filter/hdcd: new filter plugin based on FFmpeg's "af_hdcd"

NEWS

@@ -1,6 +1,8 @@
 ver 0.22 (not yet released)
 * input
   - ffmpeg: allow partial reads
+* filter
+  - hdcd: new plugin based on FFmpeg's "af_hdcd" for HDCD playback
 
 ver 0.21.7 (not yet released)
 * require Meson 0.49.0 for native libgcrypt-config support

src/filter/FilterRegistry.cxx

@@ -22,6 +22,8 @@
 #include "plugins/NullFilterPlugin.hxx"
 #include "plugins/RouteFilterPlugin.hxx"
 #include "plugins/NormalizeFilterPlugin.hxx"
+#include "plugins/HdcdFilterPlugin.hxx"
+#include "config.h"
 
 #include <string.h>
 
@@ -29,6 +31,9 @@ static const FilterPlugin *const filter_plugins[] = {
 	&null_filter_plugin,
 	&route_filter_plugin,
 	&normalize_filter_plugin,
+#ifdef HAVE_LIBAVFILTER
+	&hdcd_filter_plugin,
+#endif
 	nullptr,
 };
 

src/filter/plugins/HdcdFilterPlugin.cxx

@@ -0,0 +1,160 @@
+/*
+ * Copyright 2003-2019 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "HdcdFilterPlugin.hxx"
+#include "filter/FilterPlugin.hxx"
+#include "filter/Filter.hxx"
+#include "filter/NullFilter.hxx"
+#include "filter/Prepared.hxx"
+#include "lib/ffmpeg/Filter.hxx"
+#include "lib/ffmpeg/Frame.hxx"
+#include "lib/ffmpeg/SampleFormat.hxx"
+#include "config/Block.hxx"
+#include "AudioFormat.hxx"
+#include "util/ConstBuffer.hxx"
+
+extern "C" {
+#include <libavfilter/buffersrc.h>
+#include <libavfilter/buffersink.h>
+}
+
+#include <string.h>
+
+static constexpr const char *hdcd_graph = "hdcd";
+
+gcc_pure
+static bool
+MaybeHdcd(const AudioFormat &audio_format) noexcept
+{
+	return audio_format.sample_rate == 44100 &&
+		audio_format.format == SampleFormat::S16 &&
+		audio_format.channels == 2;
+}
+
+class HdcdFilter final : public Filter {
+	Ffmpeg::FilterGraph graph;
+	Ffmpeg::FilterContext buffer_src, buffer_sink;
+	Ffmpeg::Frame frame, out_frame;
+
+	size_t in_audio_frame_size;
+	size_t out_audio_frame_size;
+
+public:
+	explicit HdcdFilter(AudioFormat &audio_format);
+
+	/* virtual methods from class Filter */
+	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+};
+
+inline
+HdcdFilter::HdcdFilter(AudioFormat &audio_format)
+	:Filter(audio_format)
+{
+	buffer_src = Ffmpeg::FilterContext::MakeAudioBufferSource(audio_format,
+								  *graph);
+
+	buffer_sink = Ffmpeg::FilterContext::MakeAudioBufferSink(*graph);
+
+	Ffmpeg::FilterInOut io_sink("out", *buffer_sink);
+	Ffmpeg::FilterInOut io_src("in", *buffer_src);
+	auto io = graph.Parse(hdcd_graph, std::move(io_sink),
+			      std::move(io_src));
+
+	if (io.first.get() != nullptr)
+		throw std::runtime_error("FFmpeg filter has an open input");
+
+	if (io.second.get() != nullptr)
+		throw std::runtime_error("FFmpeg filter has an open output");
+
+	graph.CheckAndConfigure();
+
+	frame->format = Ffmpeg::ToFfmpegSampleFormat(audio_format.format);
+	frame->sample_rate = audio_format.sample_rate;
+	frame->channels = audio_format.channels;
+
+	// TODO: convert to 32 bit only if HDCD actually detected
+	out_audio_format.format = SampleFormat::S32;
+
+	in_audio_frame_size = audio_format.GetFrameSize();
+	out_audio_frame_size = audio_format.GetFrameSize();
+}
+
+class PreparedHdcdFilter final : public PreparedFilter {
+public:
+	/* virtual methods from class PreparedFilter */
+	std::unique_ptr<Filter> Open(AudioFormat &af) override;
+};
+
+std::unique_ptr<Filter>
+PreparedHdcdFilter::Open(AudioFormat &audio_format)
+{
+	if (MaybeHdcd(audio_format))
+		return std::make_unique<HdcdFilter>(audio_format);
+	else
+		/* this cannot be HDCD, so let's copy as-is using
+		   NullFilter */
+		return std::make_unique<NullFilter>(audio_format);
+}
+
+ConstBuffer<void>
+HdcdFilter::FilterPCM(ConstBuffer<void> src)
+{
+	/* submit source data into the FFmpeg audio buffer source */
+
+	frame->nb_samples = src.size / in_audio_frame_size;
+
+	frame.GetBuffer();
+	frame.MakeWritable();
+
+	memcpy(frame.GetData(0), src.data, src.size);
+
+	int err = av_buffersrc_write_frame(buffer_src.get(), frame.get());
+	if (err < 0)
+		throw MakeFfmpegError(err, "av_buffersrc_write_frame() failed");
+
+	/* collect filtered data from the FFmpeg audio buffer sink */
+
+	err = av_buffersink_get_frame(buffer_sink.get(), out_frame.get());
+	if (err < 0) {
+		if (err == AVERROR(EAGAIN) || err == AVERROR_EOF)
+			return nullptr;
+
+		throw MakeFfmpegError(err, "av_buffersink_get_frame() failed");
+	}
+
+	/* TODO: call av_buffersink_get_frame() repeatedly?  Not
+	   possible with MPD's current Filter API */
+
+	return {out_frame.GetData(0), out_frame->nb_samples * GetOutAudioFormat().GetFrameSize()};
+}
+
+static std::unique_ptr<PreparedFilter>
+hdcd_filter_init(const ConfigBlock &)
+{
+	/* check if the graph can be parsed (and discard the
+	   object) */
+	Ffmpeg::FilterGraph().Parse(hdcd_graph);
+
+	return std::make_unique<PreparedHdcdFilter>();
+}
+
+const FilterPlugin hdcd_filter_plugin = {
+	"hdcd",
+	hdcd_filter_init,
+};

src/filter/plugins/HdcdFilterPlugin.hxx

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2003-2019 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_HDCD_FILTER_PLUGIN_HXX
+#define MPD_HDCD_FILTER_PLUGIN_HXX
+
+struct FilterPlugin;
+
+extern const FilterPlugin hdcd_filter_plugin;
+
+#endif

src/filter/plugins/meson.build

@@ -1,3 +1,13 @@
+filter_plugins_sources = []
+filter_plugins_deps = []
+
+if libavfilter_dep.found()
+  filter_plugins_sources += [
+    'HdcdFilterPlugin.cxx',
+  ]
+  filter_plugins_deps += ffmpeg_dep
+endif
+
 filter_plugins = static_library(
   'filter_plugins',
   '../../AudioCompress/compress.c',
@@ -9,6 +19,7 @@ filter_plugins = static_library(
   'NormalizeFilterPlugin.cxx',
   'ReplayGainFilterPlugin.cxx',
   'VolumeFilterPlugin.cxx',
+  filter_plugins_sources,
   include_directories: inc,
 )
 
@@ -18,5 +29,5 @@ filter_plugins_dep = declare_dependency(
     filter_api_dep,
     pcm_dep,
     config_dep,
-  ],
+  ] + filter_plugins_deps,
 )