@@ -14,6 +14,40 @@ Pass the audio source unchanged to the output.

 @c man end AUDIO FILTERS

+@chapter Audio Sources

+@c man begin AUDIO SOURCES

+

+Below is a description of the currently available audio sources.

+

+@section anullsrc

+

+Null audio source, never return audio frames. It is mainly useful as a

+template and to be employed in analysis / debugging tools.

+

+It accepts as optional parameter a string of the form

+@var{sample_rate}:@var{channel_layout}.

+

+@var{sample_rate} specify the sample rate, and defaults to 44100.

+

+@var{channel_layout} specify the channel layout, and can be either an

+integer or a string representing a channel layout. The default value

+of @var{channel_layout} is 3, which corresponds to CH_LAYOUT_STEREO.

+

+Check the channel_layout_map definition in

+@file{libavcodec/audioconvert.c} for the correspondance between string

+and channel layout values.

+

+Follow some examples:

+@example

+#  set the sample rate to 48000 Hz and the channel layout to CH_LAYOUT_MONO.

+anullsrc=48000:4

+

+# same as

+anullsrc=48000:mono

+@end example

+

+@c man end AUDIO SOURCES

+

 @chapter Video Filters

 @c man begin VIDEO FILTERS

@@ -16,6 +16,8 @@ OBJS = allfilters.o                                                     \

 OBJS-$(CONFIG_ANULL_FILTER)                  += af_anull.o

+OBJS-$(CONFIG_ANULLSRC_FILTER)               += asrc_anullsrc.o

+

 OBJS-$(CONFIG_ASPECT_FILTER)                 += vf_aspect.o

 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o

 OBJS-$(CONFIG_FIFO_FILTER)                   += vf_fifo.o

@@ -36,6 +36,8 @@ void avfilter_register_all(void)

     REGISTER_FILTER (ANULL,       anull,       af);

+    REGISTER_FILTER (ANULLSRC,    anullsrc,    asrc);

+

     REGISTER_FILTER (ASPECT,      aspect,      vf);

     REGISTER_FILTER (CROP,        crop,        vf);

     REGISTER_FILTER (FIFO,        fifo,        vf);

new file mode 100644

@@ -0,0 +1,96 @@

+/*

+ * 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

+ * null audio source

+ */

+

+#include "avfilter.h"

+#include "libavcodec/audioconvert.h"

+

+typedef struct {

+    int64_t channel_layout;

+    int64_t sample_rate;

+} ANullContext;

+

+static int init(AVFilterContext *ctx, const char *args, void *opaque)

+{

+    ANullContext *priv = ctx->priv;

+    char channel_layout_str[128] = "";

+

+    priv->sample_rate = 44100;

+    priv->channel_layout = CH_LAYOUT_STEREO;

+

+    if (args)

+        sscanf(args, "%"PRId64":%s", &priv->sample_rate, channel_layout_str);

+

+    if (priv->sample_rate < 0) {

+        av_log(ctx, AV_LOG_ERROR, "Invalid negative sample rate: %"PRId64"\n", priv->sample_rate);

+        return AVERROR(EINVAL);

+    }

+

+    if (*channel_layout_str)

+        if (!(priv->channel_layout = avcodec_get_channel_layout(channel_layout_str))

+            && sscanf(channel_layout_str, "%"PRId64, &priv->channel_layout) != 1) {

+            av_log(ctx, AV_LOG_ERROR, "Invalid value '%s' for channel layout\n",

+                   channel_layout_str);

+            return AVERROR(EINVAL);

+        }

+

+    return 0;

+}

+

+static int config_props(AVFilterLink *outlink)

+{

+    ANullContext *priv = outlink->src->priv;

+    char buf[128];

+    int chans_nb;

+

+    outlink->sample_rate = priv->sample_rate;

+    outlink->channel_layout = priv->channel_layout;

+

+    chans_nb = avcodec_channel_layout_num_channels(priv->channel_layout);

+    avcodec_get_channel_layout_string(buf, sizeof(buf), chans_nb, priv->channel_layout);

+    av_log(outlink->src, AV_LOG_INFO,

+           "sample_rate:%"PRId64 " channel_layout:%"PRId64 " channel_layout_description:'%s'\n",

+           priv->sample_rate, priv->channel_layout, buf);

+

+    return 0;

+}

+

+static int request_frame(AVFilterLink *link)

+{

+    return -1;

+}

+

+AVFilter avfilter_asrc_anullsrc = {

+    .name        = "anullsrc",

+    .description = NULL_IF_CONFIG_SMALL("Null audio source, never return audio frames."),

+

+    .init        = init,

+    .priv_size   = sizeof(ANullContext),

+

+    .inputs      = (AVFilterPad[]) {{ .name = NULL}},

+

+    .outputs     = (AVFilterPad[]) {{ .name = "default",

+                                      .type = AVMEDIA_TYPE_AUDIO,

+                                      .config_props = config_props,

+                                      .request_frame = request_frame, },

+                                    { .name = NULL}},

+};

@@ -25,7 +25,7 @@

 #include "libavutil/avutil.h"

 #define LIBAVFILTER_VERSION_MAJOR  1

-#define LIBAVFILTER_VERSION_MINOR 42

+#define LIBAVFILTER_VERSION_MINOR 43

 #define LIBAVFILTER_VERSION_MICRO  0

 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \