Linux Video Capture: Add V4L2VideoCaptureDelegate{Single,Multi}Plane.

media/video/capture/linux/v4l2_capture_delegate.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// 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 "media/video/capture/linux/video_capture_device_linux.h"
+#include "media/video/capture/linux/v4l2_capture_delegate.h"
 
-#include <errno.h>
-#include <fcntl.h>
 #include <poll.h>
-#if defined(OS_OPENBSD)
-#include <sys/videoio.h>
-#else
-#include <linux/videodev2.h>
-#endif
+#include <sys/fcntl.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 
-#include <list>
-#include <string>
-
 #include "base/bind.h"
 #include "base/files/file_enumerator.h"
-#include "base/files/scoped_file.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/strings/stringprintf.h"
+#include "media/base/bind_to_current_loop.h"
+#include "media/video/capture/linux/v4l2_capture_delegate_multi_plane.h"
+#include "media/video/capture/linux/v4l2_capture_delegate_single_plane.h"
+#include "media/video/capture/linux/video_capture_device_linux.h"
 
 namespace media {
 
-#define GET_V4L2_FOURCC_CHAR(a, index) ((char)( ((a) >> (8 * index)) & 0xff))
-
 // Desired number of video buffers to allocate. The actual number of allocated
 // buffers by v4l2 driver can be higher or lower than this number.
 // kNumVideoBuffers should not be too small, or Chrome may not return enough
 // buffers back to driver in time.
 const uint32 kNumVideoBuffers = 4;
 // Timeout in milliseconds v4l2_thread_ blocks waiting for a frame from the hw.
-enum { kCaptureTimeoutMs = 200 };
+const int kCaptureTimeoutMs = 200;
 // The number of continuous timeouts tolerated before treated as error.
-enum { kContinuousTimeoutLimit = 10 };
-// MJPEG is preferred if the width or height is larger than this.
-enum { kMjpegWidth = 640 };
-enum { kMjpegHeight = 480 };
+const int kContinuousTimeoutLimit = 10;
+// MJPEG is preferred if the requested width or height is larger than this.
+const int kMjpegWidth = 640;
+const int kMjpegHeight = 480;
 // Typical framerate, in fps
-enum { kTypicalFramerate = 30 };
+const int kTypicalFramerate = 30;
 
-class VideoCaptureDeviceLinux::V4L2CaptureDelegate
-    : public base::RefCountedThreadSafe<V4L2CaptureDelegate>{
- public:
-  V4L2CaptureDelegate(
-      const Name& device_name,
-      const scoped_refptr<base::SingleThreadTaskRunner>  v4l2_task_runner,
-      int power_line_frequency);
-
-  void AllocateAndStart(int width,
-                        int height,
-                        float frame_rate,
-                        scoped_ptr<Client> client);
-  void StopAndDeAllocate();
-  void SetRotation(int rotation);
-  bool DeAllocateVideoBuffers();
-
- private:
-  // Buffers used to receive captured frames from v4l2.
-  struct Buffer {
-    Buffer() : start(0), length(0) {}
-    void* start;
-    size_t length;
-  };
-
-  friend class base::RefCountedThreadSafe<V4L2CaptureDelegate>;
-   ~V4L2CaptureDelegate();
-
-  void DoCapture();
-  bool AllocateVideoBuffers();
-  void SetErrorState(const std::string& reason);
-
-  const scoped_refptr<base::SingleThreadTaskRunner> v4l2_task_runner_;
-
-  bool is_capturing_;
-  scoped_ptr<VideoCaptureDevice::Client> client_;
-  const Name device_name_;
-  base::ScopedFD device_fd_;  // File descriptor for the opened camera device.
-  Buffer* buffer_pool_;
-  int buffer_pool_size_;  // Number of allocated buffers.
-  int timeout_count_;
-  VideoCaptureFormat capture_format_;
-  const int power_line_frequency_;
-
-  // Clockwise rotation in degrees.  This value should be 0, 90, 180, or 270.
-  int rotation_;
-
-  DISALLOW_IMPLICIT_CONSTRUCTORS(V4L2CaptureDelegate);
+// V4L2 color formats supported by V4L2CaptureDelegate derived classes.
+// This list is ordered by precedence of use -- but see caveats for MJPEG.
+static struct{
+  uint32_t fourcc;
+  VideoPixelFormat pixel_format;
+  size_t num_planes;
+} const kSupportedFormatsAndPlanarity[] = {
+  {V4L2_PIX_FMT_YUV420, PIXEL_FORMAT_I420, 1},
+  {V4L2_PIX_FMT_YUYV, PIXEL_FORMAT_YUY2, 1},
+  {V4L2_PIX_FMT_UYVY, PIXEL_FORMAT_UYVY, 1},
+#if !defined(OS_OPENBSD)
+  // TODO(mcasas): add V4L2_PIX_FMT_YVU420M when available in bots.
+  {V4L2_PIX_FMT_YUV420M, PIXEL_FORMAT_I420, 3},
+#endif
+  // MJPEG is usually sitting fairly low since we don't want to have to decode.
+  // However, is needed for large resolutions due to USB bandwidth limitations,
+  // so GetListOfUsableFourCcs() can duplicate it on top, see that method.
+  {V4L2_PIX_FMT_MJPEG, PIXEL_FORMAT_MJPEG, 1},
+  // JPEG works as MJPEG on some gspca webcams from field reports, see
+  // https://code.google.com/p/webrtc/issues/detail?id=529, put it as the least
+  // preferred format.
+  {V4L2_PIX_FMT_JPEG, PIXEL_FORMAT_MJPEG, 1},
 };
 
