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sunny-overlay/media-sound/mixxx/files/mixxx-2.1.0-optimize-flac-decoding.patch

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From 497e9672dfd1079e28cadc9a413a0b8be00ed59d Mon Sep 17 00:00:00 2001
From: Uwe Klotz <uklotz@mixxx.org>
Date: Wed, 9 May 2018 12:08:59 +0200
Subject: [PATCH 1/4] Optimize FLAC decoding
---
src/sources/soundsourceflac.cpp | 51 ++++++++++++++++++++---------------------
src/sources/soundsourceflac.h | 2 --
2 files changed, 25 insertions(+), 28 deletions(-)
diff --git a/src/sources/soundsourceflac.cpp b/src/sources/soundsourceflac.cpp
index 3d68e05ce7..50cb0955e6 100644
--- a/src/sources/soundsourceflac.cpp
+++ b/src/sources/soundsourceflac.cpp
@@ -71,7 +71,6 @@ SoundSourceFLAC::SoundSourceFLAC(const QUrl& url)
m_decoder(nullptr),
m_maxBlocksize(0),
m_bitsPerSample(kBitsPerSampleDefault),
- m_sampleScaleFactor(CSAMPLE_ZERO),
m_curFrameIndex(0) {
}
@@ -345,25 +344,30 @@ FLAC__bool SoundSourceFLAC::flacEOF() {
return m_file.atEnd();
}
+namespace {
+
+// Workaround for improperly encoded FLAC files that may contain
+// garbage in the most significant, unused bits of decoded samples.
+// Required at least for libFLAC 1.3.2. This workaround might become
+// obsolete once libFLAC is taking care of these issues internally.
+// https://bugs.launchpad.net/mixxx/+bug/1769717
+// https://hydrogenaud.io/index.php/topic,61792.msg559045.html#msg559045
+//
+// We will shift decoded samples left by (32 - m_bitsPerSample) to
+// get rid of the garbage in the most significant bits before scaling.
+// The range of decoded integer sample values then becomes
+// [-2 ^ 31, 2 ^ 31 - 1]. Afterwards this integer range needs to be
+// scaled to [-CSAMPLE_PEAK, CSAMPLE_PEAK).
+
+const CSAMPLE kSampleScaleFactor = CSAMPLE_PEAK / (static_cast<FLAC__int32>(1) << 31);
+
inline
-FLAC__int32 adjustDecodedSample(FLAC__int32 decodedSample, SINT bitsPerSample) {
- // Workaround for improperly encoded FLAC files that may contain
- // garbage in the most significant, unused bits of decoded samples.
- // Required at least for libFLAC 1.3.2. This workaround might become
- // obsolete once libFLAC is taking care of these issues internally.
- // https://bugs.launchpad.net/mixxx/+bug/1769717
- // https://hydrogenaud.io/index.php/topic,61792.msg559045.html#msg559045
- FLAC__int32 signBit = static_cast<FLAC__int32>(1) << (bitsPerSample - 1);
- FLAC__int32 bitMask = (static_cast<FLAC__int32>(1) << bitsPerSample) - 1; // == (signBit << 1) - 1
- FLAC__int32 maskedSample = decodedSample & bitMask;
- if (maskedSample & signBit) {
- // Sign extension for negative values
- return maskedSample | ~bitMask;
- } else {
- return maskedSample;
- }
+CSAMPLE convertDecodedSample(FLAC__int32 decodedSample, int bitsPerSample) {
+ return (decodedSample << (32 - bitsPerSample)) * kSampleScaleFactor;
}
+} // anonymous namespace
+
FLAC__StreamDecoderWriteStatus SoundSourceFLAC::flacWrite(
const FLAC__Frame* frame, const FLAC__int32* const buffer[]) {
