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authorRyan Billing <ryjobil@gmail.com>2013-10-04 01:57:00 +1300
committerMichael Giacomelli <giac2000@hotmail.com>2013-12-15 22:24:08 +0100
commitd0918b98fa0cfba21208a4fb5ed153687b8f02c3 (patch)
tree006ef2bb902dfd83101fbfa3fe63b07f47d9e8e6 /apps/menus
parent5b5f0755d6d7fd9e3fdfdb479caeb7fafd0a9960 (diff)
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DSP Compressor: Sidechain, Exponential Atk/Rls
This is an improvement to the current compressor which I have added to my own Sansa Fuze V2 build. I am submitting here in case others find it interesting. Features added to the existing compressor: Attack, Look-ahead, Sidechain Filtering. Exponential attack and release characteristic response. Benefits from adding missing features: Attack: Preserve perceived "brightness" of tone by letting onset transients come through at a higher level than the rest of the compressed program material. Look-ahead: With Attack comes clipping on the leading several cycles of a transient onset. With look-ahead function, this can be pre-emptively mitigated with a slower gain change (less distortion). Look-ahead limiting is implemented to prevent clipping while keeping gain change ramp to an interval near 3ms instead of instant attack. The existing compressor implementation distorts the leading edge of a transient by causing instant gain change, resulting in log() distortion. This sounds "woofy" to me. Exponential Attack/Release: eMore natural sounding. On attack, this is a true straight line of 10dB per attack interval. Release is a little different, however, sounds natural as an analog compressor. Sidechain Filtering: Mild high-pass filter reduces response to low frequency onsets. For example, a hard kick drum is less likely to make the whole of the program material appear to fade in and out. Combined with a moderate attack time, such a transient will ride through with minimal audible artifact. Overall these changes make dynamic music sound more "open", more natural. The goal of a compressor is to make dyanamic music sound louder without necessarily sounding as though it has been compressed. I believe these changes come closer to this goal. Enjoy. If not, I am enjoying it Change-Id: I664eace546c364b815b4dc9ed4a72849231a0eb2 Reviewed-on: http://gerrit.rockbox.org/626 Tested: Purling Nayuki <cyq.yzfl@gmail.com> Reviewed-by: Michael Giacomelli <giac2000@hotmail.com>
Diffstat (limited to 'apps/menus')
-rw-r--r--apps/menus/sound_menu.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/apps/menus/sound_menu.c b/apps/menus/sound_menu.c
index fd192cb661..28cc257193 100644
--- a/apps/menus/sound_menu.c
+++ b/apps/menus/sound_menu.c
@@ -140,12 +140,15 @@ static int timestretch_callback(int action,const struct menu_item_ex *this_item)
MENUITEM_SETTING(compressor_knee,
&global_settings.compressor_settings.knee,
lowlatency_callback);
+ MENUITEM_SETTING(compressor_attack,
+ &global_settings.compressor_settings.attack_time,
+ lowlatency_callback);
MENUITEM_SETTING(compressor_release,
&global_settings.compressor_settings.release_time,
lowlatency_callback);
MAKE_MENU(compressor_menu,ID2P(LANG_COMPRESSOR), NULL, Icon_NOICON,
&compressor_threshold, &compressor_gain, &compressor_ratio,
- &compressor_knee, &compressor_release);
+ &compressor_knee, &compressor_attack, &compressor_release);
#endif
#if (CONFIG_CODEC == MAS3587F) || (CONFIG_CODEC == MAS3539F)