-// V4L2 color formats VideoCaptureDeviceLinux support.
-static const int32 kV4l2RawFmts[] = {
-  V4L2_PIX_FMT_YUV420,
-  V4L2_PIX_FMT_YUYV,
-  V4L2_PIX_FMT_UYVY
-};
-
-// USB VID and PID are both 4 bytes long.
-static const size_t kVidPidSize = 4;
-
-// /sys/class/video4linux/video{N}/device is a symlink to the corresponding
-// USB device info directory.
-static const char kVidPathTemplate[] =
-    "/sys/class/video4linux/%s/device/../idVendor";
-static const char kPidPathTemplate[] =
-    "/sys/class/video4linux/%s/device/../idProduct";
-
-static bool ReadIdFile(const std::string path, std::string* id) {
-  char id_buf[kVidPidSize];
-  FILE* file = fopen(path.c_str(), "rb");
-  if (!file)
-    return false;
-  const bool success = fread(id_buf, kVidPidSize, 1, file) == 1;
-  fclose(file);
-  if (!success)
-    return false;
-  id->append(id_buf, kVidPidSize);
-  return true;
+// static
+scoped_refptr<V4L2CaptureDelegate>
+V4L2CaptureDelegate::CreateV4L2CaptureDelegate(
+    const VideoCaptureDevice::Name& device_name,
+    const scoped_refptr<base::SingleThreadTaskRunner>& v4l2_task_runner,
+    int power_line_frequency) {
+  switch (device_name.capture_api_type()) {
+    case VideoCaptureDevice::Name::V4L2_SINGLE_PLANE:
+      return make_scoped_refptr(new V4L2CaptureDelegateSinglePlane(
+          device_name, v4l2_task_runner, power_line_frequency));
+    case VideoCaptureDevice::Name::V4L2_MULTI_PLANE:
+#if !defined(OS_OPENBSD)
+      return make_scoped_refptr(new V4L2CaptureDelegateMultiPlane(
+          device_name, v4l2_task_runner, power_line_frequency));
+    default:
+#endif
+      NOTIMPLEMENTED() << "Unknown V4L2 capture API type";
+      return scoped_refptr<V4L2CaptureDelegate>();
+  }
 }
 
