libavfilter/af_ambisonic.c | 139
+++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 139 insertions(+)
create mode 100644 libavfilter/af_ambisonic.c
diff --git a/libavfilter/af_ambisonic.c b/libavfilter/af_ambisonic.c
new file mode 100644
index 0000000..98b0e44
--- /dev/null
+++ b/libavfilter/af_ambisonic.c
@@ -0,0 +1,139 @@
+/*
+ * 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"
+
+#define root8 2.828
+
+typedef struct AmbisonicContext {
+ const AVClass *class;
+ /*Not needed, if any new variables are to be used, this struct can be
populated*/
+
+} AmbisonicContext;
+
+#define OFFSET(x) offsetof(AmbisonicContext, x) //Future use(maybe)
+
+static const AVOption ambisonic_options[] = { //square will be an option
+{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];
+ /*If variables used, this has to be created*/
+ // AmbisonicContext *s = ctx->priv;
+ // const float *src = (const float *)in->data[0];
+ // float *dst;
+ float *lf,*lb,*rb,*rf;
+ AVFrame *out;
+ int itr;
+ float *w,*x,*y;
+
+ 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);
+ }
+
+ /*If planar samples are used, output must be put in dst*/
+ //dst = (float *)out->data[0];
+
+ lf = (float *)malloc(sizeof(float));
+ lb = (float *)malloc(sizeof(float));
+ rb = (float *)malloc(sizeof(float));
+ rf = (float *)malloc(sizeof(float));
+
+ for(itr=0;itr<in->nb_samples;itr++)
+ {
+ *lf=0,*lb=0,*rb=0,*rf=0;
+ /*Float pointers to the samples*/
+ w=(float *)(*(in->extended_data)+itr);
+ x=(float *)(*(in->extended_data+1)+itr);
+ y=(float *)(*(in->extended_data+2)+itr);
+
+ *lf = root8 * (2*(*w)+*x+*y);
+ *lb = root8 * (2*(*w)-*x+*y);
+ *rb = root8 * (2*(*w)-*x-*y);
+ *rf = root8 * (2*(*w)+*x-*y);
+
+ /*Mathematical coefficients taken from :
https://en.wikipedia.org/wiki/Ambisonics*/
+ out->extended_data[0][itr]= *lf;
+ out->extended_data[1][itr]= *lb;
+ out->extended_data[2][itr]= *rb;
+ out->extended_data[3][itr]= *rf;
+ }
+
+ 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,
+ // .config_props = config_input,
+ },
+ { 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,
+ // .uninit = uninit,
+ .inputs = inputs,
+ .outputs = outputs,
+};
\ No newline at end of file
--
2.7.4
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