Merge tag 'v0.22.11'

NEWS

@@ -17,6 +17,17 @@ ver 0.23 (not yet released)
   - new tags "ComposerSort", "Ensemble", "Movement", "MovementNumber", and "Location"
 * new build-time dependency: libfmt
 
+ver 0.22.11 (2021/08/24)
+* protocol
+  - fix "albumart" crash
+* filter
+  - ffmpeg: pass "channel_layout" instead of "channels" to buffersrc
+  - ffmpeg: fix "av_buffersink_get_frame() failed: Resource temporarily unavailable"
+  - ffmpeg: support double-precision samples (by converting to single precision)
+* Android
+  - build with NDK r23
+  - playlist_directory defaults to "/sdcard/Android/data/org.musicpd/files/playlists"
+
 ver 0.22.10 (2021/08/06)
 * protocol
   - support "albumart" for virtual tracks in CUE sheets

android/AndroidManifest.xml

@@ -2,8 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           package="org.musicpd"
           android:installLocation="auto"
-          android:versionCode="58"
-          android:versionName="0.22.10">
+          android:versionCode="59"
+          android:versionName="0.22.11">
 
   <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="29"/>
 

android/build.py

@@ -24,15 +24,13 @@ android_abis = {
     'armeabi-v7a': {
         'arch': 'arm-linux-androideabi',
         'ndk_arch': 'arm',
-        'toolchain_arch': 'arm-linux-androideabi',
         'llvm_triple': 'armv7-linux-androideabi',
-        'cflags': '-fpic -march=armv7-a -mfpu=vfpv3-d16 -mfloat-abi=softfp',
+        'cflags': '-fpic -mfpu=neon -mfloat-abi=softfp',
     },
 
     'arm64-v8a': {
         'arch': 'aarch64-linux-android',
         'ndk_arch': 'arm64',
-        'toolchain_arch': 'aarch64-linux-android',
         'llvm_triple': 'aarch64-linux-android',
         'cflags': '-fpic',
     },
@@ -40,7 +38,6 @@ android_abis = {
     'x86': {
         'arch': 'i686-linux-android',
         'ndk_arch': 'x86',
-        'toolchain_arch': 'x86',
         'llvm_triple': 'i686-linux-android',
         'cflags': '-fPIC -march=i686 -mtune=intel -mssse3 -mfpmath=sse -m32',
     },
@@ -48,7 +45,6 @@ android_abis = {
     'x86_64': {
         'arch': 'x86_64-linux-android',
         'ndk_arch': 'x86_64',
-        'toolchain_arch': 'x86_64',
         'llvm_triple': 'x86_64-linux-android',
         'cflags': '-fPIC -m64',
     },
@@ -84,37 +80,28 @@ class AndroidNdkToolchain:
         ndk_arch = abi_info['ndk_arch']
         android_api_level = '21'
 
-        # select the NDK compiler
-        gcc_version = '4.9'
-
         install_prefix = os.path.join(arch_path, 'root')
 
         self.arch = arch
         self.install_prefix = install_prefix
-        self.toolchain_arch = abi_info['toolchain_arch']
 
-        toolchain_path = os.path.join(ndk_path, 'toolchains', self.toolchain_arch + '-' + gcc_version, 'prebuilt', build_arch)
         llvm_path = os.path.join(ndk_path, 'toolchains', 'llvm', 'prebuilt', build_arch)
         llvm_triple = abi_info['llvm_triple'] + android_api_level
 
         common_flags = '-Os -g'
         common_flags += ' ' + abi_info['cflags']
 
-        toolchain_bin = os.path.join(toolchain_path, 'bin')
         llvm_bin = os.path.join(llvm_path, 'bin')
         self.cc = os.path.join(llvm_bin, 'clang')
         self.cxx = os.path.join(llvm_bin, 'clang++')
-        common_flags += ' -target ' + llvm_triple + ' -gcc-toolchain ' + toolchain_path
+        common_flags += ' -target ' + llvm_triple
 
         common_flags += ' -fvisibility=hidden -fdata-sections -ffunction-sections'
 
