Add support for V4L2 output.

[nageru] / nageru / v4l_output.cpp

diff --git a/nageru/v4l_output.cpp b/nageru/v4l_output.cpp
new file mode 100644 (file)
index 0000000..f6c4e85
--- /dev/null
+++ b/nageru/v4l_output.cpp
@@ -0,0 +1,77 @@
+#include "v4l_output.h"
+
+#include <assert.h>
+#include <fcntl.h>
+#include <linux/videodev2.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+#include "shared/memcpy_interleaved.h"
+
+V4LOutput::V4LOutput(const char *device_path, unsigned width, unsigned height)
+       : width(width), height(height),
+         image_size_bytes(width * height + (width / 2) * (height / 2) * 2),
+         yuv420_buf(new uint8_t[image_size_bytes])
+{
+       video_fd = open(device_path, O_WRONLY);
+       if (video_fd == -1) {
+               perror(device_path);
+               exit(1);
+       }
+
+       v4l2_format fmt;
+       memset(&fmt, 0, sizeof(fmt));
+       fmt.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+       fmt.fmt.pix.width = width;
+       fmt.fmt.pix.height = width;
+       fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420;
+       fmt.fmt.pix.field = V4L2_FIELD_NONE;
+       fmt.fmt.pix.bytesperline = 0;
+       fmt.fmt.pix.sizeimage = image_size_bytes;
+       fmt.fmt.pix.colorspace = V4L2_COLORSPACE_SRGB;
+       int err = ioctl(video_fd, VIDIOC_S_FMT, &fmt);
+       if (err == -1) {
+               perror("ioctl(VIDIOC_S_FMT)");
+               exit(1);
+       }
+}
+
+V4LOutput::~V4LOutput()
+{
+       close(video_fd);
+}
+
+void V4LOutput::send_frame(const uint8_t *data)
+{
+       // Seemingly NV12 isn't a very common format among V4L2 consumers,
+       // so we convert from our usual NV12 to YUV420. We get an unneeded
+       // memcpy() of the luma data, but hopefully, we'll manage.
+       const size_t luma_size = width * height;
+       const size_t chroma_size = (width / 2) * (height / 2);
+       memcpy(yuv420_buf.get(), data, luma_size);
+       memcpy_interleaved(
+               yuv420_buf.get() + luma_size,
+               yuv420_buf.get() + luma_size + chroma_size,
+               data + luma_size, 2 * chroma_size);
+
+       const uint8_t *ptr = yuv420_buf.get();
+       size_t bytes_left = image_size_bytes;
+       while (bytes_left > 0) {
+               int err = write(video_fd, ptr, bytes_left);
+               if (err == -1) {
+                       perror("V4L write");
+                       exit(1);
+               }
+               if (err == 0) {
+                       fprintf(stderr, "WARNING: Short V4L write() (only wrote %zu of %zu bytes), skipping rest of frame.\n",
+                               image_size_bytes - bytes_left, image_size_bytes);
+                       return;
+               }
+               assert(err > 0);
+               bytes_left -= err;
+               ptr += err;
+       }
+}