-// This function translates Video4Linux pixel formats to Chromium pixel formats,
-// should only support those listed in GetListOfUsableFourCCs.
+//static
+size_t V4L2CaptureDelegate::GetNumPlanesForFourCc(uint32_t fourcc) {
+  for (const auto& fourcc_and_pixel_format : kSupportedFormatsAndPlanarity) {
+    if (fourcc_and_pixel_format.fourcc == fourcc)
+      return fourcc_and_pixel_format.num_planes;
+  }
+  DVLOG(1) << "Unknown fourcc " << FourccToString(fourcc);
+  return 0;
+}
+
 // static
-VideoPixelFormat VideoCaptureDeviceLinux::V4l2FourCcToChromiumPixelFormat(
-    uint32 v4l2_fourcc) {
-  const struct {
-    uint32 fourcc;
-    VideoPixelFormat pixel_format;
-  } kFourCcAndChromiumPixelFormat[] = {
-    {V4L2_PIX_FMT_YUV420, PIXEL_FORMAT_I420},
-    {V4L2_PIX_FMT_YUYV, PIXEL_FORMAT_YUY2},
-    {V4L2_PIX_FMT_UYVY, PIXEL_FORMAT_UYVY},
-    {V4L2_PIX_FMT_MJPEG, PIXEL_FORMAT_MJPEG},
-    {V4L2_PIX_FMT_JPEG, PIXEL_FORMAT_MJPEG},
-  };
-  for (const auto& fourcc_and_pixel_format : kFourCcAndChromiumPixelFormat) {
+VideoPixelFormat V4L2CaptureDelegate::V4l2FourCcToChromiumPixelFormat(
+    uint32_t v4l2_fourcc) {
+  for (const auto& fourcc_and_pixel_format : kSupportedFormatsAndPlanarity) {
     if (fourcc_and_pixel_format.fourcc == v4l2_fourcc)
       return fourcc_and_pixel_format.pixel_format;
   }
-  DVLOG(1) << "Unsupported pixel format: "
-           << GET_V4L2_FOURCC_CHAR(v4l2_fourcc, 0)
-           << GET_V4L2_FOURCC_CHAR(v4l2_fourcc, 1)
-           << GET_V4L2_FOURCC_CHAR(v4l2_fourcc, 2)
-           << GET_V4L2_FOURCC_CHAR(v4l2_fourcc, 3);
+  // Not finding a pixel format is OK during device capabilities enumeration.
+  // Let the caller decide if PIXEL_FORMAT_UNKNOWN is an error or not.
+  DVLOG(1) << "Unsupported pixel format: " << FourccToString(v4l2_fourcc);
   return PIXEL_FORMAT_UNKNOWN;
 }
 
 // static
-std::list<int> VideoCaptureDeviceLinux::GetListOfUsableFourCCs(
-    bool favour_mjpeg) {
-  std::list<int> fourccs;
-  for (size_t i = 0; i < arraysize(kV4l2RawFmts); ++i)
-    fourccs.push_back(kV4l2RawFmts[i]);
-  if (favour_mjpeg)
-    fourccs.push_front(V4L2_PIX_FMT_MJPEG);
-  else
-    fourccs.push_back(V4L2_PIX_FMT_MJPEG);
+std::list<uint32_t> V4L2CaptureDelegate::GetListOfUsableFourCcs(
+    bool prefer_mjpeg) {
+  std::list<uint32_t> supported_formats;
+  for (const auto& format : kSupportedFormatsAndPlanarity)
+    supported_formats.push_back(format.fourcc);
 
-  // JPEG works as MJPEG on some gspca webcams from field reports.
-  // Put it as the least preferred format.
-  fourccs.push_back(V4L2_PIX_FMT_JPEG);
-  return fourccs;
+  // Duplicate MJPEG on top of the list depending on |prefer_mjpeg|.
+  if (prefer_mjpeg)
+    supported_formats.push_front(V4L2_PIX_FMT_MJPEG);
+
+  return supported_formats;
 }
 
-const std::string VideoCaptureDevice::Name::GetModel() const {
-  // |unique_id| is of the form "/dev/video2".  |file_name| is "video2".
-  const std::string dev_dir = "/dev/";
-  DCHECK_EQ(0, unique_id_.compare(0, dev_dir.length(), dev_dir));
-  const std::string file_name =
-      unique_id_.substr(dev_dir.length(), unique_id_.length());
-
-  const std::string vidPath =
-      base::StringPrintf(kVidPathTemplate, file_name.c_str());
-  const std::string pidPath =
-      base::StringPrintf(kPidPathTemplate, file_name.c_str());
-
-  std::string usb_id;
-  if (!ReadIdFile(vidPath, &usb_id))
-    return "";
-  usb_id.append(":");
-  if (!ReadIdFile(pidPath, &usb_id))
-    return "";
-
-  return usb_id;
+//static
+std::string V4L2CaptureDelegate::FourccToString(uint32_t fourcc) {
+  return base::StringPrintf("%c%c%c%c", fourcc & 0xFF, (fourcc >> 8) & 0xFF,
+                            (fourcc >> 16) & 0xFF, (fourcc >> 24) & 0xFF);
 }
 