-        # required flags from https://android.googlesource.com/platform/ndk/+/ndk-release-r20/docs/BuildSystemMaintainers.md#additional-required-arguments
-        common_flags += ' -fno-addrsig'
-
-        self.ar = os.path.join(toolchain_bin, arch + '-ar')
-        self.ranlib = os.path.join(toolchain_bin, arch + '-ranlib')
-        self.nm = os.path.join(toolchain_bin, arch + '-nm')
-        self.strip = os.path.join(toolchain_bin, arch + '-strip')
+        self.ar = os.path.join(llvm_bin, 'llvm-ar')
+        self.ranlib = os.path.join(llvm_bin, 'llvm-ranlib')
+        self.nm = os.path.join(llvm_bin, 'llvm-nm')
+        self.strip = os.path.join(llvm_bin, 'llvm-strip')
 
         self.cflags = common_flags
         self.cxxflags = common_flags

doc/user.rst

@@ -177,7 +177,7 @@ Compiling for Android
 You need:
 
 * Android SDK
-* `Android NDK r22 <https://developer.android.com/ndk/downloads>`_
+* `Android NDK r23 <https://developer.android.com/ndk/downloads>`_
 * `Meson 0.49.0 <http://mesonbuild.com/>`__ and `Ninja
   <https://ninja-build.org/>`__
 * cmake

python/build/openssl.py

@@ -48,7 +48,6 @@ class OpenSSLProject(MakeProject):
         }
 
         openssl_arch = openssl_archs[toolchain.arch]
-        cross_compile_prefix = toolchain.toolchain_arch + '-'
 
         subprocess.check_call(['./Configure',
                                'no-shared',
@@ -57,7 +56,6 @@ class OpenSSLProject(MakeProject):
                                'no-tests',
                                'no-asm', # "asm" causes build failures on Windows
                                openssl_arch,
-                               '--cross-compile-prefix=' + cross_compile_prefix,
                                '--prefix=' + toolchain.install_prefix],
                               cwd=src, env=toolchain.env)
         MakeProject.build(self, toolchain, src)

src/Main.cxx

@@ -158,7 +158,17 @@ glue_daemonize_init(const struct options *options,
 static void
 glue_mapper_init(const ConfigData &config)
 {
-	mapper_init(config.GetPath(ConfigOption::PLAYLIST_DIR));
+	auto playlist_directory = config.GetPath(ConfigOption::PLAYLIST_DIR);
+
+#ifdef ANDROID
+	/* if there is no explicit configuration, store playlists in
+	   "/sdcard/Android/data/org.musicpd/files/playlists" */
+	if (playlist_directory.IsNull())
+		playlist_directory = context->GetExternalFilesDir(Java::GetEnv(),
+								  "playlists");
+#endif
+
+	mapper_init(std::move(playlist_directory));
 }
 
 #ifdef ENABLE_DATABASE

src/android/Context.cxx

@@ -27,6 +27,25 @@
 #include "AudioManager.hxx"
 
 AllocatedPath
+Context::GetExternalFilesDir(JNIEnv *env, const char *_type) noexcept
+{
+	assert(_type != nullptr);
+
+	Java::Class cls{env, env->GetObjectClass(Get())};
+	jmethodID method = env->GetMethodID(cls, "getExternalFilesDir",
+					    "(Ljava/lang/String;)Ljava/io/File;");
+	assert(method);
+
+	Java::String type{env, _type};
+
+	jobject file = env->CallObjectMethod(Get(), method, type.Get());
+	if (Java::DiscardException(env) || file == nullptr)
+		return nullptr;
+
+	return Java::File::ToAbsolutePath(env, file);
+}
+
+AllocatedPath
 Context::GetCacheDir(JNIEnv *env) const noexcept
 {
 	assert(env != nullptr);

src/android/Context.hxx

@@ -30,10 +30,14 @@ public:
 	Context(JNIEnv *env, jobject obj) noexcept
 		:Java::GlobalObject(env, obj) {}
 