const SINT numChannels = frame->header.channels;
@@ -410,15 +414,15 @@ FLAC__StreamDecoderWriteStatus SoundSourceFLAC::flacWrite(
case 1: {
// optimized code for 1 channel (mono)
for (SINT i = 0; i < numWritableFrames; ++i) {
- *pSampleBuffer++ = adjustDecodedSample(buffer[0][i], m_bitsPerSample) * m_sampleScaleFactor;
+ *pSampleBuffer++ = convertDecodedSample(buffer[0][i], m_bitsPerSample);
}
break;
}
case 2: {
// optimized code for 2 channels (stereo)
for (SINT i = 0; i < numWritableFrames; ++i) {
- *pSampleBuffer++ = adjustDecodedSample(buffer[0][i], m_bitsPerSample) * m_sampleScaleFactor;
- *pSampleBuffer++ = adjustDecodedSample(buffer[1][i], m_bitsPerSample) * m_sampleScaleFactor;
+ *pSampleBuffer++ = convertDecodedSample(buffer[0][i], m_bitsPerSample);
+ *pSampleBuffer++ = convertDecodedSample(buffer[1][i], m_bitsPerSample);
}
break;
}
@@ -426,7 +430,7 @@ FLAC__StreamDecoderWriteStatus SoundSourceFLAC::flacWrite(
// generic code for multiple channels
for (SINT i = 0; i < numWritableFrames; ++i) {
for (SINT j = 0; j < channelCount(); ++j) {
- *pSampleBuffer++ = adjustDecodedSample(buffer[j][i], m_bitsPerSample) * m_sampleScaleFactor;
+ *pSampleBuffer++ = convertDecodedSample(buffer[j][i], m_bitsPerSample);
}
}
}
@@ -456,11 +460,6 @@ void SoundSourceFLAC::flacMetadata(const FLAC__StreamMetadata* metadata) {
// not set before
if ((bitsPerSample >= 4) && (bitsPerSample <= 32)) {
m_bitsPerSample = bitsPerSample;
- // Range of signed) sample values: [-2 ^ (bitsPerSample - 1), 2 ^ (bitsPerSample - 1) - 1]
- const uint32_t absSamplePeak = 1u << (bitsPerSample - 1);
- DEBUG_ASSERT(absSamplePeak > 0);
- // Scaled range of samples values: [-CSAMPLE_PEAK, CSAMPLE_PEAK)
- m_sampleScaleFactor = CSAMPLE_PEAK / absSamplePeak;
} else {
kLogger.warning()
<< "Invalid bits per sample:"
diff --git a/src/sources/soundsourceflac.h b/src/sources/soundsourceflac.h
index 05c74f7b5e..f4b3c1cb3c 100644
--- a/src/sources/soundsourceflac.h
+++ b/src/sources/soundsourceflac.h
@@ -49,8 +49,6 @@ class SoundSourceFLAC: public SoundSource {
SINT m_maxBlocksize; // in time samples (audio samples = time samples * chanCount)
SINT m_bitsPerSample;
- CSAMPLE m_sampleScaleFactor;
-
ReadAheadSampleBuffer m_sampleBuffer;
void invalidateCurFrameIndex() {
From 24c206f60278b8e9576ae661643162512ff1d19b Mon Sep 17 00:00:00 2001
From: Uwe Klotz <uklotz@mixxx.org>
Date: Wed, 9 May 2018 12:14:31 +0200
Subject: [PATCH 2/4] Add an assertion (just in case)
---
src/sources/soundsourceflac.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/sources/soundsourceflac.cpp b/src/sources/soundsourceflac.cpp
index 50cb0955e6..c01ab8455d 100644
--- a/src/sources/soundsourceflac.cpp
+++ b/src/sources/soundsourceflac.cpp
@@ -363,6 +363,7 @@ const CSAMPLE kSampleScaleFactor = CSAMPLE_PEAK / (static_cast<FLAC__int32>(1) <
inline
CSAMPLE convertDecodedSample(FLAC__int32 decodedSample, int bitsPerSample) {
+ DEBUG_ASSERT(sizeof(FLAC__int32) == 32); // exactly 32-bits required!
