Fix GSM decoding: regular GSM and MSGSM do not use the same

bitstream endianness, so they cannot reuse the same code
without a lot of function call overhead.
Thus use templating to compile two different binaries.

Originally committed as revision 25312 to svn://svn.ffmpeg.org/ffmpeg/trunk

7 files changed, 362 insertions, 217 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 83aece2650..385ae027dd 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -136,8 +136,8 @@ OBJS-$(CONFIG_FRAPS_DECODER)           += fraps.o
 OBJS-$(CONFIG_FRWU_DECODER)            += frwu.o
 OBJS-$(CONFIG_GIF_DECODER)             += gifdec.o lzw.o
 OBJS-$(CONFIG_GIF_ENCODER)             += gif.o lzwenc.o
-OBJS-$(CONFIG_GSM_DECODER)             += gsmdec.o
-OBJS-$(CONFIG_GSM_MS_DECODER)          += gsmdec.o
+OBJS-$(CONFIG_GSM_DECODER)             += gsmdec.o gsmdec_data.o msgsmdec.o
+OBJS-$(CONFIG_GSM_MS_DECODER)          += gsmdec.o gsmdec_data.o msgsmdec.o
 OBJS-$(CONFIG_H261_DECODER)            += h261dec.o h261.o \
                                           mpegvideo.o error_resilience.o
 OBJS-$(CONFIG_H261_ENCODER)            += h261enc.o h261.o             \
diff --git a/libavcodec/gsmdec.c b/libavcodec/gsmdec.c
index a9d9c345e8..3b85504f37 100644
--- a/libavcodec/gsmdec.c
+++ b/libavcodec/gsmdec.c
@@ -24,26 +24,11 @@
  * GSM decoder
  */
 
-#define ALT_BITSTREAM_READER_LE
 #include "avcodec.h"
 #include "get_bits.h"
+#include "msgsmdec.h"
 
-// input and output sizes in byte
-#define GSM_BLOCK_SIZE    33
-#define GSM_MS_BLOCK_SIZE 65
-#define GSM_FRAME_SIZE   160
-
-typedef struct {
-    // Contains first 120 elements from the previous frame
-    // (used by long_term_synth according to the "lag"),
-    // then in the following 160 elements the current
-    // frame is constructed.
-    int16_t ref_buf[280];
-    int v[9];
-    int lar[2][8];
-    int lar_idx;
-    int msr;
-} GSMContext;
+#include "gsmdec_template.c"
 
 static av_cold int gsm_init(AVCodecContext *avctx)
 {
@@ -65,199 +50,6 @@ static av_cold int gsm_init(AVCodecContext *avctx)
     return 0;
 }
 
-static const int16_t dequant_tab[64][8] = {
-    {   -28,    -20,    -12,     -4,      4,     12,     20,     28},
-    {   -56,    -40,    -24,     -8,      8,     24,     40,     56},
-    {   -84,    -60,    -36,    -12,     12,     36,     60,     84},
-    {  -112,    -80,    -48,    -16,     16,     48,     80,    112},
-    {  -140,   -100,    -60,    -20,     20,     60,    100,    140},
-    {  -168,   -120,    -72,    -24,     24,     72,    120,    168},
-    {  -196,   -140,    -84,    -28,     28,     84,    140,    196},
-    {  -224,   -160,    -96,    -32,     32,     96,    160,    224},
-    {  -252,   -180,   -108,    -36,     36,    108,    180,    252},
-    {  -280,   -200,   -120,    -40,     40,    120,    200,    280},
-    {  -308,   -220,   -132,    -44,     44,    132,    220,    308},
-    {  -336,   -240,   -144,    -48,     48,    144,    240,    336},
-    {  -364,   -260,   -156,    -52,     52,    156,    260,    364},
-    {  -392,   -280,   -168,    -56,     56,    168,    280,    392},
-    {  -420,   -300,   -180,    -60,     60,    180,    300,    420},
-    {  -448,   -320,   -192,    -64,     64,    192,    320,    448},
-    {  -504,   -360,   -216,    -72,     72,    216,    360,    504},