-	gcc_pure
+	[[gnu::pure]]
+	AllocatedPath GetExternalFilesDir(JNIEnv *env,
+					  const char *type) noexcept;
+
+	[[gnu::pure]]
 	AllocatedPath GetCacheDir(JNIEnv *env) const noexcept;
 
-	gcc_pure
+	[[gnu::pure]]
 	AudioManager *GetAudioManager(JNIEnv *env) noexcept;
 };
 

src/android/Environment.hxx

@@ -33,10 +33,10 @@ namespace Environment {
 	/**
 	 * Determine the mount point of the external SD card.
 	 */
-	gcc_pure
+	[[gnu::pure]]
 	AllocatedPath getExternalStorageDirectory() noexcept;
 
-	gcc_pure
+	[[gnu::pure]]
 	AllocatedPath getExternalStoragePublicDirectory(const char *type) noexcept;
 }
 

src/command/FileCommands.cxx

@@ -251,6 +251,9 @@ try {
 
 	AtScopeExit(db, song) { db->ReturnSong(song); };
 
+	if (song->real_uri == nullptr)
+		return directory_uri;
+
 	const char *real_uri = song->real_uri;
 
 	/* this is a simplification which is just enough for CUE

src/filter/plugins/FfmpegFilter.cxx

@@ -32,12 +32,12 @@ extern "C" {
 FfmpegFilter::FfmpegFilter(const AudioFormat &in_audio_format,
 			   const AudioFormat &_out_audio_format,
 			   Ffmpeg::FilterGraph &&_graph,
-			   Ffmpeg::FilterContext &&_buffer_src,
-			   Ffmpeg::FilterContext &&_buffer_sink) noexcept
+			   AVFilterContext &_buffer_src,
+			   AVFilterContext &_buffer_sink) noexcept
 	:Filter(_out_audio_format),
 	 graph(std::move(_graph)),
-	 buffer_src(std::move(_buffer_src)),
-	 buffer_sink(std::move(_buffer_sink)),
+	 buffer_src(_buffer_src),
+	 buffer_sink(_buffer_sink),
 	 in_format(Ffmpeg::ToFfmpegSampleFormat(in_audio_format.format)),
 	 in_sample_rate(in_audio_format.sample_rate),
 	 in_channels(in_audio_format.channels),
@@ -61,7 +61,7 @@ FfmpegFilter::FilterPCM(ConstBuffer<void> src)
 
 	memcpy(frame.GetData(0), src.data, src.size);
 
-	int err = av_buffersrc_add_frame(buffer_src.get(), frame.get());
+	int err = av_buffersrc_add_frame(&buffer_src, frame.get());
 	if (err < 0)
 		throw MakeFfmpegError(err, "av_buffersrc_write_frame() failed");
 
@@ -69,7 +69,7 @@ FfmpegFilter::FilterPCM(ConstBuffer<void> src)
 
 	frame.Unref();
 
-	err = av_buffersink_get_frame(buffer_sink.get(), frame.get());
+	err = av_buffersink_get_frame(&buffer_sink, frame.get());
 	if (err < 0) {
 		if (err == AVERROR(EAGAIN) || err == AVERROR_EOF)
 			return nullptr;

src/filter/plugins/FfmpegFilter.hxx

@@ -30,7 +30,7 @@
  */
 class FfmpegFilter final : public Filter {
 	Ffmpeg::FilterGraph graph;
-	Ffmpeg::FilterContext buffer_src, buffer_sink;
+	AVFilterContext &buffer_src, &buffer_sink;
 	Ffmpeg::Frame frame;
 
 	FfmpegBuffer interleave_buffer;
@@ -51,8 +51,8 @@ public:
 	FfmpegFilter(const AudioFormat &in_audio_format,
 		     const AudioFormat &_out_audio_format,
 		     Ffmpeg::FilterGraph &&_graph,
-		     Ffmpeg::FilterContext &&_buffer_src,
-		     Ffmpeg::FilterContext &&_buffer_sink) noexcept;
+		     AVFilterContext &_buffer_src,
+		     AVFilterContext &_buffer_sink) noexcept;
 
