Provide high resolution volume and prescaler to hosted targets.

HAVE_SW_VOLUME_CONTROL is required and at this time only affects the
SDL targets using pcm-sdl.c.

Enables balance control in SDL targets, unless mono volume is in use.

Compiles software volume control as unbuffered when
PCM_SW_VOLUME_UNBUFFERED is defined. This avoids the overhead and
extra latency introduced by the double buffer when it is not needed.
Use this config when the target's PCM driver is buffered and sufficient
latency exists to perform safely the volume scaling.

Simulated targets that are double-buffered when made as native targets
remain so in the sim in order to run the same code.

Change-Id: Ifa77d2d3ae7376c65afecdfc785a084478cb5ffb
Reviewed-on: http://gerrit.rockbox.org/457
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested-by: Michael Sevakis <jethead71@rockbox.org>

5 files changed, 60 insertions, 13 deletions

diff --git a/firmware/export/audiohw.h b/firmware/export/audiohw.h
index 843ac0c0c4..4379c20a79 100644
--- a/firmware/export/audiohw.h
+++ b/firmware/export/audiohw.h
@@ -111,11 +111,6 @@ struct sound_settings_info
 #include "hosted_codec.h"
 #endif
 
-#if defined(SIMULATOR) && !defined(HAVE_SW_VOLUME_CONTROL)
-/* For now, without software volume control, sim only supports mono control */
-#define AUDIOHW_HAVE_MONO_VOLUME
-#endif
-
 /* convert caps into defines */
 #ifdef AUDIOHW_CAPS
 /* Tone controls */
diff --git a/firmware/export/config.h b/firmware/export/config.h
index 6a4a4648c8..7d7a18cc23 100644
--- a/firmware/export/config.h
+++ b/firmware/export/config.h
@@ -1139,6 +1139,24 @@ Lyre prototype 1 */
 #define ROCKBOX_HAS_LOGDISKF
 #endif
 
+#if defined(HAVE_SDL_AUDIO) \
+    && !(CONFIG_PLATFORM & PLATFORM_MAEMO5) \
+    && !defined(HAVE_SW_VOLUME_CONTROL) \
+    && CONFIG_CODEC == SWCODEC
+/* SW volume is needed for accurate control and no double buffering should be
+ * required. If target uses SW volume, then its definitions are used instead
+ * so things are as on target. */
+#define HAVE_SW_VOLUME_CONTROL
+#define PCM_SW_VOLUME_UNBUFFERED /* pcm driver itself is buffered */
+#ifdef SIMULATOR
+/* For sim, nice res for ~ -127dB..+36dB that so far covers all targets */
+#define PCM_SW_VOLUME_FRACBITS  (24)
+#else
+/* For app, use fractional-only setup for -79..+0, no large-integer math */
+#define PCM_SW_VOLUME_FRACBITS  (16)
+#endif /* SIMULATOR */
+#endif /* default SDL SW volume conditions */
+
 /* null audiohw setting macro for when codec header is included for reasons
    other than audio support */
 #define AUDIOHW_SETTING(name, us, nd, st, minv, maxv, defv, expr...)
diff --git a/firmware/export/hosted_codec.h b/firmware/export/hosted_codec.h
index 72495709e8..f5e92ed297 100644
--- a/firmware/export/hosted_codec.h
+++ b/firmware/export/hosted_codec.h
@@ -21,8 +21,13 @@
 #ifndef HOSTED_CODEC_H
 #define HOSTED_CODEC_H
 
+#if defined(HAVE_SDL_AUDIO) \
+    && !(CONFIG_PLATFORM & PLATFORM_MAEMO5)
+AUDIOHW_SETTING(VOLUME,      "dB",   0,  1, -80,   0,   0)
+#else
 #define AUDIOHW_CAPS    (MONO_VOL_CAP)
 AUDIOHW_SETTING(VOLUME,      "dB",   0,  1, -99,   0,   0)
+#endif /* CONFIG_PLATFORM & PLATFORM_SDL */
 
 #if (CONFIG_PLATFORM & PLATFORM_ANDROID)
 /* Bass and treble tone controls */
diff --git a/firmware/export/pcm-internal.h b/firmware/export/pcm-internal.h
index 03e5c5e6e7..2b73f64ef6 100644
--- a/firmware/export/pcm-internal.h
+++ b/firmware/export/pcm-internal.h
@@ -27,13 +27,36 @@
 #ifdef HAVE_SW_VOLUME_CONTROL
 /* Default settings - architecture may have other optimal values */
 
