Patch details:
File added avfilter/af_ambisonic.c
Entries made in avfilter/Makefile and avfilter/allfilters.c
Entry made in Changelog
On Sat, Mar 11, 2017 at 4:29 PM, Sanchit Sinha <sanchit15...@iiitd.ac.in>
wrote:
>
> Thanks Andy for the valuable info! It would be good to talk and learn from
> these guys, especially for an amateur like me. :)
>
> On Sat, Mar 11, 2017 at 4:23 PM, Andy Furniss <adf.li...@gmail.com> wrote:
>
>> Paul B Mahol wrote:
>>
>>> On 3/11/17, Andy Furniss <adf.li...@gmail.com> wrote:
>>>
>>>> Sanchit Sinha wrote:
>>>>
>>>>> libavfilter/af_ambisonic.c | 139
>>>>>
>>>>
>>>> + 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);
>>>>>
>>>>
>>>> Seems a bit misleading to call something ambisonic if all it will
>>>> do is 2d, so partial b-format to (square?) 4 channel.
>>>>
>>>> Why not be more specific in the name so the limitation is clear.
>>>>
>>>
>>> This is just for qualification task. Later filter willl be extended.
>>>
>>> It will not be applied as is in tree.
>>>
>>
>> Ahh, OK.
>>
>> A complicated subject.
>>
>> Sanchit, in case you don't know, some of the people who were around at
>> the birth of ambisonics, plus ambdec author can be found on the list -
>>
>> https://mail.music.vt.edu/mailman/listinfo/sursound
>>
>>
>>
>>
>>
>> _______________________________________________
>> ffmpeg-devel mailing list
>> ffmpeg-devel@ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>
>
>
>
> --
> Sanchit Sinha
> B.Tech- CSE
> IIIT-Delhi
> Roll-2015083
>
--
Sanchit Sinha
B.Tech- CSE
IIIT-Delhi
Roll-2015083
From bb9915658d1089e36f5b3131ec5851a058a57c62 Mon Sep 17 00:00:00 2001
From: Sanchit Sinha <sanchit15...@iiitd.ac.in>
Date: Sat, 11 Mar 2017 17:04:47 +0530
Subject: [PATCH] avfiler/af_ambisonic.c: file added avfilter/allfilters.c and
Makefile: entry added Changelog: entry mentioned
---
Changelog | 1 +
libavfilter/Makefile | 1 +
libavfilter/af_ambisonic.c | 137 +++++++++++++++++++++++++++++++++++++++++++++
libavfilter/allfilters.c | 1 +
4 files changed, 140 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..16fd612 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -47,6 +47,7 @@ OBJS-$(CONFIG_ALOOP_FILTER) += f_loop.o
OBJS-$(CONFIG_AMERGE_FILTER) += af_amerge.o
OBJS-$(CONFIG_AMETADATA_FILTER) += f_metadata.o
OBJS-$(CONFIG_AMIX_FILTER) += af_amix.o
+OBJS-$(CONFIG_AMBISONIC_FILTER) += af_ambisonic.o
OBJS-$(CONFIG_ANEQUALIZER_FILTER) += af_anequalizer.o
OBJS-$(CONFIG_ANULL_FILTER) += af_anull.o
OBJS-$(CONFIG_APAD_FILTER) += af_apad.o
diff --git a/libavfilter/af_ambisonic.c b/libavfilter/af_ambisonic.c
new file mode 100644
index 0000000..32f3c0c
--- /dev/null
+++ b/libavfilter/af_ambisonic.c
@@ -0,0 +1,137 @@
+/*
+ * 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;
+ /*Not needed, if any new variables are to be used, this struct can be populated(f)*/
+
+} AmbisonicContext;
+
+#define OFFSET(x) offsetof(AmbisonicContext, x)
+
+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;
+ AVFrame *out;
+ int itr;
+ float *w,*x,*y;
+ 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);
+ }
+
+ /*If planar samples are used, output must be put in dst*/
+ //dst = (float *)out->data[0];
+
+ w=(float *)in->extended_data[0];
+ x=(float *)in->extended_data[1];
+ y=(float *)in->extended_data[2];
+
+ for(itr=0;itr<in->nb_samples;itr++)
+ {
+ /*Float pointers to the samples*/
+
+ 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]);
+
+ 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
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index df1af8d..59aeb6d 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
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