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/*
* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include <math.h>
#include <stdlib.h>
#include "deflickering.h"
#include "trace.h"
#include "signal_processing_library.h"
#include "sort.h"
namespace webrtc {
// Detection constants
enum { kFrequencyDeviation = 39 }; // (Q4) Maximum allowed deviation for detection
enum { kMinFrequencyToDetect = 32 }; // (Q4) Minimum frequency that can be detected
enum { kNumFlickerBeforeDetect = 2 }; // Number of flickers before we accept detection
enum { kMeanValueScaling = 4 }; // (Q4) In power of 2
enum { kZeroCrossingDeadzone = 10 }; // Deadzone region in terms of pixel values
// Deflickering constants
// Compute the quantiles over 1 / DownsamplingFactor of the image.
enum { kDownsamplingFactor = 8 };
enum { kLog2OfDownsamplingFactor = 3 };
// To generate in Matlab:
// >> probUW16 = round(2^11 * [0.05,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,0.95,0.97]);
// >> fprintf('%d, ', probUW16)
// Resolution reduced to avoid overflow when multiplying with the (potentially) large
// number of pixels.
const WebRtc_UWord16 VPMDeflickering::_probUW16[kNumProbs] =
{102, 205, 410, 614, 819, 1024, 1229, 1434, 1638, 1843, 1946, 1987}; // <Q11>
// To generate in Matlab:
// >> numQuants = 14; maxOnlyLength = 5;
// >> weightUW16 = round(2^15 * [linspace(0.5, 1.0, numQuants - maxOnlyLength)]);
// >> fprintf('%d, %d,\n ', weightUW16);
const WebRtc_UWord16 VPMDeflickering::_weightUW16[kNumQuants - kMaxOnlyLength] =
{16384, 18432, 20480, 22528, 24576, 26624, 28672, 30720, 32768}; // <Q15>
VPMDeflickering::VPMDeflickering() :
_id(0)
{
Reset();
}
VPMDeflickering::~VPMDeflickering()
{
}
WebRtc_Word32
VPMDeflickering::ChangeUniqueId(const WebRtc_Word32 id)
{
_id = id;
return 0;
}
void
VPMDeflickering::Reset()
{
_meanBufferLength = 0;
_detectionState = 0;
_frameRate = 0;
memset(_meanBuffer, 0, sizeof(WebRtc_Word32) * kMeanBufferLength);
memset(_timestampBuffer, 0, sizeof(WebRtc_Word32) * kMeanBufferLength);
// Initialize the history with a uniformly distributed histogram
_quantHistUW8[0][0] = 0;
_quantHistUW8[0][kNumQuants - 1] = 255;
for (WebRtc_Word32 i = 0; i < kNumProbs; i++)
{
_quantHistUW8[0][i + 1] = static_cast<WebRtc_UWord8>((WEBRTC_SPL_UMUL_16_16(
_probUW16[i], 255) + (1 << 10)) >> 11); // Unsigned round. <Q0>
}
for (WebRtc_Word32 i = 1; i < kFrameHistorySize; i++)
{
memcpy(_quantHistUW8[i], _quantHistUW8[0], sizeof(WebRtc_UWord8) * kNumQuants);
}
}
WebRtc_Word32
VPMDeflickering::ProcessFrame(WebRtc_UWord8* frame,
const WebRtc_UWord32 width,
const WebRtc_UWord32 height,
const WebRtc_UWord32 timestamp,
VideoProcessingModule::FrameStats& stats)
{
WebRtc_UWord32 frameMemory;
WebRtc_UWord8 quantUW8[kNumQuants];
WebRtc_UWord8 maxQuantUW8[kNumQuants];
WebRtc_UWord8 minQuantUW8[kNumQuants];
WebRtc_UWord16 targetQuantUW16[kNumQuants];
WebRtc_UWord16 incrementUW16;
WebRtc_UWord8 mapUW8[256];
WebRtc_UWord16 tmpUW16;
WebRtc_UWord32 tmpUW32;
if (frame == NULL)
{
WEBRTC_TRACE(webrtc::kTraceError, webrtc::kTraceVideoPreocessing, _id, "Null frame pointer");
return VPM_GENERAL_ERROR;
}
// Stricter height check due to subsampling size calculation below.