-    {  -560,   -400,   -240,    -80,     80,    240,    400,    560},
-    {  -616,   -440,   -264,    -88,     88,    264,    440,    616},
-    {  -672,   -480,   -288,    -96,     96,    288,    480,    672},
-    {  -728,   -520,   -312,   -104,    104,    312,    520,    728},
-    {  -784,   -560,   -336,   -112,    112,    336,    560,    784},
-    {  -840,   -600,   -360,   -120,    120,    360,    600,    840},
-    {  -896,   -640,   -384,   -128,    128,    384,    640,    896},
-    { -1008,   -720,   -432,   -144,    144,    432,    720,   1008},
-    { -1120,   -800,   -480,   -160,    160,    480,    800,   1120},
-    { -1232,   -880,   -528,   -176,    176,    528,    880,   1232},
-    { -1344,   -960,   -576,   -192,    192,    576,    960,   1344},
-    { -1456,  -1040,   -624,   -208,    208,    624,   1040,   1456},
-    { -1568,  -1120,   -672,   -224,    224,    672,   1120,   1568},
-    { -1680,  -1200,   -720,   -240,    240,    720,   1200,   1680},
-    { -1792,  -1280,   -768,   -256,    256,    768,   1280,   1792},
-    { -2016,  -1440,   -864,   -288,    288,    864,   1440,   2016},
-    { -2240,  -1600,   -960,   -320,    320,    960,   1600,   2240},
-    { -2464,  -1760,  -1056,   -352,    352,   1056,   1760,   2464},
-    { -2688,  -1920,  -1152,   -384,    384,   1152,   1920,   2688},
-    { -2912,  -2080,  -1248,   -416,    416,   1248,   2080,   2912},
-    { -3136,  -2240,  -1344,   -448,    448,   1344,   2240,   3136},
-    { -3360,  -2400,  -1440,   -480,    480,   1440,   2400,   3360},
-    { -3584,  -2560,  -1536,   -512,    512,   1536,   2560,   3584},
-    { -4032,  -2880,  -1728,   -576,    576,   1728,   2880,   4032},
-    { -4480,  -3200,  -1920,   -640,    640,   1920,   3200,   4480},
-    { -4928,  -3520,  -2112,   -704,    704,   2112,   3520,   4928},
-    { -5376,  -3840,  -2304,   -768,    768,   2304,   3840,   5376},
-    { -5824,  -4160,  -2496,   -832,    832,   2496,   4160,   5824},
-    { -6272,  -4480,  -2688,   -896,    896,   2688,   4480,   6272},
-    { -6720,  -4800,  -2880,   -960,    960,   2880,   4800,   6720},
-    { -7168,  -5120,  -3072,  -1024,   1024,   3072,   5120,   7168},
-    { -8063,  -5759,  -3456,  -1152,   1152,   3456,   5760,   8064},
-    { -8959,  -6399,  -3840,  -1280,   1280,   3840,   6400,   8960},
-    { -9855,  -7039,  -4224,  -1408,   1408,   4224,   7040,   9856},
-    {-10751,  -7679,  -4608,  -1536,   1536,   4608,   7680,  10752},
-    {-11647,  -8319,  -4992,  -1664,   1664,   4992,   8320,  11648},
-    {-12543,  -8959,  -5376,  -1792,   1792,   5376,   8960,  12544},
-    {-13439,  -9599,  -5760,  -1920,   1920,   5760,   9600,  13440},
-    {-14335, -10239,  -6144,  -2048,   2048,   6144,  10240,  14336},
-    {-16127, -11519,  -6912,  -2304,   2304,   6912,  11519,  16127},
-    {-17919, -12799,  -7680,  -2560,   2560,   7680,  12799,  17919},
-    {-19711, -14079,  -8448,  -2816,   2816,   8448,  14079,  19711},
-    {-21503, -15359,  -9216,  -3072,   3072,   9216,  15359,  21503},
-    {-23295, -16639,  -9984,  -3328,   3328,   9984,  16639,  23295},
-    {-25087, -17919, -10752,  -3584,   3584,  10752,  17919,  25087},
-    {-26879, -19199, -11520,  -3840,   3840,  11520,  19199,  26879},