-VideoCaptureDeviceLinux::VideoCaptureDeviceLinux(const Name& device_name)
-    : v4l2_thread_("V4L2CaptureThread"),
-      device_name_(device_name) {
+V4L2CaptureDelegate::BufferTracker::BufferTracker() {
 }
 
-VideoCaptureDeviceLinux::~VideoCaptureDeviceLinux() {
-  // Check if the thread is running.
-  // This means that the device has not been StopAndDeAllocate()d properly.
-  DCHECK(!v4l2_thread_.IsRunning());
-  v4l2_thread_.Stop();
-}
-
-void VideoCaptureDeviceLinux::AllocateAndStart(
-    const VideoCaptureParams& params,
-    scoped_ptr<VideoCaptureDevice::Client> client) {
-  DCHECK(!capture_impl_);
-  if (v4l2_thread_.IsRunning())
-    return;  // Wrong state.
-  v4l2_thread_.Start();
-  capture_impl_ = new V4L2CaptureDelegate(device_name_,
-                                          v4l2_thread_.message_loop_proxy(),
-                                          GetPowerLineFrequencyForLocation());
-  v4l2_thread_.message_loop()->PostTask(
-      FROM_HERE,
-      base::Bind(
-          &VideoCaptureDeviceLinux::V4L2CaptureDelegate::AllocateAndStart,
-          capture_impl_,
-          params.requested_format.frame_size.width(),
-          params.requested_format.frame_size.height(),
-          params.requested_format.frame_rate,
-          base::Passed(&client)));
-}
-
-void VideoCaptureDeviceLinux::StopAndDeAllocate() {
-  if (!v4l2_thread_.IsRunning())
-    return;  // Wrong state.
-  v4l2_thread_.message_loop()->PostTask(
-      FROM_HERE,
-      base::Bind(
-          &VideoCaptureDeviceLinux::V4L2CaptureDelegate::StopAndDeAllocate,
-          capture_impl_));
-  v4l2_thread_.Stop();
-  // TODO(mcasas): VCDLinux called DeAllocateVideoBuffers() a second time after
-  // stopping |v4l2_thread_| to make sure buffers were completely deallocated.
-  // Investigate if that's needed, otherwise remove the following line and make
-  // V4L2CaptureDelegate::DeAllocateVideoBuffers() private.
-  capture_impl_->DeAllocateVideoBuffers();
-  capture_impl_ = NULL;
-}
-
-void VideoCaptureDeviceLinux::SetRotation(int rotation) {
-  if (v4l2_thread_.IsRunning()) {
-    v4l2_thread_.message_loop()->PostTask(
-        FROM_HERE,
-        base::Bind(
-            &VideoCaptureDeviceLinux::V4L2CaptureDelegate::SetRotation,
-            capture_impl_,
-            rotation));
+V4L2CaptureDelegate::BufferTracker::~BufferTracker() {
+  for (const auto& plane : planes_) {
+    if (plane.start == nullptr)
+      continue;
+    const int result = munmap(plane.start, plane.length);
+    PLOG_IF(ERROR, result < 0) << "Error munmap()ing V4L2 buffer";
   }
 }
 
-VideoCaptureDeviceLinux::V4L2CaptureDelegate::V4L2CaptureDelegate(
-        const Name& device_name,
-        const scoped_refptr<base::SingleThreadTaskRunner> v4l2_task_runner,
-        int power_line_frequency)
-    : v4l2_task_runner_(v4l2_task_runner),
+void V4L2CaptureDelegate::BufferTracker::AddMmapedPlane(uint8_t* const start,
+                                                        size_t length) {
+  Plane plane;
+  plane.start = start;
+  plane.length = length;
+  planes_.push_back(plane);
+}
+
+V4L2CaptureDelegate::V4L2CaptureDelegate(
+    const VideoCaptureDevice::Name& device_name,
+    const scoped_refptr<base::SingleThreadTaskRunner>& v4l2_task_runner,
+    int power_line_frequency)
+    : capture_type_((device_name.capture_api_type() ==
+                     VideoCaptureDevice::Name::V4L2_SINGLE_PLANE)
+                        ? V4L2_BUF_TYPE_VIDEO_CAPTURE
+                        : V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE),
+      v4l2_task_runner_(v4l2_task_runner),
+      device_name_(device_name),
+      power_line_frequency_(power_line_frequency),
       is_capturing_(false),
-      device_name_(device_name),
-      buffer_pool_(NULL),
-      buffer_pool_size_(0),
       timeout_count_(0),
-      power_line_frequency_(power_line_frequency),
       rotation_(0) {
 }
 
