Enable setting of global output samplerate on certain targets.

Replaces the NATIVE_FREQUENCY constant with a configurable frequency.

The user may select 48000Hz if the hardware supports it. The default is
still 44100Hz and the minimum is 44100Hz. The setting is located in the
playback settings, under "Frequency".

"Frequency" was duplicated in english.lang for now to avoid having to
fix every .lang file for the moment and throwing everything out of sync
because of the new play_frequency feature in features.txt. The next
cleanup should combine it with the one included for recording and
generalize the ID label.

If the hardware doesn't support 48000Hz, no setting will be available.

On particular hardware where very high rates are practical and desireable,
the upper bound can be extended by patching.

The PCM mixer can be configured to play at the full hardware frequency
range. The DSP core can configure to the hardware minimum up to the
maximum playback setting (some buffers must be reserved according to
the maximum rate).

If only 44100Hz is supported or possible on a given target for playback,
using the DSP and mixer at other samperates is possible if the hardware
offers them.

Change-Id: I6023cf0c0baa8bc6292b6919b4dd3618a6a25622
Reviewed-on: http://gerrit.rockbox.org/479
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested-by: Michael Sevakis <jethead71@rockbox.org>

3 files changed, 8 insertions, 1 deletions

diff --git a/apps/plugins/mpegplayer/audio_thread.c b/apps/plugins/mpegplayer/audio_thread.c
index 1c167ea2a2..764ad111f2 100644
--- a/apps/plugins/mpegplayer/audio_thread.c
+++ b/apps/plugins/mpegplayer/audio_thread.c
@@ -481,6 +481,7 @@ static void audio_thread(void)
     init_mad();
 
     td.dsp = rb->dsp_get_config(CODEC_IDX_AUDIO);
+    rb->dsp_configure(td.dsp, DSP_SET_OUT_FREQUENCY, CLOCK_RATE);
 #ifdef HAVE_PITCHCONTROL
     rb->sound_set_pitch(PITCH_SPEED_100);
     rb->dsp_set_timestretch(PITCH_SPEED_100);
diff --git a/apps/plugins/mpegplayer/mpegplayer.h b/apps/plugins/mpegplayer/mpegplayer.h
index 32cc7b25be..4ddf0ca7b1 100644
--- a/apps/plugins/mpegplayer/mpegplayer.h
+++ b/apps/plugins/mpegplayer/mpegplayer.h
@@ -44,7 +44,7 @@
 #define AUDIOBUF_ALLOC_SIZE (AUDIOBUF_SIZE+AUDIOBUF_GUARD_SIZE)
 
 /** PCM buffer **/
-#define CLOCK_RATE NATIVE_FREQUENCY /* Our clock rate in ticks/second (samplerate) */
+#define CLOCK_RATE 44100 /* Our clock rate in ticks/second (samplerate) */
 
 /* Define this as "1" to have a test tone instead of silence clip */
 #define SILENCE_TEST_TONE 0
diff --git a/apps/plugins/mpegplayer/pcm_output.c b/apps/plugins/mpegplayer/pcm_output.c
index 3af8e91adc..82e3584277 100644
--- a/apps/plugins/mpegplayer/pcm_output.c
+++ b/apps/plugins/mpegplayer/pcm_output.c
@@ -51,6 +51,8 @@ static uint32_t volatile clock_time IBSS_ATTR; /* Timestamp adjusted */
 static int pcm_skipped = 0;
 static int pcm_underruns = 0;
 
+static unsigned int old_sampr = 0;
+
 /* Small silence clip. ~5.80ms @ 44.1kHz */
 static int16_t silence[256*2] ALIGNED_ATTR(4) = { 0 };
 
@@ -380,9 +382,13 @@ bool pcm_output_init(void)
     }
 #endif
 
+    old_sampr = rb->mixer_get_frequency();
+    rb->mixer_set_frequency(CLOCK_RATE);
     return true;
 }
 
 void pcm_output_exit(void)
 {
+    if (old_sampr != 0)
+        rb->mixer_set_frequency(old_sampr);
 }