MJPEG acceleration for V4L2

content/common/gpu/media/v4l2_jpeg_decode_accelerator.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <linux/videodev2.h>
+#include <sys/mman.h>
+
+#include "base/bind.h"
+#include "base/thread_task_runner_handle.h"
+#include "content/common/gpu/media/v4l2_jpeg_decode_accelerator.h"
+
+#define IOCTL_OR_ERROR_RETURN_VALUE(type, arg, value, type_name)      \
+  do {                                                                \
+    if (device_->Ioctl(type, arg) != 0) {                             \
+      PLOG(ERROR) << __func__ << "(): ioctl() failed: " << type_name; \
+      return value;                                                   \
+    }                                                                 \
+  } while (0)
+
+#define IOCTL_OR_ERROR_RETURN(type, arg) \
+  IOCTL_OR_ERROR_RETURN_VALUE(type, arg, ((void)0), #type)
+
+#define IOCTL_OR_ERROR_RETURN_FALSE(type, arg) \
+  IOCTL_OR_ERROR_RETURN_VALUE(type, arg, false, #type)
+
+#define IOCTL_OR_LOG_ERROR(type, arg)                             \
+  do {                                                            \
+    if (device_->Ioctl(type, arg) != 0)                           \
+      PLOG(ERROR) << __func__ << "(): ioctl() failed: " << #type; \
+  } while (0)
+
+namespace content {
+
+V4L2JpegDecodeAccelerator::BufferRecord::BufferRecord()
+    : address(nullptr), length(0), at_device(false) {
+}
+
+V4L2JpegDecodeAccelerator::BufferRecord::~BufferRecord() {
+}
+
+V4L2JpegDecodeAccelerator::JobRecord::JobRecord(
+    media::BitstreamBuffer bitstream_buffer,
+    scoped_refptr<media::VideoFrame> video_frame)
+    : bitstream_buffer(bitstream_buffer), out_frame(video_frame) {
+}
+
+V4L2JpegDecodeAccelerator::JobRecord::~JobRecord() {
+}
+
+V4L2JpegDecodeAccelerator::V4L2JpegDecodeAccelerator(
+    const scoped_refptr<V4L2Device>& device,
+    const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner)
+    : recreate_input_buffers_pending_(false),
+      recreate_output_buffers_pending_(false),
+      child_task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      io_task_runner_(io_task_runner),
+      client_(nullptr),
+      device_(device),
+      decoder_thread_("V4L2JpegDecodeThread"),
+      device_poll_thread_("V4L2JpegDecodeDevicePollThread"),
+      input_streamon_(false),
+      output_streamon_(false),
+      weak_factory_(this) {
+}
+
+V4L2JpegDecodeAccelerator::~V4L2JpegDecodeAccelerator() {
+  DCHECK(child_task_runner_->BelongsToCurrentThread());
+
+  if (decoder_thread_.IsRunning()) {
+    decoder_task_runner_->PostTask(
+        FROM_HERE, base::Bind(&V4L2JpegDecodeAccelerator::DestroyTask,
+                              base::Unretained(this)));
+    decoder_thread_.Stop();
+  }
+  weak_factory_.InvalidateWeakPtrs();
+  DCHECK(!device_poll_thread_.IsRunning());
+}
+
+void V4L2JpegDecodeAccelerator::DestroyTask() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  while (!input_jobs_.empty()) input_jobs_.pop();
+  while (!running_jobs_.empty()) running_jobs_.pop();
+
+  // Stop streaming and the device_poll_thread_.
+  StopDevicePoll();
+
+  DestroyInputBuffers();
+  DestroyOutputBuffers();
+}
+
+void V4L2JpegDecodeAccelerator::NotifyError(int32_t bitstream_buffer_id,
+                                            Error error) {
+  DCHECK(child_task_runner_->BelongsToCurrentThread());
+  LOG(ERROR) << "Notifying of error " << error << " for buffer id "
+             << bitstream_buffer_id;
+  client_->NotifyError(bitstream_buffer_id, error);
+}
+
+void V4L2JpegDecodeAccelerator::PostNotifyError(
+    int32_t bitstream_buffer_id,
+    Error error) {
+  child_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&V4L2JpegDecodeAccelerator::NotifyError,
+                 weak_factory_.GetWeakPtr(), bitstream_buffer_id, error));
+}
+
+bool V4L2JpegDecodeAccelerator::Initialize(Client* client) {