-VideoCaptureDeviceLinux::V4L2CaptureDelegate::~V4L2CaptureDelegate() {
-  DCHECK(!client_);
+V4L2CaptureDelegate::~V4L2CaptureDelegate() {
 }
 
-void VideoCaptureDeviceLinux::V4L2CaptureDelegate::AllocateAndStart(
+void V4L2CaptureDelegate::AllocateAndStart(
     int width,
     int height,
     float frame_rate,
-    scoped_ptr<Client> client) {
+    scoped_ptr<VideoCaptureDevice::Client> client) {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
   DCHECK(client);
   client_ = client.Pass();
 
   // Need to open camera with O_RDWR after Linux kernel 3.3.
   device_fd_.reset(HANDLE_EINTR(open(device_name_.id().c_str(), O_RDWR)));
   if (!device_fd_.is_valid()) {
     SetErrorState("Failed to open V4L2 device driver file.");
     return;
   }
 
   v4l2_capability cap = {};
   if (!((HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QUERYCAP, &cap)) == 0) &&
-      (cap.capabilities & V4L2_CAP_VIDEO_CAPTURE &&
-      !(cap.capabilities & V4L2_CAP_VIDEO_OUTPUT)))) {
+        ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE ||
+          cap.capabilities & V4L2_CAP_VIDEO_CAPTURE_MPLANE) &&
+         !(cap.capabilities & V4L2_CAP_VIDEO_OUTPUT) &&
+         !(cap.capabilities & V4L2_CAP_VIDEO_OUTPUT_MPLANE)))) {
     device_fd_.reset();
     SetErrorState("This is not a V4L2 video capture device");
     return;
   }
 
   // Get supported video formats in preferred order.
   // For large resolutions, favour mjpeg over raw formats.
-  const std::list<int>& desired_v4l2_formats =
-      GetListOfUsableFourCCs(width > kMjpegWidth || height > kMjpegHeight);
-  std::list<int>::const_iterator best = desired_v4l2_formats.end();
+  const std::list<uint32_t>& desired_v4l2_formats =
+      GetListOfUsableFourCcs(width > kMjpegWidth || height > kMjpegHeight);
+  std::list<uint32_t>::const_iterator best = desired_v4l2_formats.end();
 
   v4l2_fmtdesc fmtdesc = {};
-  fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+  fmtdesc.type = capture_type_;
   for (; HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_ENUM_FMT, &fmtdesc)) == 0;
        ++fmtdesc.index) {
     best = std::find(desired_v4l2_formats.begin(), best, fmtdesc.pixelformat);
   }
   if (best == desired_v4l2_formats.end()) {
     SetErrorState("Failed to find a supported camera format.");
     return;
   }
 
-  v4l2_format video_fmt = {};
-  video_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-  video_fmt.fmt.pix.sizeimage = 0;
-  video_fmt.fmt.pix.width = width;
-  video_fmt.fmt.pix.height = height;
-  video_fmt.fmt.pix.pixelformat = *best;
-  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_S_FMT, &video_fmt)) < 0) {
+  DVLOG(1) << "Chosen pixel format is " << FourccToString(*best);
+
+  video_fmt_.type = capture_type_;
+  if (!FillV4L2Format(&video_fmt_, width, height, *best)) {
+    SetErrorState("Failed filling in V4L2 Format");
+    return;
+  }
+
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_S_FMT, &video_fmt_)) < 0) {
     SetErrorState("Failed to set video capture format");
     return;
   }
+  const VideoPixelFormat pixel_format =
+      V4l2FourCcToChromiumPixelFormat(video_fmt_.fmt.pix.pixelformat);
+  if (pixel_format == PIXEL_FORMAT_UNKNOWN) {
+    SetErrorState("Unsupported pixel format");
+    return;
+  }
 
