[FFmpeg-devel] [PATCHv2] avcodec/g728dec: G.728 decoder

[Peter Ross <pross@xvid.org>]

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---
suggestions incorporated.

 libavcodec/Makefile     |   1 +
 libavcodec/allcodecs.c  |   1 +
 libavcodec/codec_desc.c |   7 ++
 libavcodec/codec_id.h   |   1 +
 libavcodec/g728data.h   |  70 +++++++++++++
 libavcodec/g728dec.c    | 220 ++++++++++++++++++++++++++++++++++++++++
 libavcodec/utils.c      |   1 +
 7 files changed, 301 insertions(+)
 create mode 100644 libavcodec/g728data.h
 create mode 100644 libavcodec/g728dec.c

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 95bd5488b6..1028046e89 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -395,6 +395,7 @@ OBJS-$(CONFIG_G723_1_DECODER)          += g723_1dec.o g723_1.o \
                                           acelp_vectors.o celp_filters.o celp_math.o
 OBJS-$(CONFIG_G723_1_ENCODER)          += g723_1enc.o g723_1.o \
                                           acelp_vectors.o celp_filters.o celp_math.o
+OBJS-$(CONFIG_G728_DECODER)            += g728dec.o
 OBJS-$(CONFIG_G729_DECODER)            += g729dec.o lsp.o celp_math.o celp_filters.o acelp_filters.o acelp_pitch_delay.o acelp_vectors.o g729postfilter.o
 OBJS-$(CONFIG_GDV_DECODER)             += gdv.o
 OBJS-$(CONFIG_GEM_DECODER)             += gemdec.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index 4e1b1c9b45..111eadf7ce 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -475,6 +475,7 @@ extern const FFCodec ff_flac_decoder;
 extern const FFCodec ff_ftr_decoder;
 extern const FFCodec ff_g723_1_encoder;
 extern const FFCodec ff_g723_1_decoder;
+extern const FFCodec ff_g728_decoder;
 extern const FFCodec ff_g729_decoder;
 extern const FFCodec ff_gsm_decoder;
 extern const FFCodec ff_gsm_ms_decoder;
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index b734d07ded..d8bd30d0e1 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -3466,6 +3466,13 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .long_name = NULL_IF_CONFIG_SMALL("LC3 (Low Complexity Communication Codec)"),
         .props     = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
     },
+    {
+        .id        = AV_CODEC_ID_G728,
+        .type      = AVMEDIA_TYPE_AUDIO,
+        .name      = "g728",
+        .long_name = NULL_IF_CONFIG_SMALL("G.728"),
+        .props     = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
+    },
 
     /* subtitle codecs */
     {
diff --git a/libavcodec/codec_id.h b/libavcodec/codec_id.h
index 97b70c5bf5..ee02fe4261 100644
--- a/libavcodec/codec_id.h
+++ b/libavcodec/codec_id.h
@@ -552,6 +552,7 @@ enum AVCodecID {
     AV_CODEC_ID_OSQ,
     AV_CODEC_ID_QOA,
     AV_CODEC_ID_LC3,
+    AV_CODEC_ID_G728,
 
