Add new virtio-media V4l2 stream proxy virtual device

base/cvd/cuttlefish/host/commands/run_cvd/launch/vhost_user_media_devices.cpp

@@ -17,6 +17,7 @@
 
 #include <fcntl.h>
 
+#include <optional>
 #include <string>
 #include <unordered_set>
 #include <utility>
@@ -67,23 +68,44 @@ class VhostUserMediaDevices : public CommandSource {
     for (int index = 0; index < instance_.media_configs().size(); index++) {
       auto config = instance_.media_configs()[index];
       std::string binary_path;
+      std::optional<Command> cmd;
       if (config.type ==
           CuttlefishConfig::MediaType::kV4l2EmulatedCameraMPlane) {
         binary_path = VhostUserMediaEmulatedCameraMPlaneBinary();
+        cmd.emplace(NewCommand(binary_path, instance_.media_socket_path(index),
+                               config.lens_facing));
       } else if (config.type ==
                  CuttlefishConfig::MediaType::kV4l2EmulatedCameraSPlane) {
         binary_path = VhostUserMediaEmulatedCameraSPlaneBinary();
+        cmd.emplace(NewCommand(binary_path, instance_.media_socket_path(index),
+                               config.lens_facing));
+      } else if (config.type == CuttlefishConfig::MediaType::kV4l2StreamProxy) {
+        CF_EXPECT(config.v4l2_stream_proxy.has_value(),
+                  "Missing v4l2_stream_proxy config");
+        binary_path = VhostUserMediaV4l2StreamProxyBinary();
+        cmd.emplace(
+            NewCommand(binary_path, instance_.media_socket_path(index), ""));
+        cmd->AddParameter("--input_path=",
+                          config.v4l2_stream_proxy->input_path);
+        cmd->AddParameter(
+            "--input_width=",
+            std::to_string(config.v4l2_stream_proxy->input_width));
+        cmd->AddParameter(
+            "--input_height=",
+            std::to_string(config.v4l2_stream_proxy->input_height));
+        cmd->AddParameter("--input_fps=", config.v4l2_stream_proxy->input_fps);
       } else if (config.type == CuttlefishConfig::MediaType::kV4l2Proxy) {
         continue;
       } else {
         CF_EXPECT(false, "unknown media type");
       }
-      Command cmd = NewCommand(binary_path, instance_.media_socket_path(index),
-                               config.lens_facing);
+
+      CF_EXPECT(cmd.has_value(), "Command was not initialized");
+
       Command cmd_log_tee = CF_EXPECT(
-          log_tee_.CreateLogTee(cmd, "vhu_media_simple_device", kStdErr),
+          log_tee_.CreateLogTee(*cmd, "vhu_media_simple_device", kStdErr),
           "Failed to create log tee command for media device");
-      commands.emplace_back(std::move(cmd));
+      commands.emplace_back(std::move(*cmd));
       commands.emplace_back(std::move(cmd_log_tee));
     }
     return commands;

base/cvd/cuttlefish/host/commands/vhost_user_media/Cargo.toml

@@ -3,6 +3,7 @@ members = [
     "emulated_camera_mplane",
     "emulated_camera_splane",
     "vhu_media",
+    "v4l2_stream_proxy",
 ]
 
 [workspace.dependencies]
@@ -11,6 +12,7 @@ env_logger = "0.11"
 image = "0.24"
 libc = "0.2"
 log = "0.4"
+nix = "0.29.0"
 thiserror = "2.0"
 v4l2r = { version = "0.0.6", features = ["arch64"] }
 vhost = { version = "0.16.0", features = ["vhost-user-backend"] }

base/cvd/cuttlefish/host/commands/vhost_user_media/v4l2_stream_proxy/BUILD.bazel

@@ -0,0 +1,47 @@
+load("@rules_rust//rust:defs.bzl", "rust_binary")
+load("@vhost_user_media_workspace_crates//:defs.bzl", "crate_deps")
+
+package(default_visibility = ["//:android_cuttlefish"])
+
+alias(
+    name = "v4l2_stream_proxy",
+    actual = select({
+        "@platforms//cpu:x86_64": ":v4l2_stream_proxy_binary",
+        "//conditions:default": ":unsupported_binary",
+    }),
+)
+
+rust_binary(
+    name = "v4l2_stream_proxy_binary",
+    srcs = [
+        "src/device.rs",
+        "src/main.rs",
+        "src/worker.rs",
+    ],
+    edition = "2024",
+    deps = crate_deps([
+        "clap",
+        "env_logger",
+        "libc",
+        "log",
+        "nix",
+        "v4l2r",
+        "vhost-user-backend",
+        "virtio-media",
+        "virtio-queue",
+        "vm-memory",
+    ]) + [
+        "//cuttlefish/host/commands/vhost_user_media/vhu_media",
+    ],
+)
+
+genrule(
+    name = "unsupported_binary",
+    outs = ["unsupported.sh"],
+    cmd = """cat << 'EOF' > $@
+#!/bin/bash
+echo "platform unsupported" >&2
+exit 1
+EOF""",
+    executable = True,
+)

