16 bpp video stream capture, render and createImageBitmap(video) using (CPU) shared memory buffers

media/capture/video/linux/v4l2_capture_delegate.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 "media/capture/video/linux/v4l2_capture_delegate.h"
 
 #include <poll.h>
 #include <sys/fcntl.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/files/file_enumerator.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/strings/stringprintf.h"
 #include "build/build_config.h"
 #include "media/base/bind_to_current_loop.h"
 #include "media/capture/video/blob_utils.h"
 #include "media/capture/video/linux/video_capture_device_linux.h"
 
+// TODO(astojilj): Remove V4L2_PIX_FMT_Z16/INVZ when videodev2.h gets updated.
+#ifndef V4L2_PIX_FMT_Z16

[mcasas, 2016/10/24 19:48:47]

These two identifiers were introduced in 
kernel 4.6 [1], so please sandwich it all
like:

#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 6,0)
// 16 bit depth, Realsense F200.
#define V4L2_PIX_FMT_Z16 v4l2_fourcc('Z', '1', '6', ' ')
// 16 bit depth, Realsense SR300.
#define V4L2_PIX_FMT_INVZ v4l2_fourcc('I', 'N', 'V', 'Z')
#endif


[1] http://lxr.free-electrons.com/ident?v=4.6;i=V4L2_PIX_FMT_Z16

[aleksandar.stojiljkovic, 2016/10/25 10:12:28]

Done. Thanks.

+// 16 bit depth, Realsense F200.
+#define V4L2_PIX_FMT_Z16 v4l2_fourcc('Z', '1', '6', ' ')
+#endif
+#ifndef V4L2_PIX_FMT_INVZ
+// 16 bit depth, Realsense SR300.
+#define V4L2_PIX_FMT_INVZ v4l2_fourcc('I', 'N', 'V', 'Z')
+#endif
+
 namespace media {
 
 // 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_t kNumVideoBuffers = 4;
 // Timeout in milliseconds v4l2_thread_ blocks waiting for a frame from the hw.
 // This value has been fine tuned. Before changing or modifying it see
 // https://crbug.com/470717
@@ skipping 11 matching lines @@
 const int kZoomMultiplier = 100;
 
 // 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_Y16, PIXEL_FORMAT_Y16, 1},
+    {V4L2_PIX_FMT_Z16, PIXEL_FORMAT_Y16, 1},
+    {V4L2_PIX_FMT_INVZ, PIXEL_FORMAT_Y16, 1},
     {V4L2_PIX_FMT_YUYV, PIXEL_FORMAT_YUY2, 1},
     {V4L2_PIX_FMT_UYVY, PIXEL_FORMAT_UYVY, 1},
     {V4L2_PIX_FMT_RGB24, PIXEL_FORMAT_RGB24, 1},
     // MJPEG is usually sitting fairly low since we don't want to have to
     // decode. However, it 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
@@ skipping 497 matching lines @@
       return;
     }
 
     buffer_tracker_pool_[buffer.index]->set_payload_size(buffer.bytesused);
     const scoped_refptr<BufferTracker>& buffer_tracker =
         buffer_tracker_pool_[buffer.index];
 
     base::TimeDelta timestamp =
         base::TimeDelta::FromSeconds(buffer.timestamp.tv_sec) +
         base::TimeDelta::FromMicroseconds(buffer.timestamp.tv_usec);
-    client_->OnIncomingCapturedData(
-        buffer_tracker->start(), buffer_tracker->payload_size(),
-        capture_format_, rotation_, base::TimeTicks::Now(), timestamp);
+#ifdef V4L2_BUF_FLAG_ERROR
+    if (buffer.flags & V4L2_BUF_FLAG_ERROR) {
+      LOG(ERROR) << "Dequeued v4l2 buffer contains corrupted data ("
+                 << buffer.bytesused << " bytes).";
+      buffer.bytesused = 0;
+    } else
+#endif
+      client_->OnIncomingCapturedData(
+          buffer_tracker->start(), buffer_tracker->payload_size(),
+          capture_format_, rotation_, base::TimeTicks::Now(), timestamp);
 
     while (!take_photo_callbacks_.empty()) {
       VideoCaptureDevice::TakePhotoCallback cb =
           std::move(take_photo_callbacks_.front());
       take_photo_callbacks_.pop();
 
       mojom::BlobPtr blob =
           Blobify(buffer_tracker->start(), buffer.bytesused, capture_format_);
       if (blob)
         cb.Run(std::move(blob));
@@ skipping 36 matching lines @@
     DLOG(ERROR) << "Error mmap()ing a V4L2 buffer into userspace";
     return false;
   }
   start_ = static_cast<uint8_t*>(start);
   length_ = buffer.length;
   payload_size_ = 0;
   return true;
 }
 
 }  // namespace media