+  DCHECK(child_task_runner_->BelongsToCurrentThread());
+
+  // Capabilities check.
+  struct v4l2_capability caps;
+  const __u32 kCapsRequired = V4L2_CAP_STREAMING | V4L2_CAP_VIDEO_M2M;
+  IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QUERYCAP, &caps);
+  if ((caps.capabilities & kCapsRequired) != kCapsRequired) {
+    LOG(ERROR) << "Initialize(): VIDIOC_QUERYCAP, caps check failed: 0x"
+               << std::hex << caps.capabilities;
+    return false;
+  }
+
+  if (!decoder_thread_.Start()) {
+    LOG(ERROR) << "Initialize(): decoder thread failed to start";
+    return false;
+  }
+  client_ = client;
+  decoder_task_runner_ = decoder_thread_.task_runner();
+
+  decoder_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&V4L2JpegDecodeAccelerator::StartDevicePoll,
+                            base::Unretained(this)));
+
+  DVLOG(1) << "V4L2JpegDecodeAccelerator initialized.";
+  return true;
+}
+
+void V4L2JpegDecodeAccelerator::Decode(
+    const media::BitstreamBuffer& bitstream_buffer,
+    const scoped_refptr<media::VideoFrame>& video_frame) {
+  DVLOG(1) << "Decode(): input_id=" << bitstream_buffer.id()
+           << ", size=" << bitstream_buffer.size();
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+  DCHECK_EQ(video_frame->format(), media::VideoFrame::I420);
+
+  scoped_ptr<JobRecord> job_record(
+      new JobRecord(bitstream_buffer, video_frame));
+
+  decoder_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&V4L2JpegDecodeAccelerator::DecodeTask,
+                            base::Unretained(this), base::Passed(&job_record)));
+}
+
+void V4L2JpegDecodeAccelerator::DecodeTask(scoped_ptr<JobRecord> job_record) {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  job_record->shm.reset(
+      new base::SharedMemory(job_record->bitstream_buffer.handle(), true));
+  if (!job_record->shm->Map(job_record->bitstream_buffer.size())) {
+    PLOG(ERROR) << "Decode(): could not map bitstream_buffer";
+    PostNotifyError(job_record->bitstream_buffer.id(), UNREADABLE_INPUT);
+    return;
+  }
+  input_jobs_.push(make_linked_ptr(job_record.release()));
+  ServiceDeviceTask();
+}
+
+int V4L2JpegDecodeAccelerator::InputBufferQueuedCount() {
+  return input_buffer_map_.size() - free_input_buffers_.size();
+}
+
+int V4L2JpegDecodeAccelerator::OutputBufferQueuedCount() {
+  return output_buffer_map_.size() - free_output_buffers_.size();
+}
+
+bool V4L2JpegDecodeAccelerator::ShouldRecreateInputBuffers() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  if (input_jobs_.empty())
+    return false;
+
+  linked_ptr<JobRecord> job_record = input_jobs_.front();
+  // Check input buffer size is enough
+  return (input_buffer_map_.empty() ||
+      job_record->bitstream_buffer.size() > input_buffer_map_.front().length);
+}
+
+bool V4L2JpegDecodeAccelerator::ShouldRecreateOutputBuffers() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  if (input_jobs_.empty())
+    return false;
+
+  linked_ptr<JobRecord> job_record = input_jobs_.front();
+  // Check image resolution is the same as previous.
+  if (job_record->out_frame->coded_size() != image_coded_size_) {
+    size_t frame_size = media::VideoFrame::AllocationSize(
+        job_record->out_frame->format(), job_record->out_frame->coded_size());
+    if (output_buffer_map_.empty() ||
+        frame_size > output_buffer_map_.front().length) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool V4L2JpegDecodeAccelerator::CreateBuffersIfNecessary() {
+  DVLOG(3) << __func__;
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+
+  recreate_input_buffers_pending_ = ShouldRecreateInputBuffers();
+  recreate_output_buffers_pending_ = ShouldRecreateOutputBuffers();
+  if (!recreate_input_buffers_pending_ && !recreate_output_buffers_pending_)
+    return true;
+
+  // If queues are not empty, we should wait until pending frames finish.