   // Set capture framerate in the form of capture interval.
   v4l2_streamparm streamparm = {};
-  streamparm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+  streamparm.type = capture_type_;
   // The following line checks that the driver knows about framerate get/set.
   if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_G_PARM, &streamparm)) >= 0) {
     // Now check if the device is able to accept a capture framerate set.
     if (streamparm.parm.capture.capability & V4L2_CAP_TIMEPERFRAME) {
       // |frame_rate| is float, approximate by a fraction.
       streamparm.parm.capture.timeperframe.numerator =
           media::kFrameRatePrecision;
-      streamparm.parm.capture.timeperframe.denominator = (frame_rate) ?
-          (frame_rate * media::kFrameRatePrecision) :
-          (kTypicalFramerate * media::kFrameRatePrecision);
+      streamparm.parm.capture.timeperframe.denominator =
+          (frame_rate) ? (frame_rate * media::kFrameRatePrecision)
+                       : (kTypicalFramerate * media::kFrameRatePrecision);
 
       if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_S_PARM, &streamparm)) <
           0) {
         SetErrorState("Failed to set camera framerate");
         return;
       }
       DVLOG(2) << "Actual camera driverframerate: "
                << streamparm.parm.capture.timeperframe.denominator << "/"
                << streamparm.parm.capture.timeperframe.numerator;
     }
   }
   // TODO(mcasas): what should be done if the camera driver does not allow
   // framerate configuration, or the actual one is different from the desired?
 
   // Set anti-banding/anti-flicker to 50/60Hz. May fail due to not supported
   // operation (|errno| == EINVAL in this case) or plain failure.
-  if ((power_line_frequency_ == kPowerLine50Hz) ||
-      (power_line_frequency_ == kPowerLine60Hz)) {
+  if ((power_line_frequency_ == V4L2_CID_POWER_LINE_FREQUENCY_50HZ) ||
+      (power_line_frequency_ == V4L2_CID_POWER_LINE_FREQUENCY_60HZ) ||
+      (power_line_frequency_ == V4L2_CID_POWER_LINE_FREQUENCY_AUTO)) {
     struct v4l2_control control = {};
     control.id = V4L2_CID_POWER_LINE_FREQUENCY;
-    control.value = (power_line_frequency_ == kPowerLine50Hz)
-                        ? V4L2_CID_POWER_LINE_FREQUENCY_50HZ
-                        : V4L2_CID_POWER_LINE_FREQUENCY_60HZ;
-    HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_S_CTRL, &control));
+    control.value = power_line_frequency_;
+    const int retval =
+        HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_S_CTRL, &control));
+    if (retval != 0)
+      DVLOG(1) << "Error setting power line frequency removal";
   }
 
-  capture_format_.frame_size.SetSize(video_fmt.fmt.pix.width,
-                                     video_fmt.fmt.pix.height);
+  capture_format_.frame_size.SetSize(video_fmt_.fmt.pix.width,
+                                     video_fmt_.fmt.pix.height);
   capture_format_.frame_rate = frame_rate;
-  capture_format_.pixel_format =
-      V4l2FourCcToChromiumPixelFormat(video_fmt.fmt.pix.pixelformat);
+  capture_format_.pixel_format = pixel_format;
 
-  if (!AllocateVideoBuffers()) {
-    SetErrorState("Allocate buffer failed (Cannot recover from this error)");
+  v4l2_requestbuffers r_buffer = {};
+  r_buffer.type = capture_type_;
+  r_buffer.memory = V4L2_MEMORY_MMAP;
+  r_buffer.count = kNumVideoBuffers;
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_REQBUFS, &r_buffer)) < 0) {
+    SetErrorState("Error requesting MMAP buffers from V4L2");
     return;
   }
+  for (unsigned int i = 0; i < r_buffer.count; ++i) {
+    if (!MapAndQueueBuffer(i)) {
+      SetErrorState("Allocate buffer failed");
+      return;
+    }
+  }
 