-    {-28671, -20479, -12288,  -4096,   4096,  12288,  20479,  28671}
-};
-
-static void apcm_dequant_add(GetBitContext *gb, int16_t *dst)
-{
-    int i;
-    int maxidx = get_bits(gb, 6);
-    const int16_t *tab = dequant_tab[maxidx];
-    for (i = 0; i < 13; i++)
-        dst[3*i] += tab[get_bits(gb, 3)];
-}
-
-static inline int gsm_mult(int a, int b)
-{
-    return (a * b + (1 << 14)) >> 15;
-}
-
-static const uint16_t long_term_gain_tab[4] = {
-    3277, 11469, 21299, 32767
-};
-
-static void long_term_synth(int16_t *dst, int lag, int gain_idx)
-{
-    int i;
-    const int16_t *src = dst - lag;
-    uint16_t gain = long_term_gain_tab[gain_idx];
-    for (i = 0; i < 40; i++)
-        dst[i] = gsm_mult(gain, src[i]);
-}
-
-static inline int decode_log_area(int coded, int factor, int offset)
-{
-    coded <<= 10;
-    coded -= offset;
-    return gsm_mult(coded, factor) << 1;
-}
-
-static av_noinline int get_rrp(int filtered)
-{
-    int abs = FFABS(filtered);
-    if      (abs < 11059) abs <<= 1;
-    else if (abs < 20070) abs += 11059;
-    else                  abs = (abs >> 2) + 26112;
-    return filtered < 0 ? -abs : abs;
-}
-
-static int filter_value(int in, int rrp[8], int v[9])
-{
-    int i;
-    for (i = 7; i >= 0; i--) {
-        in -= gsm_mult(rrp[i], v[i]);
-        v[i + 1] = v[i] + gsm_mult(rrp[i], in);
-    }
-    v[0] = in;
-    return in;
-}
-
-static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)
-{
-    int i;
-    int rrp[8];
-    int *lar = ctx->lar[ctx->lar_idx];
-    int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];
-    for (i = 0; i < 8; i++)
-        rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));
-    for (i = 0; i < 13; i++)
-        dst[i] = filter_value(src[i], rrp, ctx->v);
-
-    for (i = 0; i < 8; i++)
-        rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar     [i] >> 1));
-    for (i = 13; i < 27; i++)
-        dst[i] = filter_value(src[i], rrp, ctx->v);
-
-    for (i = 0; i < 8; i++)
-        rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar     [i] >> 1) + (lar[i] >> 2));
-    for (i = 27; i < 40; i++)
-        dst[i] = filter_value(src[i], rrp, ctx->v);
-
-    for (i = 0; i < 8; i++)
-        rrp[i] = get_rrp(lar[i]);
-    for (i = 40; i < 160; i++)
-        dst[i] = filter_value(src[i], rrp, ctx->v);
-
-    ctx->lar_idx ^= 1;
-}
-
-static int postprocess(int16_t *data, int msr)
-{
-    int i;
-    for (i = 0; i < 160; i++) {
-        msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));
-        data[i] = av_clip_int16(msr << 1) & ~7;
-    }
-    return msr;
-}
-
-static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,
-                            GetBitContext *gb)
-{
-    GSMContext *ctx = avctx->priv_data;
-    int i;
-    int16_t *ref_dst = ctx->ref_buf + 120;
-    int *lar = ctx->lar[ctx->lar_idx];
-    lar[0] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
-    lar[1] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
-    lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);
-    lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);
-    lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) +   94*2);
-    lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);
-    lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) -  341*2);