+  if (InputBufferQueuedCount() || OutputBufferQueuedCount())
+    return true;
+
+  if (input_streamon_ || output_streamon_) {
+    if (!StopDevicePoll()) {
+      LOG(ERROR) << "Stop device poll thread failed when recreating buffers.";
+      return false;
+    }
+    if (recreate_input_buffers_pending_)
+      DestroyInputBuffers();
+
+    if (recreate_output_buffers_pending_)
+      DestroyOutputBuffers();
+  }
+
+  if (recreate_input_buffers_pending_ && !CreateInputBuffers()) {
+    LOG(ERROR) << "Create input buffers failed.";
+    return false;
+  }
+  if (recreate_output_buffers_pending_ && !CreateOutputBuffers()) {
+    LOG(ERROR) << "Create output buffers failed.";
+    return false;
+  }
+
+  if (!device_poll_thread_.IsRunning())
+    StartDevicePoll();
+  return true;
+}
+
+bool V4L2JpegDecodeAccelerator::CreateInputBuffers() {
+  DVLOG(3) << __func__;
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  DCHECK(!input_streamon_);
+  DCHECK(!input_jobs_.empty());
+  linked_ptr<JobRecord> job_record = input_jobs_.front();
+  // Reserve twice size to avoid recreating input buffer frequently.
+  size_t reserve_size = job_record->bitstream_buffer.size() * 2;
+
+  struct v4l2_format format;
+  memset(&format, 0, sizeof(format));
+  format.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+  format.fmt.pix.width = job_record->out_frame->coded_size().width();
+  format.fmt.pix.height = job_record->out_frame->coded_size().height();
+  format.fmt.pix.pixelformat = V4L2_PIX_FMT_JPEG;
+  format.fmt.pix.sizeimage = reserve_size;
+  format.fmt.pix.field = V4L2_FIELD_ANY;
+  IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_S_FMT, &format);
+
+  struct v4l2_requestbuffers reqbufs;
+  memset(&reqbufs, 0, sizeof(reqbufs));
+  reqbufs.count = kBufferCount;
+  reqbufs.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+  reqbufs.memory = V4L2_MEMORY_MMAP;
+  IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_REQBUFS, &reqbufs);
+
+  DCHECK(input_buffer_map_.empty());
+  input_buffer_map_.resize(reqbufs.count);
+
+  for (size_t i = 0; i < input_buffer_map_.size(); ++i) {
+    free_input_buffers_.push_back(i);
+
+    struct v4l2_buffer buffer;
+    memset(&buffer, 0, sizeof(buffer));
+    buffer.index = i;
+    buffer.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+    buffer.memory = V4L2_MEMORY_MMAP;
+    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QUERYBUF, &buffer);
+    void* address = device_->Mmap(NULL, buffer.length, PROT_READ | PROT_WRITE,
+                                  MAP_SHARED, buffer.m.offset);
+    if (address == MAP_FAILED) {
+      PLOG(ERROR) << "CreateInputBuffers(): mmap() failed";
+      PostNotifyError(job_record->bitstream_buffer.id(),
+                      media::JpegDecodeAccelerator::PLATFORM_FAILURE);
+      return false;
+    }
+    input_buffer_map_[i].address = address;
+    input_buffer_map_[i].length = buffer.length;
+  }
+  recreate_input_buffers_pending_ = false;
+
+  return true;
+}
+
+bool V4L2JpegDecodeAccelerator::CreateOutputBuffers() {
+  DVLOG(3) << __func__;
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  DCHECK(!output_streamon_);
+  DCHECK(!input_jobs_.empty());
+  linked_ptr<JobRecord> job_record = input_jobs_.front();
+
+  size_t frame_size = media::VideoFrame::AllocationSize(
+      media::VideoFrame::I420, job_record->out_frame->coded_size());
+  struct v4l2_format format;
+  memset(&format, 0, sizeof(format));
+  format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+  format.fmt.pix.width = job_record->out_frame->coded_size().width();
+  format.fmt.pix.height = job_record->out_frame->coded_size().height();
+  format.fmt.pix.sizeimage = frame_size;
+  format.fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420;
+  format.fmt.pix.field = V4L2_FIELD_ANY;
+  IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_S_FMT, &format);
+
