From 64c3bdea8cba454d4404baded584ea0f0611b3ee Mon Sep 17 00:00:00 2001 From: Marco Nelissen Date: Wed, 27 Oct 2010 09:06:01 -0700 Subject: Fix off-by-two and other bugs in the visualization code. b/3137511 Change-Id: Ic431701e93c025bc417c9742e9af6bb2350c7dd6 --- media/libeffects/visualizer/EffectVisualizer.cpp | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) (limited to 'media/libeffects/visualizer') diff --git a/media/libeffects/visualizer/EffectVisualizer.cpp b/media/libeffects/visualizer/EffectVisualizer.cpp index 5505f14..c957dba 100644 --- a/media/libeffects/visualizer/EffectVisualizer.cpp +++ b/media/libeffects/visualizer/EffectVisualizer.cpp @@ -243,19 +243,22 @@ extern "C" int Visualizer_process( // derive capture scaling factor from peak value in current buffer // this gives more interesting captures for display. int32_t shift = 32; - for (size_t i = 0; i < inBuffer->frameCount; i++) { + int len = inBuffer->frameCount * 2; + for (size_t i = 0; i < len; i++) { int32_t smp = inBuffer->s16[i]; - if (smp < 0) smp = -smp; + if (smp < 0) smp = -smp - 1; // take care to keep the max negative in range int32_t clz = __builtin_clz(smp); if (shift > clz) shift = clz; } - // never scale by less than 8 to avoid returning unaltered PCM signal. - // add one to combine the division by 2 needed after summing left and right channels below - if (20 > shift) { - shift = (31 - 8 + 1) - shift; - } else { - shift = (3 + 1); + // A maximum amplitude signal will have 17 leading zeros, which we want to + // translate to a shift of 8 (for converting 16 bit to 8 bit) + shift = 25 - shift; + // Never scale by less than 8 to avoid returning unaltered PCM signal. + if (shift < 3) { + shift = 3; } + // add one to combine the division by 2 needed after summing left and right channels below + shift++; uint32_t captIdx; uint32_t inIdx; @@ -264,7 +267,7 @@ extern "C" int Visualizer_process( inIdx < inBuffer->frameCount && captIdx < pContext->mCaptureSize; inIdx++, captIdx++) { int32_t smp = inBuffer->s16[2 * inIdx] + inBuffer->s16[2 * inIdx + 1]; - smp = (smp + (1 << (shift - 1))) >> shift; + smp = smp >> shift; buf[captIdx] = ((uint8_t)smp)^0x80; } pContext->mCaptureIdx = captIdx; -- cgit v1.1