + * \param lp [out] (Q12) decoded LP coefficients
> > > + * \param lsp (Q15) LSP coefficients
> > > + */
> > > +void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf);
>
> > same issue
>
> Fixed in local tree.
>
>
> > also please change the Q12/15 notation to some normal fixed point one with
> > min/one/max
>
> Like this?:
>
> /**
> * \param param1 bla bla bla
> ...
> * \return some value
> *
> * allowed values for param1:
> * min: -0x10000
> * max: 0x10000
> * one 0x01000
> */
>
> Or something different?
> Give me sample please.
Waiting for answer.
Currently kept Q[n] notation as is.
>
> --
> Regards,
> Vladimir Voroshilov mailto:voroshil at gmail.com
> Omsk State University
> JID: voroshil at jabber.ru
> ICQ: 95587719
>
--
Regards,
Vladimir Voroshilov mailto:voroshil at gmail.com
JID: voroshil at gmail.com, voroshil at jabber.ru
ICQ: 95587719
-------------- next part --------------
diff --git a/libavcodec/lsp.c b/libavcodec/lsp.c
new file mode 100644
index 0000000..f8692d1
--- /dev/null
+++ b/libavcodec/lsp.c
@@ -0,0 +1,119 @@
+/*
+ * LSP routines for ACELP-based codecs
+ *
+ * Copyright (c) 2008 Vladimir Voroshilov
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <inttypes.h>
+
+#include "avcodec.h"
+#define FRAC_BITS 14
+#include "mathops.h"
+#include "lsp.h"
+#include "acelp_math.h"
+
+void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int lsfq_min, int lsfq_max)
+{
+ int i, j;
+
+ /* sort lsfq in ascending order. float bubble agorithm, O(n)*/
+ for(i=0; i<9; i++)
+ for(j=i; j>=0 && lsfq[j] > lsfq[j+1]; j--)
+ FFSWAP(int16_t, lsfq[j], lsfq[j+1]);
+
+ for(i=0;i<10; i++)
+ {
+ lsfq[i] = FFMAX(lsfq[i], lsfq_min);
+ lsfq_min = lsfq[i] + lsfq_min_distance;
+ }
+ lsfq[9] = FFMIN(lsfq[9], lsfq_max);//Is warning required ?
+}
+
+void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf)
+{
+ int i;
+
+ /* Convert LSF to LSP, lsp=cos(lsf) */
+ for(i=0;i<10; i++)
+ // 20861 = (1<<16) / PI
+ lsp[i] = ff_cos(lsf[i] * 20861 >> 15);
+}
+
+/**
+ * \brief decodes polynomial coefficients from LSP
+ * \param f [out] (Q22) decoded polynomial coefficients
+ * \param lsp (Q15) LSP coefficients
+ */
+static void lsp2poly(int* f, const int16_t* lsp)
+{
+ int i, j;
+
+ f[0] = 0x400000; // 1.0 in Q22
+ f[1] = -lsp[0] << 8; // *2 and Q15 -> Q22
+
+ for(i=2; i<=5; i++)
+ {
+ f[i] = f[i-2];
+ for(j=i; j>1; j--)
+ f[j] -= MULL(f[j-1], lsp[2*i-2]) - f[j-2]; // Q22 * Q15 * 2 -> Q22
+
+ f[1] -= lsp[2*i-2] << 8;
+ }
+}
+
+void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp)
+{
+ int i;
+ int f1[6]; // Q22
+ int f2[6]; // Q22
+
+ lsp2poly(f1, lsp );
+ lsp2poly(f2, lsp+1);
+
+ /* 3.2.6 of G.729, Equations 25 and 26*/
+ lp[0] = 4096;
+ for(i=1; i<6; i++)
+ {
+ int ff1 = f1[i] + f1[i-1]; // Q22
+ int ff2 = f2[i] - f2[i-1]; // Q22
+
+ ff1 += 1 << 10;
+ lp[i] = (ff1 + ff2) >> 11;
+ lp[11-i] = (ff1 - ff2) >> 11;
+ }
+}
+
+void ff_acelp_lp_decode(int16_t* lp_1st, int16_t* lp_2nd, const int16_t* lsp_2nd, const int16_t* lsp_prev)
+{
+ int16_t lsp_1st[10]; // Q15
+ int i;
+
+ /* LSP values for first subframe (3.2.5 of G.729, Equation 24)*/
+ for(i=0;i<10;i++)
+#ifdef G729_BITEXACT
+ lsp_1st[i] = (lsp_2nd[i] >> 1) + (lsp_prev[i] >> 1);
+#else
+ lsp_1st[i] = (lsp_2nd[i] + lsp_prev[i]) >> 1;
+#endif
+
+ ff_acelp_lsp2lpc(lp_1st, lsp_1st);
+
+ /* LSP values for second subframe (3.2.5 of G.729)*/
+ ff_acelp_lsp2lpc(lp_2nd, lsp_2nd);
+}
diff --git a/libavcodec/lsp.h b/libavcodec/lsp.h
new file mode 100644
index 0000000..137dff9
--- /dev/null
+++ b/libavcodec/lsp.h
@@ -0,0 +1,60 @@
+/*
+ * LSP computing for ACELP-based codecs
+ *
+ * Copyright (c) 2008 Vladimir Voroshilov
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef FFMPEG_ACELP_LPC_H
+#define FFMPEG_ACELP_LPC_H
+
+/**
+ * \brief keep distance between LSFs.
+ * \param lsfq [in/out] LSF to check and adjust
+ * \param lsfq_min_distance minimum distance between LSFs
+ * \param lsfq_min minimum allowed LSF value
+ * \param lsfq_max maximum allowed LSF value
+ */
+void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int lsqf_min, int lsfq_max);
+
+/**
+ * \brief Convert LSF to LSP
+ * \param lsp [out] LSP coefficients (-(1<<15) <= lsp < (1<<15))
+ * \param lsf LSF coefficients (0 <= lsf < PI * (1<<13))
+ *
+ * \remark It is safe to pass the same array in lsf and lsp parameters
+ */
+void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf);
+
+/**
+ * \brief LSP to LP conversion (3.2.6 of G.729)
+ * \param lp [out] (Q12) decoded LP coefficients
+ * \param lsp (Q15) LSP coefficients
+ */
+void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp);
+
+/**
+ * \brief Interpolate LSP for the first subframe and convert LSP -> LP for both subframes (3.2.5 and 3.2.6 of G.729)
+ * \param lp_1st [out] (Q12) decoded LP coefficients for 1st subframe
+ * \param lp_2nd [out] (Q12) decoded LP coefficients for second subframe
+ * \param lsp_2nd (Q15) LSP coefficients of the second subframe
+ * \param lsp_prev (Q15) past LSP coefficients
+ */
+void ff_acelp_lp_decode(int16_t* lp_1st, int16_t* lp_2nd, const int16_t* lsp_2nd, const int16_t* lsp_prev);
+
+#endif // FFMPEG_ACELP_LPC_H
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