+  struct v4l2_requestbuffers reqbufs;
+  memset(&reqbufs, 0, sizeof(reqbufs));
+  reqbufs.count = kBufferCount;
+  reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+  reqbufs.memory = V4L2_MEMORY_MMAP;
+  IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_REQBUFS, &reqbufs);
+
+  DCHECK(output_buffer_map_.empty());
+  output_buffer_map_.resize(reqbufs.count);
+
+  for (size_t i = 0; i < output_buffer_map_.size(); ++i) {
+    free_output_buffers_.push_back(i);
+
+    struct v4l2_buffer buffer;
+    memset(&buffer, 0, sizeof(buffer));
+    buffer.index = i;
+    buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+    buffer.memory = V4L2_MEMORY_MMAP;
+    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QUERYBUF, &buffer);
+    void* address = device_->Mmap(NULL, buffer.length, PROT_READ | PROT_WRITE,
+                                  MAP_SHARED, buffer.m.offset);
+    if (address == MAP_FAILED) {
+      PLOG(ERROR) << "CreateOutputBuffers(): mmap() failed";
+      PostNotifyError(job_record->bitstream_buffer.id(),
+                      media::JpegDecodeAccelerator::PLATFORM_FAILURE);
+      return false;
+    }
+    output_buffer_map_[i].address = address;
+    output_buffer_map_[i].length = buffer.length;
+  }
+  image_coded_size_ = job_record->out_frame->coded_size();
+  recreate_output_buffers_pending_ = false;
+
+  return true;
+}
+
+void V4L2JpegDecodeAccelerator::DestroyInputBuffers() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  DCHECK(!input_streamon_);
+
+  for (size_t buf = 0; buf < input_buffer_map_.size(); ++buf) {
+    BufferRecord& input_record = input_buffer_map_[buf];
+    device_->Munmap(input_record.address, input_record.length);
+  }
+
+  struct v4l2_requestbuffers reqbufs;
+  memset(&reqbufs, 0, sizeof(reqbufs));
+  reqbufs.count = 0;
+  reqbufs.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+  reqbufs.memory = V4L2_MEMORY_MMAP;
+  IOCTL_OR_LOG_ERROR(VIDIOC_REQBUFS, &reqbufs);
+
+  input_buffer_map_.clear();
+  free_input_buffers_.clear();
+}
+
+void V4L2JpegDecodeAccelerator::DestroyOutputBuffers() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  DCHECK(!output_streamon_);
+
+  for (size_t buf = 0; buf < output_buffer_map_.size(); ++buf) {
+    BufferRecord& output_record = output_buffer_map_[buf];
+    device_->Munmap(output_record.address, output_record.length);
+  }
+
+  struct v4l2_requestbuffers reqbufs;
+  memset(&reqbufs, 0, sizeof(reqbufs));
+  reqbufs.count = 0;
+  reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+  reqbufs.memory = V4L2_MEMORY_MMAP;
+  IOCTL_OR_LOG_ERROR(VIDIOC_REQBUFS, &reqbufs);
+
+  output_buffer_map_.clear();
+  free_output_buffers_.clear();
+}
+
+void V4L2JpegDecodeAccelerator::DevicePollTask() {
+  DCHECK(device_poll_task_runner_->BelongsToCurrentThread());
+
+  bool event_pending;
+  if (!device_->Poll(true, &event_pending)) {
+    PostNotifyError(-1, media::JpegDecodeAccelerator::PLATFORM_FAILURE);
+    return;
+  }
+
+  // All processing should happen on ServiceDeviceTask(), since we shouldn't
+  // touch decoder state from this thread.
+  decoder_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&V4L2JpegDecodeAccelerator::ServiceDeviceTask,
+                            base::Unretained(this)));
+}
+
+void V4L2JpegDecodeAccelerator::ServiceDeviceTask() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  // ServiceDeviceTask() should only ever be scheduled from DevicePollTask(),
+  // so either:
+  // * device_poll_thread_ is running normally
+  // * device_poll_thread_ scheduled us, but then a DestroyTask() shut it down,
+  //   in which case we should early-out.
+  if (!device_poll_thread_.IsRunning())
+    return;
+
+  if (InputBufferQueuedCount() > 0 || OutputBufferQueuedCount() > 0)
+    Dequeue();
+  if (!CreateBuffersIfNecessary()) return;
+
+  // Stop enqueue input record when input/output buffers are required to