base/cvd/cuttlefish/host/commands/vhost_user_media/v4l2_stream_proxy/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "v4l2_stream_proxy"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+clap = { workspace = true }
+env_logger = { workspace = true }
+libc = { workspace = true }
+log = { workspace = true }
+nix = { workspace = true, features = ["event", "poll"] }
+v4l2r = { workspace = true }
+vhost-user-backend = { workspace = true }
+vhu_media = { workspace = true }
+virtio-media = { workspace = true }
+virtio-queue = { workspace = true }
+vm-memory = { workspace = true }

base/cvd/cuttlefish/host/commands/vhost_user_media/v4l2_stream_proxy/README.md

@@ -0,0 +1,70 @@
+# V4L2 Stream Proxy Host Tool
+
+This directory contains the `v4l2_stream_proxy` vhost-user device. To test this device, you can use the provided helper script to start a video stream on the host, which can then be proxied by the `cvd` tool from the host to the guest.
+
+The test helper script is located at:
+`tools/testutils/ffmpeg_v4l2_stream_proxy.sh` (relative to the repository root).
+
+## Prerequisites
+
+The script requires `ffmpeg` (and `ffprobe` if streaming from a file) to be installed on the host system.
+
+```bash
+sudo apt install ffmpeg
+```
+
+## Usage
+
+The script creates a FIFO (named pipe) and runs `ffmpeg` in a loop to continuously feed video into it. When `ffmpeg` exits (or fails), the script automatically restarts it. `ffmpeg`'s normal behavior includes exiting when the FIFO's reader closes the FIFO. This happens whenever the camera's stream is stopped in the guest.
+
+In both modes (Test Source and Video File), the script will print an argument to add to `cvd create`/`cvd start` that will provide a video device in the guest that matches the host configuration.
+
+### 1. Test Source Mode (Default)
+
+If no video file is provided, the script uses `ffmpeg`'s `testsrc` filter to generate a synthetic test pattern (color bars and a timer).
+
+To start streaming a 640x480 video at 30 fps (defaults):
+
+```bash
+tools/testutils/ffmpeg_v4l2_stream_proxy.sh
+```
+
+You can customize the resolution and frame rate:
+
+```bash
+tools/testutils/ffmpeg_v4l2_stream_proxy.sh -w 1280 -H 720 -r 60
+```
+
+Available options:
+*   `-w <width>`: Video width (default: 640)
+*   `-H <height>`: Video height (default: 480)
+*   `-r <fps>`: Video FPS (default: 30)
+*   `-p <fifo_path>`: Path to the FIFO to create/use (default: `/tmp/v4l2_fifo`)
+
+### 2. Video File Mode
+
+To stream a video file (e.g., `.mp4`, `.mjpeg`, `.h264`) in a loop:
+
+```bash
+tools/testutils/ffmpeg_v4l2_stream_proxy.sh -f /path/to/video.mp4
+```
+
+In this mode, the script uses `ffprobe` to automatically detect the video's resolution and frame rate.
+
+Available options:
+*   `-f <video_file>`: Path to the host video file
+*   `-p <fifo_path>`: Path to the FIFO to create/use (default: `/tmp/v4l2_fifo`)
+
+## Connecting to Cuttlefish (CVD)
+
+Once the streaming script is running, start Cuttlefish and configure it to use the stream. Use the parameters printed by the script (or the defaults) to configure the `--media` flag.
+
+Example CVD launch command:
+
+```bash
+cvd create --media=v4l2_stream_proxy:input_path=/tmp/v4l2_fifo:input_width=640:input_height=480:input_fps=30
+```
+
+## Stopping the Stream
+
+Press `Ctrl+C` in the terminal running the script. The script will catch the interrupt, kill the active `ffmpeg` process, and clean up the FIFO if it was created by the script.