return (decodedSample << (32 - bitsPerSample)) * kSampleScaleFactor;
}
From 6dc1d5f1a7e291c36d5828fdaecc82a62845b758 Mon Sep 17 00:00:00 2001
From: Uwe Klotz <uklotz@mixxx.org>
Date: Wed, 9 May 2018 12:25:00 +0200
Subject: [PATCH 3/4] Get rid of (most) implicit assumptions
---
src/sources/soundsourceflac.cpp | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/sources/soundsourceflac.cpp b/src/sources/soundsourceflac.cpp
index c01ab8455d..478bac870e 100644
--- a/src/sources/soundsourceflac.cpp
+++ b/src/sources/soundsourceflac.cpp
@@ -359,12 +359,12 @@ namespace {
// [-2 ^ 31, 2 ^ 31 - 1]. Afterwards this integer range needs to be
// scaled to [-CSAMPLE_PEAK, CSAMPLE_PEAK).
-const CSAMPLE kSampleScaleFactor = CSAMPLE_PEAK / (static_cast<FLAC__int32>(1) << 31);
+const CSAMPLE kSampleScaleFactor = CSAMPLE_PEAK / (static_cast<FLAC__int32>(1) << std::numeric_limits<FLAC__int32>::digits);
inline
CSAMPLE convertDecodedSample(FLAC__int32 decodedSample, int bitsPerSample) {
- DEBUG_ASSERT(sizeof(FLAC__int32) == 32); // exactly 32-bits required!
- return (decodedSample << (32 - bitsPerSample)) * kSampleScaleFactor;
+ DEBUG_ASSERT(std::numeric_limits<FLAC__int32>::is_signed);
+ return (decodedSample << ((std::numeric_limits<FLAC__int32>::digits + 1) - bitsPerSample)) * kSampleScaleFactor;
}
} // anonymous namespace
From a0430875f6c4ad89c0fb09300ed19a64c60bbfb4 Mon Sep 17 00:00:00 2001
From: Uwe Klotz <uklotz@mixxx.org>
Date: Wed, 9 May 2018 15:16:58 +0200
Subject: [PATCH 4/4] Use constexpr and reword comments
---
src/sources/soundsourceflac.cpp | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/src/sources/soundsourceflac.cpp b/src/sources/soundsourceflac.cpp
index 478bac870e..1a95ac168c 100644
--- a/src/sources/soundsourceflac.cpp
+++ b/src/sources/soundsourceflac.cpp
@@ -352,14 +352,12 @@ namespace {
// obsolete once libFLAC is taking care of these issues internally.
// https://bugs.launchpad.net/mixxx/+bug/1769717
// https://hydrogenaud.io/index.php/topic,61792.msg559045.html#msg559045
-//
-// We will shift decoded samples left by (32 - m_bitsPerSample) to
-// get rid of the garbage in the most significant bits before scaling.
-// The range of decoded integer sample values then becomes
-// [-2 ^ 31, 2 ^ 31 - 1]. Afterwards this integer range needs to be
-// scaled to [-CSAMPLE_PEAK, CSAMPLE_PEAK).
-const CSAMPLE kSampleScaleFactor = CSAMPLE_PEAK / (static_cast<FLAC__int32>(1) << std::numeric_limits<FLAC__int32>::digits);
+// We will shift decoded samples left by (32 - m_bitsPerSample) to
+// get rid of the garbage in the most significant bits before scaling
+// to the range [-CSAMPLE_PEAK, CSAMPLE_PEAK - epsilon] with
+// epsilon = 1 / 2 ^ bitsPerSample.
+constexpr CSAMPLE kSampleScaleFactor = CSAMPLE_PEAK / (static_cast<FLAC__int32>(1) << std::numeric_limits<FLAC__int32>::digits);
inline
CSAMPLE convertDecodedSample(FLAC__int32 decodedSample, int bitsPerSample) {
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