Commit FS#12150 - Fully-functional audio mixer - and finally whip old limitations about playback of voice and other sounds when paused. Channels are independent in state and amplitude. Fade on stop/pause is handled by the channel's volume control rather than global volume which means it now works from anywhere. Opens up the possibility of plugin sounds during music playback by merely adding an additional channel enum. If any PCM drivers were not properly modified, see one of the last comments in the task for a description of the simple change that is expected. Some params are tunable in firmware/export/pcm-mixer.h as well.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30097 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 118 insertions, 0 deletions

diff --git a/firmware/target/arm/pcm-mixer-armv6.c b/firmware/target/arm/pcm-mixer-armv6.c
new file mode 100644
index 0000000000..94eecd0f90
--- /dev/null
+++ b/firmware/target/arm/pcm-mixer-armv6.c
@@ -0,0 +1,118 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2011 by Michael Sevakis
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#define MIXER_OPTIMIZED_MIX_SAMPLES
+#define MIXER_OPTIMIZED_WRITE_SAMPLES
+
+/* Mix channels' samples and apply gain factors */
+static FORCE_INLINE void mix_samples(void *out,
+                                     void *src0,
+                                     int32_t src0_amp,
+                                     void *src1,
+                                     int32_t src1_amp,
+                                     size_t size)
+{
+    uint32_t s0, s1;
+
+    if (src0_amp == MIX_AMP_UNITY && src1_amp == MIX_AMP_UNITY)
+    {
+        /* Both are unity amplitude */
+        asm volatile (
+        "1:                      \n"
+            "ldr    %4, [%1], #4 \n"
+            "ldr    %5, [%2], #4 \n"
+            "subs   %3, %3, #4   \n"
+            "qadd16 %5, %5, %4   \n"
+            "str    %5, [%0], #4 \n"
+            "bhi    1b           \n"
+            : "+r"(out), "+r"(src0), "+r"(src1), "+r"(size),
+              "=&r"(s0), "=&r"(s1));
+    }
+    else
+    {
+        /* One or neither are unity amplitude */
+        uint32_t tmp;
+        asm volatile (
+        "1:                             \n"
+            "ldr    %4, [%1], #4        \n"
+            "ldr    %5, [%2], #4        \n"
+            "subs   %3, %3, #4          \n"
+            "smulwb %6, %7, %4          \n"
+            "smulwt %4, %7, %4          \n"
+            "smlawb %6, %8, %5, %6      \n"
+            "smlawt %4, %8, %5, %4      \n"
+            "ssat   %6, #16, %6         \n"
+            "ssat   %4, #16, %4         \n"
+            "pkhbt  %6, %6, %4, asl #16 \n"
+            "str    %6, [%0], #4        \n"
+            "bhi    1b                  \n"
+            : "+r"(out), "+r"(src0), "+r"(src1), "+r"(size),
+              "=&r"(s0), "=&r"(s1), "=&r"(tmp)
+            : "r"(src0_amp), "r"(src1_amp));
+    }
+}
+
+/* Write channel's samples and apply gain factor */
+static FORCE_INLINE void write_samples(void *out,
+                                       void *src,
+                                       int32_t amp,
+                                       size_t size)
+{
+    if (LIKELY(amp == MIX_AMP_UNITY))
+    {
+        /* Channel is unity amplitude */
+        asm volatile (
+            "ands       r1, %2, #0x1f  \n"
+            "beq        2f             \n"
+        "1:                            \n"
+            "ldr        r0, [%1], #4   \n"
+            "subs       r1, r1, #4     \n"
+            "str        r0, [%0], #4   \n"
+            "bne        1b             \n"
+            "bics       %2, %2, #0x1f  \n"
+            "beq        3f             \n"
+        "2:                            \n"
+            "ldmia      %1!, { r0-r7 } \n"
+            "subs       %2, %2, #32    \n"
+            "stmia      %0!, { r0-r7 } \n"
+            "bhi        2b             \n"
+        "3:                            \n"
+            : "+r"(out), "+r"(src), "+r"(size)
+            :
+            : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7");
+    }
+    else
+    {
+        /* Channel needs amplitude cut */
+        uint32_t s, tmp;
+        asm volatile(
+        "1:                             \n"
+            "ldr    %3, [%1], #4        \n"
+            "subs   %2, %2, #4          \n"
+            "smulwt %4, %5, %3          \n"
+            "smulwb %3, %5, %3          \n"
+            "pkhbt  %4, %3, %4, asl #16 \n"
+            "str    %4, [%0], #4        \n"
+            "bhi    1b                  \n"
+            : "+r"(out), "+r"(src), "+r"(size),
+              "=&r"(s), "=&r"(tmp)
+            : "r"(amp));
+    }     
+}