 	/* virtual methods from class Filter */
 	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;

src/filter/plugins/FfmpegFilterPlugin.cxx

@@ -37,39 +37,79 @@ public:
 	std::unique_ptr<Filter> Open(AudioFormat &af) override;
 };
 
+/**
+ * Fallback for PreparedFfmpegFilter::Open() just in case the filter's
+ * native output format could not be determined.
+ *
+ * TODO: improve the MPD filter API to allow returning the output
+ * format later, and eliminate this kludge
+ */
+static auto
+OpenWithAformat(const char *graph_string, AudioFormat &in_audio_format)
+{
+	Ffmpeg::FilterGraph graph;
+
+	auto &buffer_src =
+		Ffmpeg::MakeAudioBufferSource(in_audio_format, *graph);
+
+	auto &buffer_sink = Ffmpeg::MakeAudioBufferSink(*graph);
+
+	AudioFormat out_audio_format = in_audio_format;
+	auto &aformat = Ffmpeg::MakeAformat(out_audio_format, *graph);
+
+	int error = avfilter_link(&aformat, 0, &buffer_sink, 0);
+	if (error < 0)
+		throw MakeFfmpegError(error, "avfilter_link() failed");
+
+	graph.ParseSingleInOut(graph_string, aformat, buffer_src);
+	graph.CheckAndConfigure();
+
+	return std::make_unique<FfmpegFilter>(in_audio_format,
+					      out_audio_format,
+					      std::move(graph),
+					      buffer_src,
+					      buffer_sink);
+}
+
 std::unique_ptr<Filter>
 PreparedFfmpegFilter::Open(AudioFormat &in_audio_format)
 {
 	Ffmpeg::FilterGraph graph;
 
-	auto buffer_src =
-		Ffmpeg::FilterContext::MakeAudioBufferSource(in_audio_format,
-							     *graph);
+	auto &buffer_src =
+		Ffmpeg::MakeAudioBufferSource(in_audio_format, *graph);
 
-	auto buffer_sink = Ffmpeg::FilterContext::MakeAudioBufferSink(*graph);
+	auto &buffer_sink = Ffmpeg::MakeAudioBufferSink(*graph);
 
-	Ffmpeg::FilterInOut io_sink("out", *buffer_sink);
-	Ffmpeg::FilterInOut io_src("in", *buffer_src);
-	auto io = graph.Parse(graph_string, std::move(io_sink),
-			      std::move(io_src));
+	/* if the filter's output format is not supported by MPD, this
+	   "aformat" filter is inserted at the end and takes care for
+	   the required conversion */
+	auto &aformat = Ffmpeg::MakeAutoAformat(*graph);
 
-	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");
+	int error = avfilter_link(&aformat, 0, &buffer_sink, 0);
+	if (error < 0)
+		throw MakeFfmpegError(error, "avfilter_link() failed");
 
+	graph.ParseSingleInOut(graph_string, aformat, buffer_src);
 	graph.CheckAndConfigure();
 
 	const auto out_audio_format =
-		Ffmpeg::DetectFilterOutputFormat(in_audio_format, *buffer_src,
-						 *buffer_sink);
+		Ffmpeg::DetectFilterOutputFormat(in_audio_format, buffer_src,
+						 buffer_sink);
+
+	if (!out_audio_format.IsDefined())
+		/* the filter's native output format could not be
+		   determined yet, but we need to know it now; as a
+		   workaround for this MPD API deficiency, try again
+		   with an "aformat" filter which forces a specific
+		   output format */
+		return OpenWithAformat(graph_string, in_audio_format);
 
 	return std::make_unique<FfmpegFilter>(in_audio_format,
 					      out_audio_format,
 					      std::move(graph),
-					      std::move(buffer_src),
-					      std::move(buffer_sink));
+					      buffer_src,
+					      buffer_sink);
 }
 
 static std::unique_ptr<PreparedFilter>

src/filter/plugins/HdcdFilterPlugin.cxx

@@ -42,24 +42,13 @@ OpenHdcdFilter(AudioFormat &in_audio_format)
 {
 	Ffmpeg::FilterGraph graph;
 