[wuchengli, 2015/06/26 23:42:48]

s/Stop enqueue/Do not queue/

"Stop enqueuing" means an action has been done and queuing has stopped because
of the action from this point. In fact, no action is done. The code simply not
to queue an input record.

[henryhsu, 2015/06/29 05:20:52]

Done.

+  // re-create until all pending frames are handled by device.
+  // Output record can be enqueued in this case since the number of

[wuchengli, 2015/06/26 23:42:48]

This is not the reason why output can be queued. The new input record will have
new resolution. The new output record will have the same resolution as the last
queued DecodeTask.

// Output record can be enqueued because the output coded sizes of the frames
currently in the pipeline are all the same.

[henryhsu, 2015/06/29 05:20:52]

Done.

+  // enqueued output record may be smaller than the number of enqueued
+  // input record.
+  if (!recreate_input_buffers_pending_ && !recreate_output_buffers_pending_)
+    EnqueueInput();
+  EnqueueOutput();
+
+  if (!device_->ClearDevicePollInterrupt()) return;
+
+  if (InputBufferQueuedCount() > 0 || OutputBufferQueuedCount() > 0) {
+    device_poll_task_runner_->PostTask(
+        FROM_HERE, base::Bind(&V4L2JpegDecodeAccelerator::DevicePollTask,
+                              base::Unretained(this)));
+  }
+
+  DVLOG(2) << __func__ << ": buffer counts: INPUT["
+           << input_jobs_.size() << "] => DEVICE["
+           << free_input_buffers_.size() << "+"
+           << InputBufferQueuedCount() << "/"
+           << input_buffer_map_.size() << "->"
+           << free_output_buffers_.size() << "+"
+           << OutputBufferQueuedCount() << "/"
+           << output_buffer_map_.size() << "]";
+}
+
+void V4L2JpegDecodeAccelerator::EnqueueInput() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  while (!input_jobs_.empty() && !free_input_buffers_.empty()) {
+    if (!EnqueueInputRecord())
+      return;
+  }
+  if (!input_streamon_ && InputBufferQueuedCount()) {

[wuchengli, 2015/06/26 23:42:48]

Why this part is moved back here?