-    lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);
-
-    for (i = 0; i < 4; i++) {
-        int lag      = get_bits(gb, 7);
-        int gain_idx = get_bits(gb, 2);
-        int offset   = get_bits(gb, 2);
-        lag = av_clip(lag, 40, 120);
-        long_term_synth(ref_dst, lag, gain_idx);
-        apcm_dequant_add(gb, ref_dst + offset);
-        ref_dst += 40;
-    }
-    memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));
-    short_term_synth(ctx, samples, ctx->ref_buf + 120);
-    // for optimal speed this could be merged with short_term_synth,
-    // not done yet because it is a bit ugly
-    ctx->msr = postprocess(samples, ctx->msr);
-    return 0;
-}
-
 static int gsm_decode_frame(AVCodecContext *avctx, void *data,
                             int *data_size, AVPacket *avpkt)
 {
@@ -273,10 +65,10 @@ static int gsm_decode_frame(AVCodecContext *avctx, void *data,
     *data_size = 0;
     if(buf_size < avctx->block_align)
         return AVERROR_INVALIDDATA;
-    init_get_bits(&gb, buf, buf_size * 8);
 
     switch (avctx->codec_id) {
     case CODEC_ID_GSM:
+        init_get_bits(&gb, buf, buf_size * 8);
         if (get_bits(&gb, 4) != 0xd)
             av_log(avctx, AV_LOG_WARNING, "Missing GSM magic!\n");
         res = gsm_decode_block(avctx, samples, &gb);
@@ -284,10 +76,7 @@ static int gsm_decode_frame(AVCodecContext *avctx, void *data,
             return res;
         break;
     case CODEC_ID_GSM_MS:
-        res = gsm_decode_block(avctx, samples, &gb);
-        if (res < 0)
-            return res;
-        res = gsm_decode_block(avctx, samples + GSM_FRAME_SIZE, &gb);
+        res = ff_msgsm_decode_block(avctx, samples, buf);
         if (res < 0)
             return res;
     }
diff --git a/libavcodec/gsmdec_data.c b/libavcodec/gsmdec_data.c
new file mode 100644
index 0000000000..4324ea28a9
--- /dev/null
+++ b/libavcodec/gsmdec_data.c
@@ -0,0 +1,94 @@
+/*
+ * gsm 06.10 decoder data
+ * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
+ *
+ * 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 <stdint.h>
+#include "gsmdec_data.h"
+
+const uint16_t ff_gsm_long_term_gain_tab[4] = {
+    3277, 11469, 21299, 32767
+};
+
+const int16_t ff_gsm_dequant_tab[64][8] = {
+    {   -28,    -20,    -12,     -4,      4,     12,     20,     28},
+    {   -56,    -40,    -24,     -8,      8,     24,     40,     56},
+    {   -84,    -60,    -36,    -12,     12,     36,     60,     84},
+    {  -112,    -80,    -48,    -16,     16,     48,     80,    112},
+    {  -140,   -100,    -60,    -20,     20,     60,    100,    140},
+    {  -168,   -120,    -72,    -24,     24,     72,    120,    168},
+    {  -196,   -140,    -84,    -28,     28,     84,    140,    196},
+    {  -224,   -160,    -96,    -32,     32,     96,    160,    224},
+    {  -252,   -180,   -108,    -36,     36,    108,    180,    252},
+    {  -280,   -200,   -120,    -40,     40,    120,    200,    280},
+    {  -308,   -220,   -132,    -44,     44,    132,    220,    308},
+    {  -336,   -240,   -144,    -48,     48,    144,    240,    336},
+    {  -364,   -260,   -156,    -52,     52,    156,    260,    364},
+    {  -392,   -280,   -168,    -56,     56,    168,    280,    392},
+    {  -420,   -300,   -180,    -60,     60,    180,    300,    420},
