decoder/flac: add options "probesize" and "analyzeduration"

https://bugs.musicpd.org/view.php?id=3876

NEWS

@@ -1,4 +1,6 @@
 ver 0.20.2 (not yet released)
+* decoder
+  - flac: add options "probesize" and "analyzeduration"
 
 ver 0.20.1 (2017/01/09)
 * input

doc/user.xml

@@ -2206,6 +2206,48 @@ run</programlisting>
           Decodes various codecs using
           <application>FFmpeg</application>.
         </para>
+
+        <informaltable>
+          <tgroup cols="2">
+            <thead>
+              <row>
+                <entry>Setting</entry>
+                <entry>Description</entry>
+              </row>
+            </thead>
+            <tbody>
+              <row>
+                <entry>
+                  <varname>analyzeduration</varname>
+                  <parameter>VALUE</parameter>
+                </entry>
+                <entry>
+                  Sets the FFmpeg muxer option
+                  <varname>analyzeduration</varname>, which specifies
+                  how many microseconds are analyzed to probe the
+                  input.  The <ulink
+                  url="https://ffmpeg.org/ffmpeg-formats.html">FFmpeg
+                  formats documentation</ulink> has more information.
+                </entry>
+              </row>
+
+              <row>
+                <entry>
+                  <varname>probesize</varname>
+                  <parameter>VALUE</parameter>
+                </entry>
+                <entry>
+                  Sets the FFmpeg muxer option
+                  <varname>probesize</varname>, which specifies
+                  probing size in bytes, i.e. the size of the data to
+                  analyze to get stream information.  The <ulink
+                  url="https://ffmpeg.org/ffmpeg-formats.html">FFmpeg
+                  formats documentation</ulink> has more information.
+                </entry>
+              </row>
+            </tbody>
+          </tgroup>
+        </informaltable>
       </section>
 
       <section id="flac_decoder">

src/decoder/plugins/FfmpegDecoderPlugin.cxx

@@ -56,6 +56,11 @@ extern "C" {
 #include <assert.h>
 #include <string.h>
 
+/**
+ * Muxer options to be passed to avformat_open_input().
+ */
+static AVDictionary *avformat_options = nullptr;
+
 static AVFormatContext *
 FfmpegOpenInput(AVIOContext *pb,
 		const char *filename,
@@ -67,7 +72,11 @@ FfmpegOpenInput(AVIOContext *pb,
 
 	context->pb = pb;
 
-	int err = avformat_open_input(&context, filename, fmt, nullptr);
+	AVDictionary *options = nullptr;
+	AtScopeExit(&options) { av_dict_free(&options); };
+	av_dict_copy(&options, avformat_options, 0);
+
+	int err = avformat_open_input(&context, filename, fmt, &options);
 	if (err < 0)
 		throw MakeFfmpegError(err, "avformat_open_input() failed");
 
@@ -75,12 +84,30 @@ FfmpegOpenInput(AVIOContext *pb,
 }
 
 static bool
-ffmpeg_init(gcc_unused const ConfigBlock &block)
+ffmpeg_init(const ConfigBlock &block)
 {
 	FfmpegInit();
+
+	static constexpr const char *option_names[] = {
+		"probesize",
+		"analyzeduration",
+	};
+
+	for (const char *name : option_names) {
+		const char *value = block.GetBlockValue(name);
+		if (value != nullptr)
+			av_dict_set(&avformat_options, name, value, 0);
+	}
+
 	return true;
 }
 
+static void
+ffmpeg_finish()
+{
+	av_dict_free(&avformat_options);
+}
+
 #if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 25, 0) /* FFmpeg 3.1 */
 
 gcc_pure
@@ -967,7 +994,7 @@ static const char *const ffmpeg_mime_types[] = {
 const struct DecoderPlugin ffmpeg_decoder_plugin = {
 	"ffmpeg",
 	ffmpeg_init,
-	nullptr,
+	ffmpeg_finish,
 	ffmpeg_decode,
 	nullptr,
 	nullptr,