[henryhsu, 2015/06/29 03:35:02]

Pawel said it depends on different kernel. This patch
https://chromium-review.googlesource.com/#/c/218105/ allows stream on before
qbuf.
I think we should check stream_on in Enqueue function to be compatible for all
kernel versions.

+    __u32 type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+    IOCTL_OR_ERROR_RETURN(VIDIOC_STREAMON, &type);
+    input_streamon_ = true;
+  }
+}
+
+void V4L2JpegDecodeAccelerator::EnqueueOutput() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  while (!free_output_buffers_.empty()) {
+    if (!EnqueueOutputRecord())
+      return;
+  }
+  if (!output_streamon_ && OutputBufferQueuedCount()) {
+    __u32 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+    IOCTL_OR_ERROR_RETURN(VIDIOC_STREAMON, &type);
+    output_streamon_ = true;
+  }
+}
+
+void V4L2JpegDecodeAccelerator::Dequeue() {
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+
+  // Dequeue completed input (VIDEO_OUTPUT) buffers,
+  // and recycle to the free list.
+  struct v4l2_buffer dqbuf;
+  while (InputBufferQueuedCount() > 0) {
+    DCHECK(input_streamon_);
+    memset(&dqbuf, 0, sizeof(dqbuf));
+    dqbuf.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+    dqbuf.memory = V4L2_MEMORY_MMAP;
+    if (device_->Ioctl(VIDIOC_DQBUF, &dqbuf) != 0) {
+      if (errno == EAGAIN) {
+        // EAGAIN if we're just out of buffers to dequeue.
+        break;
+      }
+      PLOG(ERROR) << "ioctl() failed: VIDIOC_DQBUF";
+      PostNotifyError(dqbuf.index,
+                      media::JpegDecodeAccelerator::PLATFORM_FAILURE);
+      return;
+    }
+    BufferRecord& input_record = input_buffer_map_[dqbuf.index];
+    DCHECK(input_record.at_device);
+    input_record.at_device = false;
+    free_input_buffers_.push_back(dqbuf.index);
+  }
+
+  // Dequeue completed output (VIDEO_CAPTURE) buffers, recycle to the free list.
+  // Return the finished buffer to the client via the job ready callback.
+  while (OutputBufferQueuedCount() > 0) {
+    DCHECK(output_streamon_);
+    memset(&dqbuf, 0, sizeof(dqbuf));
+    dqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+    dqbuf.memory = V4L2_MEMORY_MMAP;
+    if (device_->Ioctl(VIDIOC_DQBUF, &dqbuf) != 0) {
+      if (errno == EAGAIN) {
+        // EAGAIN if we're just out of buffers to dequeue.
+        break;
+      }
+      PLOG(ERROR) << "ioctl() failed: VIDIOC_DQBUF";
+      PostNotifyError(dqbuf.index,
+                      media::JpegDecodeAccelerator::PLATFORM_FAILURE);
+      return;
+    }
+    BufferRecord& output_record = output_buffer_map_[dqbuf.index];
+    DCHECK(output_record.at_device);
+    output_record.at_device = false;
+    free_output_buffers_.push_back(dqbuf.index);
+
+    // Jobs are always processed in FIFO order.
+    DCHECK(!running_jobs_.empty());
+    linked_ptr<JobRecord> job_record = running_jobs_.front();
+    running_jobs_.pop();
+
+    memcpy(job_record->out_frame->data(media::VideoFrame::kYPlane),
+           output_record.address, output_record.length);
+
+    DVLOG(3) << "Decoding finished, returning frame, id="
+             << job_record->bitstream_buffer.id();
+
+    client_->VideoFrameReady(job_record->bitstream_buffer.id());
+  }
+}
+
+bool V4L2JpegDecodeAccelerator::EnqueueInputRecord() {
+  DCHECK(!input_jobs_.empty());
+  DCHECK(!free_input_buffers_.empty());
+
+  // Enqueue an input (VIDEO_OUTPUT) buffer for an input video frame.
