Add asrc_anullsrc - null audio source.

Based on a patch by "S.N. Hemanth Meenakshisundaram" smeenaks!ucsd!edu.

Originally committed as revision 25188 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 96 insertions, 0 deletions

diff --git a/libavfilter/asrc_anullsrc.c b/libavfilter/asrc_anullsrc.c
new file mode 100644
index 0000000000..e1c6480e2c
--- /dev/null
+++ b/libavfilter/asrc_anullsrc.c
@@ -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}},
+};