if (width == 0 || height < 2)
{
WEBRTC_TRACE(webrtc::kTraceError, webrtc::kTraceVideoPreocessing, _id, "Invalid frame size");
return VPM_GENERAL_ERROR;
}
if (!VideoProcessingModule::ValidFrameStats(stats))
{
WEBRTC_TRACE(webrtc::kTraceError, webrtc::kTraceVideoPreocessing, _id, "Invalid frame stats");
return VPM_GENERAL_ERROR;
}
if (PreDetection(timestamp, stats) == -1)
{
return VPM_GENERAL_ERROR;
}
// Flicker detection
WebRtc_Word32 detFlicker = DetectFlicker();
if (detFlicker < 0)
{ // Error
return VPM_GENERAL_ERROR;
}
else if (detFlicker != 1)
{
return 0;
}
// Size of luminance component
const WebRtc_UWord32 ySize = height * width;
const WebRtc_UWord32 ySubSize = width * (((height - 1) >>
kLog2OfDownsamplingFactor) + 1);
WebRtc_UWord8* ySorted = new WebRtc_UWord8[ySubSize];
WebRtc_UWord32 sortRowIdx = 0;
for (WebRtc_UWord32 i = 0; i < height; i += kDownsamplingFactor)
{
memcpy(ySorted + sortRowIdx * width, frame + i * width, width);
sortRowIdx++;
}
webrtc::Sort(ySorted, ySubSize, webrtc::TYPE_UWord8);
WebRtc_UWord32 probIdxUW32 = 0;
quantUW8[0] = 0;
quantUW8[kNumQuants - 1] = 255;
// Ensure we won't get an overflow below.
// In practice, the number of subsampled pixels will not become this large.
if (ySubSize > (1 << 21) - 1)
{
WEBRTC_TRACE(webrtc::kTraceError, webrtc::kTraceVideoPreocessing, _id,
"Subsampled number of pixels too large");
return -1;
}
for (WebRtc_Word32 i = 0; i < kNumProbs; i++)
{
probIdxUW32 = WEBRTC_SPL_UMUL_32_16(ySubSize, _probUW16[i]) >> 11; // <Q0>
quantUW8[i + 1] = ySorted[probIdxUW32];
}
delete [] ySorted;
ySorted = NULL;
// Shift history for new frame.
memmove(_quantHistUW8[1], _quantHistUW8[0], (kFrameHistorySize - 1) * kNumQuants *
sizeof(WebRtc_UWord8));
// Store current frame in history.
memcpy(_quantHistUW8[0], quantUW8, kNumQuants * sizeof(WebRtc_UWord8));
// We use a frame memory equal to the ceiling of half the frame rate to ensure we
// capture an entire period of flicker.
frameMemory = (_frameRate + (1 << 5)) >> 5; // Unsigned ceiling. <Q0>
// _frameRate in Q4.
if (frameMemory > kFrameHistorySize)
{
frameMemory = kFrameHistorySize;
}
// Get maximum and minimum.
for (WebRtc_Word32 i = 0; i < kNumQuants; i++)
{
maxQuantUW8[i] = 0;
minQuantUW8[i] = 255;
for (WebRtc_UWord32 j = 0; j < frameMemory; j++)
{
if (_quantHistUW8[j][i] > maxQuantUW8[i])
{
maxQuantUW8[i] = _quantHistUW8[j][i];
}
if (_quantHistUW8[j][i] < minQuantUW8[i])
{
minQuantUW8[i] = _quantHistUW8[j][i];
}
}
}
// Get target quantiles.
for (WebRtc_Word32 i = 0; i < kNumQuants - kMaxOnlyLength; i++)
{
targetQuantUW16[i] = static_cast<WebRtc_UWord16>((WEBRTC_SPL_UMUL_16_16(
_weightUW16[i], maxQuantUW8[i]) + WEBRTC_SPL_UMUL_16_16((1 << 15) -
_weightUW16[i], minQuantUW8[i])) >> 8); // <Q7>
}
for (WebRtc_Word32 i = kNumQuants - kMaxOnlyLength; i < kNumQuants; i++)
{
targetQuantUW16[i] = ((WebRtc_UWord16)maxQuantUW8[i]) << 7;
}
// Compute the map from input to output pixels.