+  linked_ptr<JobRecord> job_record = input_jobs_.front();
+  input_jobs_.pop();
+  const int index = free_input_buffers_.back();
+  BufferRecord& input_record = input_buffer_map_[index];
+  DCHECK(!input_record.at_device);
+
+  struct v4l2_buffer qbuf;
+  memset(&qbuf, 0, sizeof(qbuf));
+  memcpy(input_record.address, job_record->shm->memory(),
+         job_record->bitstream_buffer.size());
+  qbuf.index = index;
+  qbuf.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+  qbuf.memory = V4L2_MEMORY_MMAP;
+  IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QBUF, &qbuf);
+  input_record.at_device = true;
+  running_jobs_.push(job_record);
+  free_input_buffers_.pop_back();
+
+  DVLOG(3) << __func__ << ": enqueued frame id="
+           << job_record->bitstream_buffer.id() << " to device.";
+  return true;
+}
+
+bool V4L2JpegDecodeAccelerator::EnqueueOutputRecord() {
+  DCHECK(!free_output_buffers_.empty());
+
+  // Enqueue an output (VIDEO_CAPTURE) buffer.
+  const int index = free_output_buffers_.back();
+  BufferRecord& output_record = output_buffer_map_[index];
+  DCHECK(!output_record.at_device);
+  struct v4l2_buffer qbuf;
+  memset(&qbuf, 0, sizeof(qbuf));
+  qbuf.index = index;
+  qbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+  qbuf.memory = V4L2_MEMORY_MMAP;
+  IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QBUF, &qbuf);
+  output_record.at_device = true;
+  free_output_buffers_.pop_back();
+  return true;
+}
+
+void V4L2JpegDecodeAccelerator::StartDevicePoll() {
+  DVLOG(3) << __func__ << ": starting device poll";
+  DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+  DCHECK(!device_poll_thread_.IsRunning());
+
+  if (!device_poll_thread_.Start()) {
+    LOG(ERROR) << "StartDevicePoll(): Device thread failed to start";
+    PostNotifyError(-1, media::JpegDecodeAccelerator::PLATFORM_FAILURE);
+    return;
+  }
+  device_poll_task_runner_ = device_poll_thread_.task_runner();
+}
+
+bool V4L2JpegDecodeAccelerator::StopDevicePoll() {
+  DVLOG(3) << __func__ << ": stopping device poll";
+  if (decoder_thread_.IsRunning())
+    DCHECK(decoder_task_runner_->BelongsToCurrentThread());
+
+  // Signal the DevicePollTask() to stop, and stop the device poll thread.
+  if (!device_->SetDevicePollInterrupt()) {
+    LOG(ERROR) << "StopDevicePoll(): SetDevicePollInterrupt failed.";
+    PostNotifyError(-1, media::JpegDecodeAccelerator::PLATFORM_FAILURE);
+    return false;
+  }
+
+  device_poll_thread_.Stop();
+
+  // Clear the interrupt now, to be sure.
+  if (!device_->ClearDevicePollInterrupt())
+    return false;
+
+  if (input_streamon_) {
+    __u32 type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_STREAMOFF, &type);
+    input_streamon_ = false;
+  }
+
+  if (output_streamon_) {
+    __u32 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_STREAMOFF, &type);
+    output_streamon_ = false;
+  }
+
+  free_input_buffers_.clear();
+  for (size_t i = 0; i < input_buffer_map_.size(); ++i) {
+    BufferRecord& input_record = input_buffer_map_[i];
+    input_record.at_device = false;
+    free_input_buffers_.push_back(i);
+  }
+
+  free_output_buffers_.clear();
+  for (size_t i = 0; i < output_buffer_map_.size(); ++i) {
+    BufferRecord& output_record = output_buffer_map_[i];
+    output_record.at_device = false;
+    free_output_buffers_.push_back(i);
+  }
+
+  return true;
+}
+
+}  // namespace content