-  const v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_STREAMON, &type)) < 0) {
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_STREAMON, &capture_type_))
+      < 0) {
     SetErrorState("VIDIOC_STREAMON failed");
     return;
   }
 
   is_capturing_ = true;
   // Post task to start fetching frames from v4l2.
   v4l2_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&VideoCaptureDeviceLinux::V4L2CaptureDelegate::DoCapture,
-                 this));
+      FROM_HERE, base::Bind(&V4L2CaptureDelegate::DoCapture, this));
 }
 
-void VideoCaptureDeviceLinux::V4L2CaptureDelegate::StopAndDeAllocate() {
+void V4L2CaptureDelegate::StopAndDeAllocate() {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
-
-  const v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_STREAMOFF, &type)) < 0) {
+  // The order is important: stop streaming, clear |buffer_pool_|,
+  // thus munmap()ing the v4l2_buffers, and then return them to the OS.
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_STREAMOFF, &capture_type_))
+      < 0) {
     SetErrorState("VIDIOC_STREAMOFF failed");
     return;
   }
-  // We don't dare to deallocate the buffers if we can't stop the capture
-  // device.
-  if (!DeAllocateVideoBuffers())
-    SetErrorState("Failed to reset buffers");
 
-  // We need to close and open the device if we want to change the settings.
-  // Otherwise VIDIOC_S_FMT will return error. Sad but true.
+  buffer_tracker_pool_.clear();
+
+  v4l2_requestbuffers r_buffer = {};
+  r_buffer.type = capture_type_;
+  r_buffer.memory = V4L2_MEMORY_MMAP;
+  r_buffer.count = 0;
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_REQBUFS, &r_buffer)) < 0)
+    SetErrorState("Failed to VIDIOC_REQBUFS with count = 0");
+
+  // At this point we can close the device.
+  // This is also needed for correctly changing settings later via VIDIOC_S_FMT.
   device_fd_.reset();
   is_capturing_ = false;
   client_.reset();
 }
 
-void VideoCaptureDeviceLinux::V4L2CaptureDelegate::SetRotation(int rotation) {
+void V4L2CaptureDelegate::SetRotation(int rotation) {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
   DCHECK(rotation >= 0 && rotation < 360 && rotation % 90 == 0);
   rotation_ = rotation;
 }
 
-void VideoCaptureDeviceLinux::V4L2CaptureDelegate::DoCapture() {
+bool V4L2CaptureDelegate::MapAndQueueBuffer(int index) {
+  v4l2_buffer buffer;
+  FillV4L2Buffer(&buffer, index);
+
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QUERYBUF, &buffer)) < 0) {
+    DLOG(ERROR) << "Error querying status of a MMAP V4L2 buffer";
+    return false;
+  }
+
+  const scoped_refptr<BufferTracker>& buffer_tracker = CreateBufferTracker();
+  if (!buffer_tracker->Init(device_fd_.get(), buffer)) {
+    DLOG(ERROR) << "Error creating BufferTracker";
+    return false;
+  }
+  buffer_tracker_pool_.push_back(buffer_tracker);
+
+  // Enqueue the buffer in the drivers incoming queue.
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QBUF, &buffer)) < 0) {
+    DLOG(ERROR) << "Error enqueuing a V4L2 buffer back into the driver";
+    return false;
+  }
+  return true;
+}
+
+void V4L2CaptureDelegate::FillV4L2Buffer(v4l2_buffer* buffer,
+                                         int i) const {
+  memset(buffer, 0, sizeof(*buffer));
+  buffer->memory = V4L2_MEMORY_MMAP;
+  buffer->index = i;
+  FinishFillingV4L2Buffer(buffer);
+}
+
+void V4L2CaptureDelegate::DoCapture() {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
   if (!is_capturing_)
     return;
 
   pollfd device_pfd = {};
   device_pfd.fd = device_fd_.get();
   device_pfd.events = POLLIN;
   const int result = HANDLE_EINTR(poll(&device_pfd, 1, kCaptureTimeoutMs));
   if (result < 0) {
     SetErrorState("Poll failed");
     return;
   }
   // Check if poll() timed out; track the amount of times it did in a row and
   // throw an error if it times out too many times.
   if (result == 0) {
     timeout_count_++;
     if (timeout_count_ >= kContinuousTimeoutLimit) {
       SetErrorState("Multiple continuous timeouts while read-polling.");
       timeout_count_ = 0;
       return;
     }
   } else {
     timeout_count_ = 0;
   }
 
