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fix: skip black webcam warmup frames

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This commit is contained in:
EtienneLescot
2026-05-05 18:51:08 +02:00
parent 84484d6167
commit 38d727eb8e
3 changed files with 57 additions and 7 deletions
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electron/native/wgc-capture/src/main.cpp
+51 -6
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@@ -97,6 +97,31 @@ std::string jsonEscape(const std::string& value) {
return result;
}
bool hasVisibleBgraContent(const std::vector<BYTE>& frame) {
if (frame.size() < 4) {
return false;
}
uint64_t lumaTotal = 0;
BYTE maxLuma = 0;
const size_t pixelCount = frame.size() / 4;
const size_t step = std::max<size_t>(1, pixelCount / 4096);
size_t sampledPixels = 0;
for (size_t pixel = 0; pixel < pixelCount; pixel += step) {
const size_t offset = pixel * 4;
const BYTE b = frame[offset + 0];
const BYTE g = frame[offset + 1];
const BYTE r = frame[offset + 2];
const BYTE luma = static_cast<BYTE>((static_cast<uint16_t>(r) * 54 + static_cast<uint16_t>(g) * 183 + static_cast<uint16_t>(b) * 19) >> 8);
lumaTotal += luma;
maxLuma = std::max(maxLuma, luma);
sampledPixels += 1;
}
const uint64_t averageLuma = sampledPixels > 0 ? lumaTotal / sampledPixels : 0;
return maxLuma > 24 || averageLuma > 4;
}
bool findBool(const std::string& json, const std::string& key, bool fallback) {
auto pos = json.find("\"" + key + "\"");
if (pos == std::string::npos) {
@@ -432,6 +457,7 @@ int main(int argc, char* argv[]) {
std::vector<BYTE> latestWebcamFrame;
int latestWebcamWidth = 0;
int latestWebcamHeight = 0;
bool hasVisibleWebcamFrame = false;
session.setFrameCallback([&](ID3D11Texture2D* texture, int64_t timestampHns) {
(void)timestampHns;
@@ -468,10 +494,19 @@ int main(int argc, char* argv[]) {
{
std::scoped_lock lock(mutex);
if (webcamActive) {
webcamCapture.copyLatestFrame(latestWebcamFrame, latestWebcamWidth, latestWebcamHeight);
std::vector<BYTE> candidateWebcamFrame;
int candidateWebcamWidth = 0;
int candidateWebcamHeight = 0;
if (webcamCapture.copyLatestFrame(candidateWebcamFrame, candidateWebcamWidth, candidateWebcamHeight) &&
hasVisibleBgraContent(candidateWebcamFrame)) {
latestWebcamFrame = std::move(candidateWebcamFrame);
latestWebcamWidth = candidateWebcamWidth;
latestWebcamHeight = candidateWebcamHeight;
hasVisibleWebcamFrame = true;
}
}
const BgraFrameView webcamFrame{
latestWebcamFrame.empty() ? nullptr : latestWebcamFrame.data(),
hasVisibleWebcamFrame && !latestWebcamFrame.empty() ? latestWebcamFrame.data() : nullptr,
latestWebcamWidth,
latestWebcamHeight,
};
@@ -583,12 +618,22 @@ int main(int argc, char* argv[]) {
}
webcamActive = true;
const auto webcamDeadline = std::chrono::steady_clock::now() + std::chrono::seconds(3);
while (std::chrono::steady_clock::now() < webcamDeadline &&
!webcamCapture.copyLatestFrame(latestWebcamFrame, latestWebcamWidth, latestWebcamHeight)) {
while (std::chrono::steady_clock::now() < webcamDeadline && !hasVisibleWebcamFrame) {
std::vector<BYTE> candidateWebcamFrame;
int candidateWebcamWidth = 0;
int candidateWebcamHeight = 0;
if (webcamCapture.copyLatestFrame(candidateWebcamFrame, candidateWebcamWidth, candidateWebcamHeight) &&
hasVisibleBgraContent(candidateWebcamFrame)) {
latestWebcamFrame = std::move(candidateWebcamFrame);
latestWebcamWidth = candidateWebcamWidth;
latestWebcamHeight = candidateWebcamHeight;
hasVisibleWebcamFrame = true;
break;
}
std::this_thread::sleep_for(std::chrono::milliseconds(20));
}
if (latestWebcamFrame.empty()) {
std::cerr << "WARNING: Native webcam started but no frame was available before screen capture"
if (!hasVisibleWebcamFrame) {
std::cerr << "WARNING: Native webcam started but no visible frame was available before screen capture"
<< std::endl;
}
}