+    {  -448,   -320,   -192,    -64,     64,    192,    320,    448},
+    {  -504,   -360,   -216,    -72,     72,    216,    360,    504},
+    {  -560,   -400,   -240,    -80,     80,    240,    400,    560},
+    {  -616,   -440,   -264,    -88,     88,    264,    440,    616},
+    {  -672,   -480,   -288,    -96,     96,    288,    480,    672},
+    {  -728,   -520,   -312,   -104,    104,    312,    520,    728},
+    {  -784,   -560,   -336,   -112,    112,    336,    560,    784},
+    {  -840,   -600,   -360,   -120,    120,    360,    600,    840},
+    {  -896,   -640,   -384,   -128,    128,    384,    640,    896},
+    { -1008,   -720,   -432,   -144,    144,    432,    720,   1008},
+    { -1120,   -800,   -480,   -160,    160,    480,    800,   1120},
+    { -1232,   -880,   -528,   -176,    176,    528,    880,   1232},
+    { -1344,   -960,   -576,   -192,    192,    576,    960,   1344},
+    { -1456,  -1040,   -624,   -208,    208,    624,   1040,   1456},
+    { -1568,  -1120,   -672,   -224,    224,    672,   1120,   1568},
+    { -1680,  -1200,   -720,   -240,    240,    720,   1200,   1680},
+    { -1792,  -1280,   -768,   -256,    256,    768,   1280,   1792},
+    { -2016,  -1440,   -864,   -288,    288,    864,   1440,   2016},
+    { -2240,  -1600,   -960,   -320,    320,    960,   1600,   2240},
+    { -2464,  -1760,  -1056,   -352,    352,   1056,   1760,   2464},
+    { -2688,  -1920,  -1152,   -384,    384,   1152,   1920,   2688},
+    { -2912,  -2080,  -1248,   -416,    416,   1248,   2080,   2912},
+    { -3136,  -2240,  -1344,   -448,    448,   1344,   2240,   3136},
+    { -3360,  -2400,  -1440,   -480,    480,   1440,   2400,   3360},
+    { -3584,  -2560,  -1536,   -512,    512,   1536,   2560,   3584},
+    { -4032,  -2880,  -1728,   -576,    576,   1728,   2880,   4032},
+    { -4480,  -3200,  -1920,   -640,    640,   1920,   3200,   4480},
+    { -4928,  -3520,  -2112,   -704,    704,   2112,   3520,   4928},
+    { -5376,  -3840,  -2304,   -768,    768,   2304,   3840,   5376},
+    { -5824,  -4160,  -2496,   -832,    832,   2496,   4160,   5824},
+    { -6272,  -4480,  -2688,   -896,    896,   2688,   4480,   6272},
+    { -6720,  -4800,  -2880,   -960,    960,   2880,   4800,   6720},
+    { -7168,  -5120,  -3072,  -1024,   1024,   3072,   5120,   7168},
+    { -8063,  -5759,  -3456,  -1152,   1152,   3456,   5760,   8064},
+    { -8959,  -6399,  -3840,  -1280,   1280,   3840,   6400,   8960},
+    { -9855,  -7039,  -4224,  -1408,   1408,   4224,   7040,   9856},
+    {-10751,  -7679,  -4608,  -1536,   1536,   4608,   7680,  10752},
+    {-11647,  -8319,  -4992,  -1664,   1664,   4992,   8320,  11648},
+    {-12543,  -8959,  -5376,  -1792,   1792,   5376,   8960,  12544},
+    {-13439,  -9599,  -5760,  -1920,   1920,   5760,   9600,  13440},
+    {-14335, -10239,  -6144,  -2048,   2048,   6144,  10240,  14336},
+    {-16127, -11519,  -6912,  -2304,   2304,   6912,  11519,  16127},
+    {-17919, -12799,  -7680,  -2560,   2560,   7680,  12799,  17919},
+    {-19711, -14079,  -8448,  -2816,   2816,   8448,  14079,  19711},
+    {-21503, -15359,  -9216,  -3072,   3072,   9216,  15359,  21503},
+    {-23295, -16639,  -9984,  -3328,   3328,   9984,  16639,  23295},
+    {-25087, -17919, -10752,  -3584,   3584,  10752,  17919,  25087},