-  // Check if the driver has filled a buffer.
+  // Deenqueue, send and reenqueue a buffer if the driver has filled one in.
   if (device_pfd.revents & POLLIN) {
-    v4l2_buffer buffer = {};
-     buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-     buffer.memory = V4L2_MEMORY_MMAP;
+    v4l2_buffer buffer;
+    FillV4L2Buffer(&buffer, 0);
+
     if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_DQBUF, &buffer)) < 0) {
       SetErrorState("Failed to dequeue capture buffer");
       return;
     }
-    client_->OnIncomingCapturedData(
-        static_cast<uint8*>(buffer_pool_[buffer.index].start),
-        buffer.bytesused,
-        capture_format_,
-        rotation_,
-        base::TimeTicks::Now());
 
-    if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QBUF, &buffer)) < 0)
+    SendBuffer(buffer_tracker_pool_[buffer.index], video_fmt_);
+
+    if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QBUF, &buffer)) < 0) {
       SetErrorState("Failed to enqueue capture buffer");
+      return;
+    }
   }
 
   v4l2_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&VideoCaptureDeviceLinux::V4L2CaptureDelegate::DoCapture,
-                 this));
+      FROM_HERE, base::Bind(&V4L2CaptureDelegate::DoCapture, this));
 }
 
-bool VideoCaptureDeviceLinux::V4L2CaptureDelegate::AllocateVideoBuffers() {
-  v4l2_requestbuffers r_buffer = {};
-  r_buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-  r_buffer.memory = V4L2_MEMORY_MMAP;
-  r_buffer.count = kNumVideoBuffers;
-  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_REQBUFS, &r_buffer)) < 0) {
-    DLOG(ERROR) << "Error requesting MMAP buffers from V4L2";
-    return false;
-  }
-  buffer_pool_size_ = r_buffer.count;
-  buffer_pool_ = new Buffer[buffer_pool_size_];
-  for (unsigned int i = 0; i < r_buffer.count; ++i) {
-    v4l2_buffer buffer = {};
-    buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-    buffer.memory = V4L2_MEMORY_MMAP;
-    buffer.index = i;
-    buffer.length = 1;
-    if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QUERYBUF, &buffer)) < 0) {
-      DLOG(ERROR) << "Error querying status of a MMAP V4L2 buffer";
-      return false;
-    }
-
-    // Some devices require mmap() to be called with both READ and WRITE.
-    // See http://crbug.com/178582.
-    buffer_pool_[i].start = mmap(NULL, buffer.length, PROT_READ | PROT_WRITE,
-        MAP_SHARED, device_fd_.get(), buffer.m.offset);
-    if (buffer_pool_[i].start == MAP_FAILED) {
-      DLOG(ERROR) << "Error mmmap()ing a V4L2 buffer into userspace";
-      return false;
-    }
-
-    buffer_pool_[i].length = buffer.length;
-    // Enqueue the buffer in the drivers incoming queue.
-    if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QBUF, &buffer)) < 0) {
-      DLOG(ERROR)
-          << "Error enqueuing a V4L2 buffer back to the drivers incoming queue";
-      return false;
-    }
-  }
-  return true;
-}
-
-bool VideoCaptureDeviceLinux::V4L2CaptureDelegate::DeAllocateVideoBuffers() {
-  if (!buffer_pool_)
-    return true;
-
-  for (int i = 0; i < buffer_pool_size_; ++i)
-    munmap(buffer_pool_[i].start, buffer_pool_[i].length);
-
-  v4l2_requestbuffers r_buffer = {};
-  r_buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-  r_buffer.memory = V4L2_MEMORY_MMAP;
-  r_buffer.count = 0;
-  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_REQBUFS, &r_buffer)) < 0)
-    return false;
-
-  delete [] buffer_pool_;
-  buffer_pool_ = NULL;
-  buffer_pool_size_ = 0;
-  return true;
-}
-
-void VideoCaptureDeviceLinux::V4L2CaptureDelegate::SetErrorState(
-    const std::string& reason) {
+void V4L2CaptureDelegate::SetErrorState(const std::string& reason) {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
   is_capturing_ = false;
   client_->OnError(reason);
 }
 
 }  // namespace media