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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qv4l2memorytransfer_p.h"
#include "qv4l2filedescriptor_p.h"
#include <qloggingcategory.h>
#include <qdebug.h>
#include <sys/mman.h>
#include <optional>
QT_BEGIN_NAMESPACE
static Q_LOGGING_CATEGORY(qLcV4L2MemoryTransfer, "qt.multimedia.ffmpeg.v4l2camera.memorytransfer");
namespace {
v4l2_buffer makeV4l2Buffer(quint32 memoryType, quint32 index = 0)
{
v4l2_buffer buf = {};
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = memoryType;
buf.index = index;
return buf;
}
class UserPtrMemoryTransfer : public QV4L2MemoryTransfer
{
public:
static QV4L2MemoryTransferUPtr create(QV4L2FileDescriptorPtr fileDescriptor, quint32 imageSize)
{
quint32 buffersCount = 2;
if (!fileDescriptor->requestBuffers(V4L2_MEMORY_USERPTR, buffersCount)) {
qCWarning(qLcV4L2MemoryTransfer) << "Cannot request V4L2_MEMORY_USERPTR buffers";
return {};
}
std::unique_ptr<UserPtrMemoryTransfer> result(
new UserPtrMemoryTransfer(std::move(fileDescriptor), buffersCount, imageSize));
return result->enqueueBuffers() ? std::move(result) : nullptr;
}
std::optional<Buffer> dequeueBuffer() override
{
auto v4l2Buffer = makeV4l2Buffer(V4L2_MEMORY_USERPTR);
if (!fileDescriptor().call(VIDIOC_DQBUF, &v4l2Buffer))
return {};
Q_ASSERT(v4l2Buffer.index < m_byteArrays.size());
Q_ASSERT(!m_byteArrays[v4l2Buffer.index].isEmpty());
return Buffer{ v4l2Buffer, std::move(m_byteArrays[v4l2Buffer.index]) };
}
bool enqueueBuffer(quint32 index) override
{
Q_ASSERT(index < m_byteArrays.size());
Q_ASSERT(m_byteArrays[index].isEmpty());
auto buf = makeV4l2Buffer(V4L2_MEMORY_USERPTR, index);
static_assert(sizeof(decltype(buf.m.userptr)) == sizeof(size_t), "Not compatible sizes");
m_byteArrays[index] = QByteArray(static_cast<int>(m_imageSize), Qt::Uninitialized);
buf.m.userptr = (decltype(buf.m.userptr))m_byteArrays[index].data();
buf.length = m_byteArrays[index].size();
if (!fileDescriptor().call(VIDIOC_QBUF, &buf)) {
qWarning() << "Couldn't add V4L2 buffer" << errno << strerror(errno) << index;
return false;
}
return true;
}
quint32 buffersCount() const override { return static_cast<quint32>(m_byteArrays.size()); }
private:
UserPtrMemoryTransfer(QV4L2FileDescriptorPtr fileDescriptor, quint32 buffersCount,
quint32 imageSize)
: QV4L2MemoryTransfer(std::move(fileDescriptor)),
m_imageSize(imageSize),
m_byteArrays(buffersCount)
{
}
private:
quint32 m_imageSize;
std::vector<QByteArray> m_byteArrays;
};
class MMapMemoryTransfer : public QV4L2MemoryTransfer
{
public:
struct MemorySpan
{
void *data = nullptr;
size_t size = 0;
bool inQueue = false;
};
static QV4L2MemoryTransferUPtr create(QV4L2FileDescriptorPtr fileDescriptor)
{
quint32 buffersCount = 2;
if (!fileDescriptor->requestBuffers(V4L2_MEMORY_MMAP, buffersCount)) {
qCWarning(qLcV4L2MemoryTransfer) << "Cannot request V4L2_MEMORY_MMAP buffers";
return {};
}
std::unique_ptr<MMapMemoryTransfer> result(
new MMapMemoryTransfer(std::move(fileDescriptor)));
return result->init(buffersCount) ? std::move(result) : nullptr;
}
bool init(quint32 buffersCount)
{
for (quint32 index = 0; index < buffersCount; ++index) {
auto buf = makeV4l2Buffer(V4L2_MEMORY_MMAP, index);
if (!fileDescriptor().call(VIDIOC_QUERYBUF, &buf)) {
qWarning() << "Can't map buffer" << index;
return false;
}
auto mappedData = mmap(nullptr, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED,
fileDescriptor().get(), buf.m.offset);
if (mappedData == MAP_FAILED) {
qWarning() << "mmap failed" << index << buf.length << buf.m.offset;
return false;
}
m_spans.push_back(MemorySpan{ mappedData, buf.length, false });
}
m_spans.shrink_to_fit();
return enqueueBuffers();
}
~MMapMemoryTransfer() override
{
for (const auto &span : m_spans)
munmap(span.data, span.size);
}
std::optional<Buffer> dequeueBuffer() override
{
auto v4l2Buffer = makeV4l2Buffer(V4L2_MEMORY_MMAP);
if (!fileDescriptor().call(VIDIOC_DQBUF, &v4l2Buffer))
return {};
const auto index = v4l2Buffer.index;
Q_ASSERT(index < m_spans.size());
auto &span = m_spans[index];
Q_ASSERT(span.inQueue);
span.inQueue = false;
return Buffer{ v4l2Buffer,
QByteArray(reinterpret_cast<const char *>(span.data), span.size) };
}
bool enqueueBuffer(quint32 index) override
{
Q_ASSERT(index < m_spans.size());
Q_ASSERT(!m_spans[index].inQueue);
auto buf = makeV4l2Buffer(V4L2_MEMORY_MMAP, index);
if (!fileDescriptor().call(VIDIOC_QBUF, &buf))
return false;
m_spans[index].inQueue = true;
return true;
}
quint32 buffersCount() const override { return static_cast<quint32>(m_spans.size()); }
private:
using QV4L2MemoryTransfer::QV4L2MemoryTransfer;
private:
std::vector<MemorySpan> m_spans;
};
} // namespace
QV4L2MemoryTransfer::QV4L2MemoryTransfer(QV4L2FileDescriptorPtr fileDescriptor)
: m_fileDescriptor(std::move(fileDescriptor))
{
Q_ASSERT(m_fileDescriptor);
Q_ASSERT(!m_fileDescriptor->streamStarted());
}
QV4L2MemoryTransfer::~QV4L2MemoryTransfer()
{
Q_ASSERT(!m_fileDescriptor->streamStarted()); // to avoid possible corruptions
}
bool QV4L2MemoryTransfer::enqueueBuffers()
{
for (quint32 i = 0; i < buffersCount(); ++i)
if (!enqueueBuffer(i))
return false;
return true;
}
QV4L2MemoryTransferUPtr makeUserPtrMemoryTransfer(QV4L2FileDescriptorPtr fileDescriptor,
quint32 imageSize)
{
return UserPtrMemoryTransfer::create(std::move(fileDescriptor), imageSize);
}
QV4L2MemoryTransferUPtr makeMMapMemoryTransfer(QV4L2FileDescriptorPtr fileDescriptor)
{
return MMapMemoryTransfer::create(std::move(fileDescriptor));
}
QT_END_NAMESPACE
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