-	auto buffer_src =
-		Ffmpeg::FilterContext::MakeAudioBufferSource(in_audio_format,
-							     *graph);
+	auto &buffer_src =
+		Ffmpeg::MakeAudioBufferSource(in_audio_format,
+					      *graph);
 
-	auto 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");
+	auto &buffer_sink = Ffmpeg::MakeAudioBufferSink(*graph);
 
+	graph.ParseSingleInOut(hdcd_graph, buffer_sink, buffer_src);
 	graph.CheckAndConfigure();
 
 	auto out_audio_format = in_audio_format;
@@ -69,8 +58,8 @@ OpenHdcdFilter(AudioFormat &in_audio_format)
 	return std::make_unique<FfmpegFilter>(in_audio_format,
 					      out_audio_format,
 					      std::move(graph),
-					      std::move(buffer_src),
-					      std::move(buffer_sink));
+					      buffer_src,
+					      buffer_sink);
 }
 
 class PreparedHdcdFilter final : public PreparedFilter {

src/lib/ffmpeg/ChannelLayout.hxx

+/*
+ * Copyright 2003-2021 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_FFMPEG_CHANNEL_LAYOUT_HXX
+#define MPD_FFMPEG_CHANNEL_LAYOUT_HXX
+
+extern "C" {
+#include <libavutil/channel_layout.h>
+}
+
+/**
+ * Convert a MPD channel count to a libavutil channel_layout bit mask.
+ */
+static constexpr uint64_t
+ToFfmpegChannelLayout(unsigned channels) noexcept
+{
+	switch (channels) {
+	case 1:
+		return AV_CH_LAYOUT_MONO;
+
+	case 2:
+		return AV_CH_LAYOUT_STEREO;
+
+	case 3:
+		return AV_CH_LAYOUT_SURROUND;
+
+	case 4:
+		// TODO is this AV_CH_LAYOUT_2_2?
+		return AV_CH_LAYOUT_QUAD;
+
+	case 5:
+		// TODO is this AV_CH_LAYOUT_5POINT0_BACK?
+		return AV_CH_LAYOUT_5POINT0;
+
+	case 6:
+		return AV_CH_LAYOUT_5POINT1;
+
+	case 7:
+		return AV_CH_LAYOUT_6POINT1;
+
+	case 8:
+		return AV_CH_LAYOUT_7POINT1;
+
+	default:
+		/* unreachable */
+		return 0;
+	}
+}
+
+#endif

src/lib/ffmpeg/DetectFilterFormat.cxx

@@ -62,8 +62,14 @@ DetectFilterOutputFormat(const AudioFormat &in_audio_format,
 	frame.Unref();
 
 	err = av_buffersink_get_frame(&buffer_sink, frame.get());
-	if (err < 0)
+	if (err < 0) {
+		if (err == AVERROR(EAGAIN))
+			/* one sample was not enough input data for
+			   the given filter graph */
+			return AudioFormat::Undefined();
+
 		throw MakeFfmpegError(err, "av_buffersink_get_frame() failed");
+	}
 
 	const SampleFormat sample_format = FromFfmpegSampleFormat(AVSampleFormat(frame->format));
 	if (sample_format == SampleFormat::UNDEFINED)

src/lib/ffmpeg/DetectFilterFormat.hxx

@@ -35,6 +35,9 @@ namespace Ffmpeg {
  * between.
  *
  * This function can throw if the FFmpeg filter fails.
+ *
+ * @return the output format or AudioFormat::Undefined() if it was not
+ * possible to determine the format
  */
 AudioFormat
 DetectFilterOutputFormat(const AudioFormat &in_audio_format,

src/lib/ffmpeg/Filter.cxx

@@ -18,10 +18,13 @@
  */
 
 #include "Filter.hxx"
+#include "ChannelLayout.hxx"
 #include "SampleFormat.hxx"
 #include "pcm/AudioFormat.hxx"
 #include "util/RuntimeError.hxx"
 
