From 870baf207a74d3700954ba4c07a25f85a3730989 Mon Sep 17 00:00:00 2001
From: Sanchit Sinha <sanchit15083@iiitd.ac.in>
Date: Sat, 18 Mar 2017 15:11:50 +0530
Subject: [PATCH] added: lavf/af_ambisonic.c makefile allfilters.c changelog

Signed-off-by: Sanchit Sinha <sanchit15083@iiitd.ac.in>
---
 Changelog                  |   1 +
 libavfilter/Makefile       |   1 +
 libavfilter/af_ambisonic.c | 122 +++++++++++++++++++++++++++++++++++++++++++++
 libavfilter/allfilters.c   |   1 +
 4 files changed, 125 insertions(+)
 create mode 100644 libavfilter/af_ambisonic.c

diff --git a/Changelog b/Changelog
index 13628ca..b917ac2 100644
--- a/Changelog
+++ b/Changelog
@@ -26,6 +26,7 @@ version <next>:
 - native Opus encoder
 - ScreenPressor decoder
 - incomplete ClearVideo decoder
+- Ambisonic Decoder
 
 version 3.2:
 - libopenmpt demuxer
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 0ba1c74..4ebbd5a 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -44,6 +44,7 @@ OBJS-$(CONFIG_AINTERLEAVE_FILTER)            += f_interleave.o
 OBJS-$(CONFIG_ALIMITER_FILTER)               += af_alimiter.o
 OBJS-$(CONFIG_ALLPASS_FILTER)                += af_biquads.o
 OBJS-$(CONFIG_ALOOP_FILTER)                  += f_loop.o
+OBJS-$(CONFIG_AMBISONIC_FILTER)              += af_ambisonic.o
 OBJS-$(CONFIG_AMERGE_FILTER)                 += af_amerge.o
 OBJS-$(CONFIG_AMETADATA_FILTER)              += f_metadata.o
 OBJS-$(CONFIG_AMIX_FILTER)                   += af_amix.o
diff --git a/libavfilter/af_ambisonic.c b/libavfilter/af_ambisonic.c
new file mode 100644
index 0000000..7817bdc
--- /dev/null
+++ b/libavfilter/af_ambisonic.c
@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2017 Sanchit Sinha
+ * Copyright (c) 2017 Paul B Mahol
+ * 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 <stdio.h>
+#include "libavutil/avstring.h"
+#include "libavutil/channel_layout.h"
+#include "libavutil/opt.h"
+#include "audio.h"
+#include "avfilter.h"
+#include "formats.h"
+#include <math.h>
+
+typedef struct AmbisonicContext {
+    const AVClass *class;
+} AmbisonicContext;
+
+static const AVOption ambisonic_options[] = {
+    {NULL}
+};
+
+AVFILTER_DEFINE_CLASS(ambisonic);
+
+static int query_formats(AVFilterContext *ctx)
+{
+    AVFilterFormats *formats = NULL;
+    AVFilterChannelLayouts *layout = NULL;
+    int ret;
+
+    if ((ret = ff_add_format        (&formats, AV_SAMPLE_FMT_FLTP   )) < 0 ||
+        (ret = ff_set_common_formats              (ctx    , formats )) < 0 ||
+        (ret = ff_add_channel_layout (&layout , AV_CH_LAYOUT_4POINT0)) < 0 ||
+        (ret = ff_set_common_channel_layouts     (ctx    , layout   )) < 0)
+        return ret;
+
+    formats = ff_all_samplerates();
+    return ff_set_common_samplerates(ctx, formats);
+}
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    AVFrame *out;
+    int itr;
+    float *w,*x,*y,*c1,*c2,*c3,*c4;
+    float root8 = sqrt(8);
+    float lf=0,lb=0,rb=0,rf=0;
+
+    if (av_frame_is_writable(in)) {
+        out = in;
+    } else {
+        out = ff_get_audio_buffer(inlink, in->nb_samples);
+        if (!out){
+            av_frame_free(&in);
+            return AVERROR(ENOMEM);
+        }
+        av_frame_copy_props(out, in);
+    }
+
+    w=(float *)in->extended_data[0];
+    x=(float *)in->extended_data[1];
+    y=(float *)in->extended_data[2];
+    c1=(float *)out->extended_data[0];
+    c2=(float *)out->extended_data[1];
+    c3=(float *)out->extended_data[2];
+    c4=(float *)out->extended_data[3];
+
+    for(itr=0;itr<in->nb_samples;itr++){
+        lf = root8 * (2*(w[itr])+x[itr]+y[itr]);
+        lb = root8 * (2*(w[itr])-x[itr]+y[itr]);
+        rb = root8 * (2*(w[itr])-x[itr]-y[itr]);
+        rf = root8 * (2*(w[itr])+x[itr]-y[itr]);
+        c1[itr] = lf;
+        c2[itr] = rf;
+        c3[itr] = lb;
+        c4[itr] = rb;
+    }
+
+    if (out != in)
+        av_frame_free(&in);
+    return ff_filter_frame(outlink, out);
+}
+static const AVFilterPad inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_AUDIO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+static const AVFilterPad outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_AUDIO,
+    },
+    { NULL }
+};
+AVFilter ff_af_ambisonic = {
+    .name           = "ambisonic",
+    .description    = NULL_IF_CONFIG_SMALL("An ambisonic filter"),
+    .query_formats  = query_formats,
+    .priv_size      = sizeof(AmbisonicContext),
+    .priv_class     = &ambisonic_class,
+    .inputs         = inputs,
+    .outputs        = outputs,
+};
\ No newline at end of file
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index a262365..ca75c6c 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -56,6 +56,7 @@ static void register_all(void)
     REGISTER_FILTER(ALIMITER,       alimiter,       af);
     REGISTER_FILTER(ALLPASS,        allpass,        af);
     REGISTER_FILTER(ALOOP,          aloop,          af);
+    REGISTER_FILTER(AMBISONIC,      ambisonic,      af);
     REGISTER_FILTER(AMERGE,         amerge,         af);
     REGISTER_FILTER(AMETADATA,      ametadata,      af);
     REGISTER_FILTER(AMIX,           amix,           af);
-- 
2.7.4