+    {-26879, -19199, -11520,  -3840,   3840,  11520,  19199,  26879},
+    {-28671, -20479, -12288,  -4096,   4096,  12288,  20479,  28671}
+};
diff --git a/libavcodec/gsmdec_data.h b/libavcodec/gsmdec_data.h
new file mode 100644
index 0000000000..6b05bf6c97
--- /dev/null
+++ b/libavcodec/gsmdec_data.h
@@ -0,0 +1,47 @@
+/*
+ * gsm 06.10 decoder data
+ * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
+ *
+ * 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 GSMDEC_DATA
+#define GSMDEC_DATA
+
+#include <stdint.h>
+
+// input and output sizes in byte
+#define GSM_BLOCK_SIZE    33
+#define GSM_MS_BLOCK_SIZE 65
+#define GSM_FRAME_SIZE   160
+
+typedef struct {
+    // Contains first 120 elements from the previous frame
+    // (used by long_term_synth according to the "lag"),
+    // then in the following 160 elements the current
+    // frame is constructed.
+    int16_t ref_buf[280];
+    int v[9];
+    int lar[2][8];
+    int lar_idx;
+    int msr;
+} GSMContext;
+
+extern const uint16_t ff_gsm_long_term_gain_tab[4];
+extern const int16_t ff_gsm_dequant_tab[64][8];
+
+#endif
diff --git a/libavcodec/gsmdec_template.c b/libavcodec/gsmdec_template.c
new file mode 100644
index 0000000000..b63ec9ed27
--- /dev/null
+++ b/libavcodec/gsmdec_template.c
@@ -0,0 +1,150 @@
+/*
+ * gsm 06.10 decoder
+ * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * GSM decoder
+ */
+
+#include "get_bits.h"
+#include "gsmdec_data.h"
+
+static void apcm_dequant_add(GetBitContext *gb, int16_t *dst)
+{
+    int i;
+    int maxidx = get_bits(gb, 6);
+    const int16_t *tab = ff_gsm_dequant_tab[maxidx];
+    for (i = 0; i < 13; i++)
+        dst[3*i] += tab[get_bits(gb, 3)];
+}
+
+static inline int gsm_mult(int a, int b)
+{
+    return (a * b + (1 << 14)) >> 15;
+}
+
+static void long_term_synth(int16_t *dst, int lag, int gain_idx)
+{
+    int i;
+    const int16_t *src = dst - lag;
+    uint16_t gain = ff_gsm_long_term_gain_tab[gain_idx];
+    for (i = 0; i < 40; i++)
+        dst[i] = gsm_mult(gain, src[i]);
+}
+
+static inline int decode_log_area(int coded, int factor, int offset)
+{
+    coded <<= 10;
+    coded -= offset;
+    return gsm_mult(coded, factor) << 1;
+}
+
+static av_noinline int get_rrp(int filtered)
+{
+    int abs = FFABS(filtered);
+    if      (abs < 11059) abs <<= 1;
+    else if (abs < 20070) abs += 11059;
+    else                  abs = (abs >> 2) + 26112;
+    return filtered < 0 ? -abs : abs;
+}
+
+static int filter_value(int in, int rrp[8], int v[9])
+{
+    int i;
+    for (i = 7; i >= 0; i--) {
+        in -= gsm_mult(rrp[i], v[i]);
+        v[i + 1] = v[i] + gsm_mult(rrp[i], in);
+    }
+    v[0] = in;
+    return in;
+}
+
+static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)
+{
+    int i;
+    int rrp[8];
+    int *lar = ctx->lar[ctx->lar_idx];
+    int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];
+    for (i = 0; i < 8; i++)
+        rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));
+    for (i = 0; i < 13; i++)
+        dst[i] = filter_value(src[i], rrp, ctx->v);
+
+    for (i = 0; i < 8; i++)
+        rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar     [i] >> 1));
+    for (i = 13; i < 27; i++)
+        dst[i] = filter_value(src[i], rrp, ctx->v);
+
+    for (i = 0; i < 8; i++)