WebRtc_UWord16 mapUW16; // <Q7>
for (WebRtc_Word32 i = 1; i < kNumQuants; i++)
{
// As quant and targetQuant are limited to UWord8, we're safe to use Q7 here.
tmpUW32 = static_cast<WebRtc_UWord32>(targetQuantUW16[i] -
targetQuantUW16[i - 1]); // <Q7>
tmpUW16 = static_cast<WebRtc_UWord16>(quantUW8[i] - quantUW8[i - 1]); // <Q0>
if (tmpUW16 > 0)
{
incrementUW16 = static_cast<WebRtc_UWord16>(WebRtcSpl_DivU32U16(tmpUW32,
tmpUW16)); // <Q7>
}
else
{
// The value is irrelevant; the loop below will only iterate once.
incrementUW16 = 0;
}
mapUW16 = targetQuantUW16[i - 1];
for (WebRtc_UWord32 j = quantUW8[i - 1]; j < (WebRtc_UWord32)(quantUW8[i] + 1); j++)
{
mapUW8[j] = (WebRtc_UWord8)((mapUW16 + (1 << 6)) >> 7); // Unsigned round. <Q0>
mapUW16 += incrementUW16;
}
}
// Map to the output frame.
for (WebRtc_UWord32 i = 0; i < ySize; i++)
{
frame[i] = mapUW8[frame[i]];
}
// Frame was altered, so reset stats.
VideoProcessingModule::ClearFrameStats(stats);
return 0;
}
/**
Performs some pre-detection operations. Must be called before
DetectFlicker().
\param[in] timestamp Timestamp of the current frame.
\param[in] stats Statistics of the current frame.
\return 0: Success\n
2: Detection not possible due to flickering frequency too close to
zero.\n
-1: Error
*/
WebRtc_Word32
VPMDeflickering::PreDetection(const WebRtc_UWord32 timestamp,
const VideoProcessingModule::FrameStats& stats)
{
WebRtc_Word32 meanVal; // Mean value of frame (Q4)
WebRtc_UWord32 frameRate = 0;
WebRtc_Word32 meanBufferLength; // Temp variable
meanVal = ((stats.sum << kMeanValueScaling) / stats.numPixels);
/* Update mean value buffer.
* This should be done even though we might end up in an unreliable detection.
*/
memmove(_meanBuffer + 1, _meanBuffer, (kMeanBufferLength - 1) * sizeof(WebRtc_Word32));
_meanBuffer[0] = meanVal;
/* Update timestamp buffer.
* This should be done even though we might end up in an unreliable detection.
*/
memmove(_timestampBuffer + 1, _timestampBuffer, (kMeanBufferLength - 1) *
sizeof(WebRtc_UWord32));
_timestampBuffer[0] = timestamp;
/* Compute current frame rate (Q4) */
if (_timestampBuffer[kMeanBufferLength - 1] != 0)
{
frameRate = ((90000 << 4) * (kMeanBufferLength - 1));
frameRate /= (_timestampBuffer[0] - _timestampBuffer[kMeanBufferLength - 1]);
}else if (_timestampBuffer[1] != 0)
{
frameRate = (90000 << 4) / (_timestampBuffer[0] - _timestampBuffer[1]);
}
/* Determine required size of mean value buffer (_meanBufferLength) */
if (frameRate == 0) {
meanBufferLength = 1;
}
else {
meanBufferLength = (kNumFlickerBeforeDetect * frameRate) / kMinFrequencyToDetect;
}
/* Sanity check of buffer length */
if (meanBufferLength >= kMeanBufferLength)
{
/* Too long buffer. The flickering frequency is too close to zero, which
* makes the estimation unreliable.
