+#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;
+ }
+}