-#define PCM_FACTOR_BITS    15 /* Allows -73 to +6dB gain, sans 64-bit math */
+#ifndef PCM_SW_VOLUME_FRACBITS
+/* Allows -73 to +6dB gain, sans large integer math */
+#define PCM_SW_VOLUME_FRACBITS  (15)
+#endif
+
+/* Constants selected based on integer math overflow avoidance */
+#if PCM_SW_VOLUME_FRACBITS <= 16
+#define PCM_FACTOR_MAX      0x00010000u
+#define PCM_FACTOR_UNITY    (1u << PCM_SW_VOLUME_FRACBITS)
+#elif PCM_SW_VOLUME_FRACBITS <= 31
+#define PCM_FACTOR_MAX      0x80000000u
+#define PCM_FACTOR_UNITY    (1u << PCM_SW_VOLUME_FRACBITS)
+#endif /* PCM_SW_VOLUME_FRACBITS */
+
+#ifdef PCM_SW_VOLUME_UNBUFFERED
+/* Copies buffer with volume scaling applied */
+void pcm_sw_volume_copy_buffer(void *dst, const void *src, size_t size);
+#define pcm_copy_buffer pcm_sw_volume_copy_buffer
+#else /* !PCM_SW_VOLUME_UNBUFFERED */
+#ifdef HAVE_SDL_AUDIO
+#define pcm_copy_buffer memcpy
+#endif
+#ifndef PCM_PLAY_DBL_BUF_SAMPLES
 #define PCM_PLAY_DBL_BUF_SAMPLES 1024 /* Max 4KByte chunks */
+#endif
+#ifndef PCM_DBL_BUF_BSS
 #define PCM_DBL_BUF_BSS               /* In DRAM, uncached may be better */
-#define PCM_FACTOR_MIN        0x00000 /* Minimum final factor */
-#define PCM_FACTOR_MAX        0x10000 /* Maximum final factor */
+#endif
+#endif /* PCM_SW_VOLUME_UNBUFFERED */
 
-#define PCM_FACTOR_UNITY      (1 << PCM_FACTOR_BITS)
 #endif /* HAVE_SW_VOLUME_CONTROL */
 
 #define PCM_SAMPLE_SIZE     (2 * sizeof (int16_t))
@@ -84,22 +107,22 @@ static FORCE_INLINE enum pcm_dma_status pcm_play_call_status_cb(
 static FORCE_INLINE enum pcm_dma_status
 pcm_play_dma_status_callback(enum pcm_dma_status status)
 {
-#ifdef HAVE_SW_VOLUME_CONTROL
+#if defined(HAVE_SW_VOLUME_CONTROL) && !defined(PCM_SW_VOLUME_UNBUFFERED)
     extern enum pcm_dma_status
         pcm_play_dma_status_callback_int(enum pcm_dma_status status);
     return pcm_play_dma_status_callback_int(status);
 #else
     return pcm_play_call_status_cb(status);
-#endif /* HAVE_SW_VOLUME_CONTROL */
+#endif /* HAVE_SW_VOLUME_CONTROL && !PCM_SW_VOLUME_UNBUFFERED */
 }
 
-#ifdef HAVE_SW_VOLUME_CONTROL
+#if defined(HAVE_SW_VOLUME_CONTROL) && !defined(PCM_SW_VOLUME_UNBUFFERED)
 void pcm_play_dma_start_int(const void *addr, size_t size);
 void pcm_play_dma_pause_int(bool pause);
 void pcm_play_dma_stop_int(void);
 void pcm_play_stop_int(void);
 const void *pcm_play_dma_get_peak_buffer_int(int *count);
-#endif /* HAVE_SW_VOLUME_CONTROL */
+#endif /* HAVE_SW_VOLUME_CONTROL && !PCM_SW_VOLUME_UNBUFFERED */
 
 /* Called by the bottom layer ISR when more data is needed. Returns true
  * if a new buffer is available, false otherwise. */
diff --git a/firmware/export/pcm_sw_volume.h b/firmware/export/pcm_sw_volume.h
index b5d70654a1..5088eadeb1 100644
--- a/firmware/export/pcm_sw_volume.h
+++ b/firmware/export/pcm_sw_volume.h
@@ -21,6 +21,12 @@
 #ifndef PCM_SW_VOLUME_H
 #define PCM_SW_VOLUME_H
 
+/***
+ ** Note: Only PCM drivers that are themselves buffered should use the
+ ** PCM_SW_VOLUME_UNBUFFERED configuration. This may be part of the platform,
+ ** the library or a hardware necessity. Normally, it shouldn't be used and
+ ** only the port developer can properly decide.
+ **/
 #ifdef HAVE_SW_VOLUME_CONTROL
 
 #include <audiohw.h>