*/
_meanBufferLength = 0;
return 2;
}
_meanBufferLength = meanBufferLength;
if ((_timestampBuffer[_meanBufferLength - 1] != 0) && (_meanBufferLength != 1))
{
frameRate = ((90000 << 4) * (_meanBufferLength - 1));
frameRate /= (_timestampBuffer[0] - _timestampBuffer[_meanBufferLength - 1]);
}else if (_timestampBuffer[1] != 0)
{
frameRate = (90000 << 4) / (_timestampBuffer[0] - _timestampBuffer[1]);
}
_frameRate = frameRate;
return 0;
}
/**
This function detects flicker in the video stream. As a side effect the mean value
buffer is updated with the new mean value.
\return 0: No flickering detected\n
1: Flickering detected\n
2: Detection not possible due to unreliable frequency interval
-1: Error
*/
WebRtc_Word32 VPMDeflickering::DetectFlicker()
{
/* Local variables */
WebRtc_UWord32 i;
WebRtc_Word32 freqEst; // (Q4) Frequency estimate to base detection upon
WebRtc_Word32 retVal = -1;
/* Sanity check for _meanBufferLength */
if (_meanBufferLength < 2)
{
/* Not possible to estimate frequency */
return(2);
}
/* Count zero crossings with a dead zone to be robust against noise.
* If the noise std is 2 pixel this corresponds to about 95% confidence interval.
*/
WebRtc_Word32 deadzone = (kZeroCrossingDeadzone << kMeanValueScaling); // Q4
WebRtc_Word32 meanOfBuffer = 0; // Mean value of mean value buffer
WebRtc_Word32 numZeros = 0; // Number of zeros that cross the deadzone
WebRtc_Word32 cntState = 0; // State variable for zero crossing regions
WebRtc_Word32 cntStateOld = 0; // Previous state variable for zero crossing regions
for (i = 0; i < _meanBufferLength; i++)
{
meanOfBuffer += _meanBuffer[i];
}
meanOfBuffer += (_meanBufferLength >> 1); // Rounding, not truncation
meanOfBuffer /= _meanBufferLength;
/* Count zero crossings */
cntStateOld = (_meanBuffer[0] >= (meanOfBuffer + deadzone));
cntStateOld -= (_meanBuffer[0] <= (meanOfBuffer - deadzone));
for (i = 1; i < _meanBufferLength; i++)
{
cntState = (_meanBuffer[i] >= (meanOfBuffer + deadzone));
cntState -= (_meanBuffer[i] <= (meanOfBuffer - deadzone));
if (cntStateOld == 0)
{
cntStateOld = -cntState;
}
if (((cntState + cntStateOld) == 0) && (cntState != 0))
{
numZeros++;
cntStateOld = cntState;
}
}
/* END count zero crossings */
/* Frequency estimation according to:
* freqEst = numZeros * frameRate / 2 / _meanBufferLength;
*
* Resolution is set to Q4
*/
freqEst = ((numZeros * 90000) << 3);
freqEst /= (_timestampBuffer[0] - _timestampBuffer[_meanBufferLength - 1]);
/* Translate frequency estimate to regions close to 100 and 120 Hz */
WebRtc_UWord8 freqState = 0; // Current translation state;
// (0) Not in interval,
// (1) Within valid interval,
// (2) Out of range
WebRtc_Word32 freqAlias = freqEst;
if (freqEst > kMinFrequencyToDetect)
{
WebRtc_UWord8 aliasState = 1;
while(freqState == 0)
{
/* Increase frequency */
freqAlias += (aliasState * _frameRate);
freqAlias += ((freqEst << 1) * (1 - (aliasState << 1)));
/* Compute state */
freqState = (abs(freqAlias - (100 << 4)) <= kFrequencyDeviation);
freqState += (abs(freqAlias - (120 << 4)) <= kFrequencyDeviation);
freqState += 2 * (freqAlias > ((120 << 4) + kFrequencyDeviation));
/* Switch alias state */
aliasState++;
aliasState &= 0x01;
}
}
/* Is frequency estimate within detection region? */
if (freqState == 1)
{
retVal = 1;
}else if (freqState == 0)
{
retVal = 2;
}else
{
retVal = 0;
}
return retVal;
}
} //namespace