From 75518e16a2c35400ac641975c74ff72b404cef69 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Sun, 18 Aug 2013 23:19:22 +0100
Subject: [PATCH] Try to make audio gain work again.

---
 src/lib/audio_buffers.cc | 13 +++++++++++++
 src/lib/audio_buffers.h  |  2 ++
 src/lib/player.cc        |  7 +++++++
 3 files changed, 22 insertions(+)

diff --git a/src/lib/audio_buffers.cc b/src/lib/audio_buffers.cc
index a15288a3b..e80142b8e 100644
--- a/src/lib/audio_buffers.cc
+++ b/src/lib/audio_buffers.cc
@@ -19,6 +19,7 @@
 
 #include <cassert>
 #include <cstring>
+#include <cmath>
 #include <stdexcept>
 #include "audio_buffers.h"
 
@@ -260,3 +261,15 @@ AudioBuffers::accumulate_frames (AudioBuffers const * from, int read_offset, int
 	}
 }
 
+/** @param dB gain in dB */
+void
+AudioBuffers::apply_gain (float dB)
+{
+	float const linear = pow (10, dB / 20);
+	
+	for (int i = 0; i < _channels; ++i) {
+		for (int j = 0; j < _frames; ++j) {
+			_data[i][j] *= linear;
+		}
+	}
+}
diff --git a/src/lib/audio_buffers.h b/src/lib/audio_buffers.h
index 0950f5d67..75bc686f8 100644
--- a/src/lib/audio_buffers.h
+++ b/src/lib/audio_buffers.h
@@ -57,6 +57,8 @@ public:
 	void make_silent (int c);
 	void make_silent (int from, int frames);
 
+	void apply_gain (float);
+
 	void copy_from (AudioBuffers const * from, int frames_to_copy, int read_offset, int write_offset);
 	void move (int from, int to, int frames);
 	void accumulate_channel (AudioBuffers const *, int, int);
diff --git a/src/lib/player.cc b/src/lib/player.cc
index f8ccb0142..ebc810214 100644
--- a/src/lib/player.cc
+++ b/src/lib/player.cc
@@ -300,6 +300,13 @@ Player::process_audio (weak_ptr<Piece> weak_piece, shared_ptr<const AudioBuffers
 	shared_ptr<AudioContent> content = dynamic_pointer_cast<AudioContent> (piece->content);
 	assert (content);
 
+	/* Gain */
+	if (content->audio_gain() != 0) {
+		shared_ptr<AudioBuffers> gain (new AudioBuffers (audio));
+		gain->apply_gain (content->audio_gain ());
+		audio = gain;
+	}
+
 	/* Resample */
 	if (content->content_audio_frame_rate() != content->output_audio_frame_rate()) {
 		shared_ptr<Resampler> r = resampler (content, true);
-- 
2.30.2