+#include <cinttypes>
+
 #include <stdio.h>
 
 namespace Ffmpeg {
@@ -36,9 +39,32 @@ RequireFilterByName(const char *name)
 	return *filter;
 }
 
-FilterContext
-FilterContext::MakeAudioBufferSource(AudioFormat &audio_format,
-				     AVFilterGraph &graph_ctx)
+static AVFilterContext &
+CreateFilter(const AVFilter &filt,
+	     const char *name, const char *args, void *opaque,
+	     AVFilterGraph &graph_ctx)
+{
+	AVFilterContext *context = nullptr;
+	int err = avfilter_graph_create_filter(&context, &filt,
+					       name, args, opaque,
+					       &graph_ctx);
+	if (err < 0)
+		throw MakeFfmpegError(err, "avfilter_graph_create_filter() failed");
+
+	return *context;
+}
+
+static AVFilterContext &
+CreateFilter(const AVFilter &filt,
+	     const char *name,
+	     AVFilterGraph &graph_ctx)
+{
+	return CreateFilter(filt, name, nullptr, nullptr, graph_ctx);
+}
+
+AVFilterContext &
+MakeAudioBufferSource(AudioFormat &audio_format,
+		      AVFilterGraph &graph_ctx)
 {
 	AVSampleFormat src_format = ToFfmpegSampleFormat(audio_format.format);
 	if (src_format == AV_SAMPLE_FMT_NONE) {
@@ -57,19 +83,72 @@ FilterContext::MakeAudioBufferSource(AudioFormat &audio_format,
 
 	char abuffer_args[256];
 	sprintf(abuffer_args,
-		"sample_rate=%u:sample_fmt=%s:channels=%u:time_base=1/%u",
+		"sample_rate=%u:sample_fmt=%s:channel_layout=0x%" PRIx64 ":time_base=1/%u",
 		audio_format.sample_rate,
 		av_get_sample_fmt_name(src_format),
-		audio_format.channels,
+		ToFfmpegChannelLayout(audio_format.channels),
 		audio_format.sample_rate);
 
-	return {RequireFilterByName("abuffer"), "abuffer", abuffer_args, nullptr, graph_ctx};
+	return CreateFilter(RequireFilterByName("abuffer"), "abuffer",
+			    abuffer_args, nullptr, graph_ctx);
+}
+
+AVFilterContext &
+MakeAudioBufferSink(AVFilterGraph &graph_ctx)
+{
+	return CreateFilter(RequireFilterByName("abuffersink"), "abuffersink",
+			    graph_ctx);
+}
+
+AVFilterContext &
+MakeAformat(AudioFormat &audio_format,
+	    AVFilterGraph &graph_ctx)
+{
+	AVSampleFormat dest_format = ToFfmpegSampleFormat(audio_format.format);
+	if (dest_format == AV_SAMPLE_FMT_NONE) {
+		switch (audio_format.format) {
+		case SampleFormat::S24_P32:
+			audio_format.format = SampleFormat::S32;
+			dest_format = AV_SAMPLE_FMT_S32;
+			break;
+
+		default:
+			audio_format.format = SampleFormat::S16;
+			dest_format = AV_SAMPLE_FMT_S16;
+			break;
+		}
+	}
+
+	char args[256];
+	sprintf(args,
+		"sample_rates=%u:sample_fmts=%s:channel_layouts=0x%" PRIx64,
+		audio_format.sample_rate,
+		av_get_sample_fmt_name(dest_format),
+		ToFfmpegChannelLayout(audio_format.channels));
+
+	return CreateFilter(RequireFilterByName("aformat"), "aformat",
+			    args, nullptr, graph_ctx);
+}
+
+AVFilterContext &
+MakeAutoAformat(AVFilterGraph &graph_ctx)
+{
+	return CreateFilter(RequireFilterByName("aformat"), "aformat",
+			    "sample_fmts=flt|s32|s16",
+			    nullptr, graph_ctx);
 }
 
