[FFmpeg-devel] [PATCH] Common ACELP routines (3/3) - LPC decoding routines
Vladimir Voroshilov
voroshil
Sat Apr 26 09:18:17 CEST 2008
Michael Niedermayer wrote:
> On Fri, Apr 25, 2008 at 11:57:24PM +0700, Vladimir Voroshilov wrote:
> > On 4/25/08, Vladimir Voroshilov <voroshil at gmail.com> wrote:
> [...]
> > > > 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.
>
> [...]
>
> > +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)*/
>
> Its O(n) if already sorted otherwise its O(n^2)
Fixed.
> anyway the patch looks ok except this and the Q* notation
I've added parenthesis to your suggestion to differ fixed-point value
description from regular floating-point constant.
I.e. description looks like (-0x8000 <= (0.15) < 0x8000)
in parameters and just (0.15) in code's comments
P.S. Suggested commit message: "Fixed-point LSP and LPC decoding routines for ACELP-based codecs"
--
Regards,
Vladimir Voroshilov mailto:voroshil at gmail.com
Omsk State University
JID: voroshil at jabber.ru
ICQ: 95587719
-------------- next part --------------
diff --git a/libavcodec/lsp.c b/libavcodec/lsp.c
new file mode 100644
index 0000000..9a09f8d
--- /dev/null
+++ b/libavcodec/lsp.c
@@ -0,0 +1,120 @@
+/*
+ * 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) if data already sorted, O(n^2) - otherwise */
+ 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 = 2.0 / PI in (0.15)
+ lsp[i] = ff_cos(lsf[i] * 20861 >> 15); // divide by PI and (0,13) -> (0,14)
+}
+
+/**
+ * \brief decodes polynomial coefficients from LSP
+ * \param f [out] decoded polynomial coefficients (-0x20000000 <= (3.22) <= 0x1fffffff)
+ * \param lsp LSP coefficients (-0x8000 <= (0.15) <= 0x7fff)
+ */
+static void lsp2poly(int* f, const int16_t* lsp)
+{
+ int i, j;
+
+ f[0] = 0x400000; // 1.0 in (3.22)
+ f[1] = -lsp[0] << 8; // *2 and (0.15) -> (3.22)
+
+ 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]; // (3.22) * (0.15) * 2 -> (3.22)
+
+ f[1] -= lsp[2*i-2] << 8;
+ }
+}
+
+void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp)
+{
+ int i;
+ int f1[6]; // (3.22)
+ int f2[6]; // (3.22)
+
+ 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]; // (3.22)
+ int ff2 = f2[i] - f2[i-1]; // (3.22)
+
+ ff1 += 1 << 10; // for rounding
+ lp[i] = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
+ lp[11-i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
+ }
+}
+
+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]; // (0.15)
+ 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..7fdb66e
--- /dev/null
+++ b/libavcodec/lsp.h
@@ -0,0 +1,63 @@
+/*
+ * 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
+/**
+ (I.F) means fixed-point value with F fractional and I integer bits
+*/
+
+/**
+ * \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 (-0x8000 <= (0.15) < 0x8000)
+ * \param lsf normalized LSF coefficients (0 <= (2.13) < 0x2000 * PI)
+ *
+ * \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] decoded LP coefficients (-0x8000 <= (3.12) < 0x8000)
+ * \param lsp LSP coefficients (-0x8000 <= (0.15) < 0x8000)
+ */
+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] decoded LP coefficients for 1st subframe (-0x8000 <= (3.12) < 0x8000)
+ * \param lp_2nd [out] decoded LP coefficients for second subframe (-0x8000 <= (3.12) < 0x8000)
+ * \param lsp_2nd LSP coefficients of the second subframe (-0x8000 <= (0.15) < 0x8000)
+ * \param lsp_prev past LSP coefficients (-0x8000 <= (0.15) < 0x8000)
+ */
+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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