     /* subtitle codecs */
     AV_CODEC_ID_FIRST_SUBTITLE = 0x17000,          ///< A dummy ID pointing at the start of subtitle codecs.
diff --git a/libavcodec/g728data.h b/libavcodec/g728data.h
new file mode 100644
index 0000000000..a2ddf5682d
--- /dev/null
+++ b/libavcodec/g728data.h
@@ -0,0 +1,70 @@
+/*
+ * G.728 decoder
+ *
+ * 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 AVCODEC_G728DATA_H
+#define AVCODEC_G728DATA_H
+
+#include <stdint.h>
+#include "libavutil/macros.h"
+
+#define IDIM 5 /* Vector dimension (excitation block size) */
+#define LPC 50 /* Synthesis filter order */
+#define LPCLG 10 /* Log-gain predictor order */
+#define NFRSZ 20 /* Frame size (adaptation cycle size in samples */
+#define NONR 35 /* Number of non-recursive window samples for synthesis filter */
+#define NONRLG 20 /* Number of non-recursive window samples for log-gain predictor */
+#define NUPDATE 4 /* Predictor update period (in terms of vectors) */
+
+#define NSBSZ (LPC + NONR + NFRSZ)
+#define NSBGSZ (LPCLG + NONRLG + NUPDATE)
+
+// Hybrid window for the synthesis filter
+static const uint16_t g728_wnr[NSBSZ] = {
+     1565,  3127,  4681,  6225,  7755,  9266, 10757, 12223, 13661, 15068,
+    16441, 17776, 19071, 20322, 21526, 22682, 23786, 24835, 25828, 26761,
+    27634, 28444, 29188, 29866, 30476, 31016, 31486, 31884, 32208, 32460,
+    32637, 32739, 32767, 32721, 32599, 32403, 32171, 31940, 31711, 31484,
+    31259, 31034, 30812, 30591, 30372, 30154, 29938, 29724, 29511, 29299,
+    29089, 28881, 28674, 28468, 28264, 28062, 27861, 27661, 27463, 27266,
+    27071, 26877, 26684, 26493, 26303, 26114, 25927, 25742, 25557, 25374,
+    25192, 25012, 24832, 24654, 24478, 24302, 24128, 23955, 23784, 23613,
+    23444, 23276, 23109, 22943, 22779, 22616, 22454, 22293, 22133, 21974,
+    21817, 21661, 21505, 21351, 21198, 21046, 20896, 20746, 20597, 20450,
+    20303, 20157, 20013, 19870, 19727
+};
+
+// Hybrid window for the log-gain predictor
+static const uint16_t g728_wnrg[NSBGSZ] = {
+     3026,  6025,  8973, 11845, 14615, 17261, 19759, 22088, 24228, 26162,
+    27872, 29344, 30565, 31525, 32216, 32631, 32767, 32625, 32203, 31506,
+    30540, 29461, 28420, 27416, 26448, 25514, 24613, 23743, 22905, 22096,
+    21315, 20562, 19836, 19135
+};
+
+// Values for bandwidth broadcasting
+static const uint16_t g728_facv[LPC] = {
+    16192, 16002, 15815, 15629, 15446, 15265, 15086, 14910, 14735, 14562,
+    14391, 14223, 14056, 13891, 13729, 13568, 13409, 13252, 13096, 12943,
+    12791, 12641, 12493, 12347, 12202, 12059, 11918, 11778, 11640, 11504,
+    11369, 11236, 11104, 10974, 10845, 10718, 10593, 10468, 10346, 10225,
+    10105,  9986,  9869,  9754,  9639,  9526,  9415,  9304,  9195,  9088
+};
+
+#endif /* AVCODEC_G728DATA_H */
diff --git a/libavcodec/g728dec.c b/libavcodec/g728dec.c
new file mode 100644
index 0000000000..f932a50f6c
--- /dev/null
+++ b/libavcodec/g728dec.c
@@ -0,0 +1,220 @@
+/*
+ * G.728 decoder
+ * Copyright (c) 2025 Peter Ross
+ *
+ * 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 "avcodec.h"
+#include "celp_filters.h"
+#include "codec_internal.h"
+#include "decode.h"
+#include "get_bits.h"
+#include "g728data.h"
+#include "lpc_functions.h"
+#include "ra288.h"
+#include "libavutil/float_dsp.h"
+#include "libavutil/mem.h"
+#include "libavutil/mem_internal.h"
+#include "libavutil/opt.h"
+#include "libavutil/thread.h"
+
+#define MAX_BACKWARD_FILTER_ORDER  LPC