+        rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar     [i] >> 1) + (lar[i] >> 2));
+    for (i = 27; i < 40; i++)
+        dst[i] = filter_value(src[i], rrp, ctx->v);
+
+    for (i = 0; i < 8; i++)
+        rrp[i] = get_rrp(lar[i]);
+    for (i = 40; i < 160; i++)
+        dst[i] = filter_value(src[i], rrp, ctx->v);
+
+    ctx->lar_idx ^= 1;
+}
+
+static int postprocess(int16_t *data, int msr)
+{
+    int i;
+    for (i = 0; i < 160; i++) {
+        msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));
+        data[i] = av_clip_int16(msr << 1) & ~7;
+    }
+    return msr;
+}
+
+static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,
+                            GetBitContext *gb)
+{
+    GSMContext *ctx = avctx->priv_data;
+    int i;
+    int16_t *ref_dst = ctx->ref_buf + 120;
+    int *lar = ctx->lar[ctx->lar_idx];
+    lar[0] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
+    lar[1] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
+    lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);
+    lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);
+    lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) +   94*2);
+    lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);
+    lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) -  341*2);
+    lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);
+
+    for (i = 0; i < 4; i++) {
+        int lag      = get_bits(gb, 7);
+        int gain_idx = get_bits(gb, 2);
+        int offset   = get_bits(gb, 2);
+        lag = av_clip(lag, 40, 120);
+        long_term_synth(ref_dst, lag, gain_idx);
+        apcm_dequant_add(gb, ref_dst + offset);
+        ref_dst += 40;
+    }
+    memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));
+    short_term_synth(ctx, samples, ctx->ref_buf + 120);
+    // for optimal speed this could be merged with short_term_synth,
+    // not done yet because it is a bit ugly
+    ctx->msr = postprocess(samples, ctx->msr);
+    return 0;
+}
diff --git a/libavcodec/msgsmdec.c b/libavcodec/msgsmdec.c
new file mode 100644
index 0000000000..e759451c83
--- /dev/null
+++ b/libavcodec/msgsmdec.c
@@ -0,0 +1,37 @@
+/*
+ * gsm 06.10 decoder, Microsoft variant
+ * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
+ *
+ * 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
+ */
+
+#define ALT_BITSTREAM_READER_LE
+#include "avcodec.h"
+#include "msgsmdec.h"
+#include "gsmdec_template.c"
+
+int ff_msgsm_decode_block(AVCodecContext *avctx, int16_t *samples,
+                          const uint8_t *buf)
+{
+    int res;
+    GetBitContext gb;
+    init_get_bits(&gb, buf, GSM_MS_BLOCK_SIZE * 8);
+    res = gsm_decode_block(avctx, samples, &gb);
+    if (res < 0)
+        return res;
+    return gsm_decode_block(avctx, samples + GSM_FRAME_SIZE, &gb);
+}
diff --git a/libavcodec/msgsmdec.h b/libavcodec/msgsmdec.h
new file mode 100644
index 0000000000..554edbcb6e
--- /dev/null
+++ b/libavcodec/msgsmdec.h
@@ -0,0 +1,28 @@
+/*
+ * gsm 06.10 decoder, Microsoft variant
+ * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
+ *
+ * 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 MSGSMDEC_H
+#define MSGSMDEC_H
+
+int ff_msgsm_decode_block(AVCodecContext *avctx, int16_t *samples,
+                          const uint8_t *buf);
+
+#endif