filter/ffmpeg: move code to ReadOutput()

src/filter/plugins/FfmpegFilter.cxx

@@ -34,6 +34,21 @@ FfmpegFilter::FfmpegFilter(const AudioFormat &in_audio_format,
 #endif
 }
 
+inline std::span<const std::byte>
+FfmpegFilter::ReadOutput()
+{
+	frame.Unref();
+
+	if (int err = av_buffersink_get_frame(&buffer_sink, frame.get()); err < 0) {
+		if (err == AVERROR(EAGAIN) || err == AVERROR_EOF)
+			return {};
+
+		throw MakeFfmpegError(err, "av_buffersink_get_frame() failed");
+	}
+
+	return Ffmpeg::InterleaveFrame(*frame, interleave_buffer);
+}
+
 std::span<const std::byte>
 FfmpegFilter::FilterPCM(std::span<const std::byte> src)
 {
@@ -58,17 +73,8 @@ FfmpegFilter::FilterPCM(std::span<const std::byte> src)
 
 	/* collect filtered data from the FFmpeg audio buffer sink */
 
-	frame.Unref();
-
-	if (int err = av_buffersink_get_frame(&buffer_sink, frame.get()); err < 0) {
-		if (err == AVERROR(EAGAIN) || err == AVERROR_EOF)
-			return {};
-
-		throw MakeFfmpegError(err, "av_buffersink_get_frame() failed");
-	}
-
 	/* TODO: call av_buffersink_get_frame() repeatedly?  Not
 	   possible with MPD's current Filter API */
 
-	return Ffmpeg::InterleaveFrame(*frame, interleave_buffer);
+	return ReadOutput();
 }

src/filter/plugins/FfmpegFilter.hxx

@@ -46,6 +46,9 @@ public:
 
 	/* virtual methods from class Filter */
 	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override;
+
+private:
+	std::span<const std::byte> ReadOutput();
 };
 
 #endif