+#define MAX_BACKWARD_FILTER_LEN    NFRSZ
+#define MAX_BACKWARD_FILTER_NONREC NONR
+#define ATTEN 0.75f
+#include "g728_template.c"
+
+#define LPCW 10 /* Perceptual weighting filter order */
+#define GOFF 32.0f /* Log-gain offset value */
+
+static float g728_gq_db[8];
+static float g728_y_db[128];
+static float g728_wnr_r[FFALIGN(NSBSZ,16)];
+static float g728_wnrg_r[FFALIGN(NSBGSZ, 16)];
+static float g728_facv_f[FFALIGN(LPC, 16)];
+
+static av_cold void g728_init_static_data(void)
+{
+    for(int i = 0; i < FF_ARRAY_ELEMS(amptable); i++)
+        g728_gq_db[i] = 10.0f*log10f(amptable[i] * amptable[i]);
+
+    for (int i = 0; i < FF_ARRAY_ELEMS(codetable); i++) {
+        float cby[IDIM];
+        for (int j = 0; j < IDIM; j++)
+            cby[j] = codetable[i][j] * (1.0f/(1<<11));
+        g728_y_db[i] = 10.0f*log10f(avpriv_scalarproduct_float_c(cby, cby, IDIM) / IDIM);
+    }
+
+    for (int i = 0; i < NSBSZ; i++)
+        g728_wnr_r[i] = g728_wnr[NSBSZ - 1 - i] * (1.0f/(1<<15));
+    for (int i = 0; i < NSBGSZ; i++)
+        g728_wnrg_r[i] = g728_wnrg[NSBGSZ - 1 - i] * (1.0f/(1<<15));
+    for (int i = 0; i < LPC; i++)
+        g728_facv_f[i] = g728_facv[i] * (1.0f/(1<<14));
+}
+
+typedef struct {
+    AVFloatDSPContext *fdsp;
+    int valid;
+    float a[LPC];
+    DECLARE_ALIGNED(32, float, sb)[NSBSZ];
+    DECLARE_ALIGNED(32, float, sbg)[NSBGSZ];
+    DECLARE_ALIGNED(32, float, gp)[FFALIGN(LPCLG, 16)];
+    DECLARE_ALIGNED(32, float, atmp)[FFALIGN(LPC, 16)];
+    float rexp[LPC + 1];
+    float rexpg[LPCLG + 1];
+    float r[LPC + 1];
+    float alpha;
+} G728Context;
+
+static av_cold int g728_decode_init(AVCodecContext *avctx)
+{
+    static AVOnce init_static_once = AV_ONCE_INIT;
+    G728Context *s = avctx->priv_data;
+
+    s->fdsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT);
+    if (!s->fdsp)
+        return AVERROR(ENOMEM);
+
+    s->gp[0] = -1.0f;
+    for (int i = 0; i < NUPDATE; i++)
+        s->sbg[NSBGSZ - 1 -i] = -GOFF;
+
+    avctx->sample_fmt = AV_SAMPLE_FMT_FLT;
+
+    av_channel_layout_uninit(&avctx->ch_layout);
+    avctx->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
+
+    ff_thread_once(&init_static_once, g728_init_static_data);
+    return 0;
+}
+
+static av_cold int g728_decode_close(AVCodecContext *avctx)
+{
+    G728Context *s = avctx->priv_data;
+    av_freep(&s->fdsp);
+    return 0;
+}
+
+static int hybrid_window(AVFloatDSPContext *fdsp,
+                         int order, int n, int non_rec, float *out,
+                         const float *hist, float *out2, const float *window)
+{
+    do_hybrid_window(fdsp->vector_fmul, order, n, non_rec, out, hist, out2, window);
+    return out[order] != 0.0f;
+}
+
+static void decode_frame(G728Context *s, GetBitContext *gb, float *dst)
+{
+    float *gstate = s->sbg + NSBGSZ - 2;
+
+    for (int idx = 0; idx < NUPDATE; idx++) {
+        DECLARE_ALIGNED(32, float, et)[IDIM];
+        float *statelpc = s->sb + NSBSZ - NFRSZ + idx*IDIM;
+        float gain, gain_db;
+        int is, ig;
+
+        gain_db = 0.0f;
+        for (int i = 0; i < LPCLG; i++)
+            gain_db -= s->gp[i] * gstate[-i];
+        gain_db = av_clipf(gain_db, -GOFF, 28.0f);
+
+        is = get_bits(gb, 7); // shape index
+        ig = get_bits(gb, 3); // gain index
+
+        gain = powf(10.0f, (gain_db + GOFF) * .05f) * amptable[ig] * (1.0f/(1<<11));
