lavfi: add channelsplit audio filter.

1 files changed, 146 insertions, 0 deletions

diff --git a/libavfilter/af_channelsplit.c b/libavfilter/af_channelsplit.c
new file mode 100644
index 0000000000..c3e7ccfc69
--- /dev/null
+++ b/libavfilter/af_channelsplit.c
@@ -0,0 +1,146 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Channel split filter
+ *
+ * Split an audio stream into per-channel streams.
+ */
+
+#include "libavutil/audioconvert.h"
+#include "libavutil/opt.h"
+
+#include "audio.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+
+typedef struct ChannelSplitContext {
+    const AVClass *class;
+
+    uint64_t channel_layout;
+    char    *channel_layout_str;
+} ChannelSplitContext;
+
+#define OFFSET(x) offsetof(ChannelSplitContext, x)
+#define A AV_OPT_FLAG_AUDIO_PARAM
+static const AVOption options[] = {
+    { "channel_layout", "Input channel layout.", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, { .str = "stereo" }, .flags = A },
+    { NULL },
+};
+
+static const AVClass channelsplit_class = {
+    .class_name = "channelsplit filter",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+static int init(AVFilterContext *ctx, const char *arg, void *opaque)
+{
+    ChannelSplitContext *s = ctx->priv;
+    int nb_channels;
+    int ret = 0, i;
+
+    s->class = &channelsplit_class;
+    av_opt_set_defaults(s);
+    if ((ret = av_set_options_string(s, arg, "=", ":")) < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Error parsing options string '%s'.\n", arg);
+        return ret;
+    }
+    if (!(s->channel_layout = av_get_channel_layout(s->channel_layout_str))) {
+        av_log(ctx, AV_LOG_ERROR, "Error parsing channel layout '%s'.\n",
+               s->channel_layout_str);
+        ret = AVERROR(EINVAL);
+        goto fail;
+    }
+
+    nb_channels = av_get_channel_layout_nb_channels(s->channel_layout);
+    for (i = 0; i < nb_channels; i++) {
+        uint64_t channel = av_channel_layout_extract_channel(s->channel_layout, i);
+        AVFilterPad pad  = { 0 };
+
+        pad.type = AVMEDIA_TYPE_AUDIO;
+        pad.name = av_get_channel_name(channel);
+
+        ff_insert_outpad(ctx, i, &pad);
+    }
+
+fail:
+    av_opt_free(s);
+    return ret;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    ChannelSplitContext *s = ctx->priv;
+    AVFilterChannelLayouts *in_layouts = NULL;
+    int i;
+
+    ff_set_common_formats    (ctx, ff_planar_sample_fmts());
+    ff_set_common_samplerates(ctx, ff_all_samplerates());
+
+    ff_add_channel_layout(&in_layouts, s->channel_layout);
+    ff_channel_layouts_ref(in_layouts, &ctx->inputs[0]->out_channel_layouts);
+
+    for (i = 0; i < ctx->output_count; i++) {
+        AVFilterChannelLayouts *out_layouts = NULL;
+        uint64_t channel = av_channel_layout_extract_channel(s->channel_layout, i);
+
+        ff_add_channel_layout(&out_layouts, channel);
+        ff_channel_layouts_ref(out_layouts, &ctx->outputs[i]->in_channel_layouts);
+    }
+
+    return 0;
+}
+
+static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *buf)
+{
+    AVFilterContext *ctx = inlink->dst;
+    int i;
+
+    for (i = 0; i < ctx->output_count; i++) {
+        AVFilterBufferRef *buf_out = avfilter_ref_buffer(buf, ~AV_PERM_WRITE);
+
+        if (!buf_out)
+            return;
+
+        buf_out->data[0] = buf_out->extended_data[0] = buf_out->extended_data[i];
+        buf_out->audio->channel_layout =
+            av_channel_layout_extract_channel(buf->audio->channel_layout, i);
+
+        ff_filter_samples(ctx->outputs[i], buf_out);
+    }
+    avfilter_unref_buffer(buf);
+}
+
+AVFilter avfilter_af_channelsplit = {
+    .name           = "channelsplit",
+    .description    = NULL_IF_CONFIG_SMALL("Split audio into per-channel streams"),
+    .priv_size      = sizeof(ChannelSplitContext),
+
+    .init           = init,
+    .query_formats  = query_formats,
+
+    .inputs  = (const AVFilterPad[]){{ .name           = "default",
+                                       .type           = AVMEDIA_TYPE_AUDIO,
+                                       .filter_samples = filter_samples, },
+                                     { NULL }},
+    .outputs = (const AVFilterPad[]){{ NULL }},
+};