-FilterContext
-FilterContext::MakeAudioBufferSink(AVFilterGraph &graph_ctx)
+void
+FilterGraph::ParseSingleInOut(const char *filters, AVFilterContext &in,
+			      AVFilterContext &out)
 {
-	return {RequireFilterByName("abuffersink"), "abuffersink", graph_ctx};
+	auto [inputs, outputs] = Parse(filters, {"out", in}, {"in", out});
+
+	if (inputs.get() != nullptr)
+		throw std::runtime_error("FFmpeg filter has an open input");
+
+	if (outputs.get() != nullptr)
+		throw std::runtime_error("FFmpeg filter has an open output");
 }
 
 } // namespace Ffmpeg

src/lib/ffmpeg/Filter.hxx

@@ -77,63 +77,38 @@ public:
 	}
 };
 
-class FilterContext {
-	AVFilterContext *context = nullptr;
-
-public:
-	FilterContext() = default;
-
-	FilterContext(const AVFilter &filt,
-		      const char *name, const char *args, void *opaque,
-		      AVFilterGraph &graph_ctx) {
-		int err = avfilter_graph_create_filter(&context, &filt,
-						       name, args, opaque,
-						       &graph_ctx);
-		if (err < 0)
-			throw MakeFfmpegError(err, "avfilter_graph_create_filter() failed");
-	}
-
-	FilterContext(const AVFilter &filt,
-		      const char *name,
-		      AVFilterGraph &graph_ctx)
-		:FilterContext(filt, name, nullptr, nullptr, graph_ctx) {}
-
-	FilterContext(FilterContext &&src) noexcept
-		:context(std::exchange(src.context, nullptr)) {}
-
-	~FilterContext() noexcept {
-		if (context != nullptr)
-			avfilter_free(context);
-	}
-
-	FilterContext &operator=(FilterContext &&src) noexcept {
-		using std::swap;
-		swap(context, src.context);
-		return *this;
-	}
-
-	/**
-	 * Create an "abuffer" filter.
-	 *
-	 * @param the input audio format; may be modified by the
-	 * function to ask the caller to do format conversion
-	 */
-	static FilterContext MakeAudioBufferSource(AudioFormat &audio_format,
-						   AVFilterGraph &graph_ctx);
+/**
+ * Create an "abuffer" filter.
+ *
+ * @param the input audio format; may be modified by the
+ * function to ask the caller to do format conversion
+ */
+AVFilterContext &
+MakeAudioBufferSource(AudioFormat &audio_format,
+		      AVFilterGraph &graph_ctx);
 
-	/**
-	 * Create an "abuffersink" filter.
-	 */
-	static FilterContext MakeAudioBufferSink(AVFilterGraph &graph_ctx);
+/**
+ * Create an "abuffersink" filter.
+ */
+AVFilterContext &
+MakeAudioBufferSink(AVFilterGraph &graph_ctx);
 
-	auto &operator*() noexcept {
-		return *context;
-	}
+/**
+ * Create an "aformat" filter.
+ *
+ * @param the output audio format; may be modified by the function if
+ * the given format is not supported by libavfilter
+ */
+AVFilterContext &
+MakeAformat(AudioFormat &audio_format,
+	    AVFilterGraph &graph_ctx);
 
-	auto *get() noexcept {
-		return context;
-	}
-};
+/**
+ * Create an "aformat" filter which automatically converts the output
+ * to a format supported by MPD.
+ */
+AVFilterContext &
+MakeAutoAformat(AVFilterGraph &graph_ctx);
 
 class FilterGraph {
 	AVFilterGraph *graph = nullptr;
@@ -180,6 +155,9 @@ public:
 		return std::make_pair(std::move(inputs), std::move(outputs));
 	}
 
+	void ParseSingleInOut(const char *filters, AVFilterContext &in,
+			      AVFilterContext &out);
+
 	std::pair<FilterInOut, FilterInOut> Parse(const char *filters) {
 		AVFilterInOut *inputs, *outputs;
 		int err = avfilter_graph_parse2(graph, filters,