+        for (int i = 0; i < IDIM; i++)
+            et[i] = codetable[is][i] * gain;
+
+        ff_celp_lp_synthesis_filterf(statelpc, s->a, et, IDIM, LPC);
+
+        for (int i = 0; i < IDIM; i++) {
+            statelpc[i] = av_clipf(statelpc[i], -4095.0f, 4095.0f);
+            dst[idx*IDIM + i] = statelpc[i] * (1.0f/(1<<12));
+        }
+
+        gstate++;
+        *gstate = FFMAX(-GOFF, g728_gq_db[ig] + g728_y_db[is] + gain_db);
+
+        if (idx == 0) {
+            DECLARE_ALIGNED(32, float, gptmp)[FFALIGN(LPCLG, 16)];
+            if (s->valid && (s->valid = !compute_lpc_coefs(s->r + 1, LPCW, LPC, s->atmp, 0, 0, 1, &s->alpha))) {
+                s->fdsp->vector_fmul(s->atmp, s->atmp, g728_facv_f, FFALIGN(LPC, 16));
+            }
+            if (hybrid_window(s->fdsp, LPCLG, NUPDATE, NONRLG, s->r, s->sbg, s->rexpg, g728_wnrg_r) &&
+                    !compute_lpc_coefs(s->r, 0, LPCLG, gptmp, 0, 0, 1, &s->alpha)) {
+                s->fdsp->vector_fmul(s->gp, gptmp, gain_bw_tab, FFALIGN(LPCLG, 16));
+            }
+            memmove(s->sbg, s->sbg + NUPDATE, sizeof(float)*(LPCLG + NONRLG));
+            gstate = s->sbg + NSBGSZ - 1 - NUPDATE;
+        } else if (idx == 1) {
+            if (s->valid)
+                memcpy(s->a, s->atmp, sizeof(float)*LPC);
+        }
+    }
+
+    s->valid = 0;
+    if (hybrid_window(s->fdsp, LPC, NFRSZ, NONR, s->r, s->sb, s->rexp, g728_wnr_r)) {
+        s->valid = !compute_lpc_coefs(s->r, 0, LPCW, s->atmp, 0, 0, 1, &s->alpha);
+    }
+
+    memmove(s->sb, s->sb + NFRSZ, sizeof(float)*(LPC + NONR));
+}
+
+static int g728_decode_frame(AVCodecContext *avctx, AVFrame *frame,
+                            int *got_frame_ptr, AVPacket *avpkt)
+{
+    G728Context *s = avctx->priv_data;
+    GetBitContext gb;
+    int ret;
+    int nb_frames = avpkt->size / 5;
+
+    if (!nb_frames)
+        return AVERROR_INVALIDDATA;
+
+    if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)
+        return ret;
+
+#define SAMPLES_PER_FRAME 20
+
+    frame->nb_samples = nb_frames * SAMPLES_PER_FRAME;
+    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+        return ret;
+
+    for (int i = 0; i < nb_frames; i++)
+        decode_frame(s, &gb, (float *)frame->data[0] + i * 20);
+
+    *got_frame_ptr = 1;
+
+    return nb_frames * 5;
+}
+
+const FFCodec ff_g728_decoder = {
+    .p.name         = "g728",
+    CODEC_LONG_NAME("G.728)"),
+    .p.type         = AVMEDIA_TYPE_AUDIO,
+    .p.id           = AV_CODEC_ID_G728,
+    .priv_data_size = sizeof(G728Context),
+    .init           = g728_decode_init,
+    .close          = g728_decode_close,
+    FF_CODEC_DECODE_CB(g728_decode_frame),
+    .p.capabilities = AV_CODEC_CAP_CHANNEL_CONF |
+                      AV_CODEC_CAP_DR1,
+    .p.sample_fmts  = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLT,
+                                                      AV_SAMPLE_FMT_NONE },
+};
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index dd846b4ae9..58b29c4c9d 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -553,6 +553,7 @@ int av_get_bits_per_sample(enum AVCodecID codec_id)
     case AV_CODEC_ID_DFPWM:
         return 1;
     case AV_CODEC_ID_ADPCM_SBPRO_2:
+    case AV_CODEC_ID_G728:
         return 2;
     case AV_CODEC_ID_ADPCM_SBPRO_3:
         return 3;
-- 
2.47.2

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)

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