Support for v4l2loopback

app/meson.build

@@ -21,12 +21,15 @@ src = [
     'src/stream.c',
     'src/tiny_xpm.c',
     'src/video_buffer.c',
+    'src/v4l2sink.c',
     'src/util/net.c',
     'src/util/process.c',
     'src/util/str_util.c',
     'src/util/thread.c',
 ]
 
+conf = configuration_data()
+
 if host_machine.system() == 'windows'
     src += [ 'src/sys/win/process.c' ]
 else
@@ -49,6 +52,11 @@ if not get_option('crossbuild_windows')
         dependency('sdl2'),
     ]
 
+    if host_machine.system() == 'linux'
+        dependencies += dependency('libavdevice')
+        conf.set('V4L2SINK', '1')
+    endif
+
 else
 
     # cross-compile mingw32 build (from Linux to Windows)
@@ -90,8 +98,6 @@ if host_machine.system() == 'windows'
     dependencies += cc.find_library('ws2_32')
 endif
 
-conf = configuration_data()
-
 foreach f : check_functions
   if cc.has_function(f)
     define = 'HAVE_' + f.underscorify().to_upper()

app/src/cli.c

@@ -179,6 +179,11 @@ scrcpy_print_usage(const char *arg0) {
         "        on exit.\n"
         "        It only shows physical touches (not clicks from scrcpy).\n"
         "\n"
+#ifdef V4L2SINK
+        "    --v4l2sink /dev/videoN\n"
+        "        Output to v4l2loopback device. It will lock video orientation. Use --lock-video-orientation to override the rotation.\n"
+        "\n"
+#endif
         "    -v, --version\n"
         "        Print the version of scrcpy.\n"
         "\n"
@@ -667,6 +672,7 @@ guess_record_format(const char *filename) {
 #define OPT_LEGACY_PASTE           1024
 #define OPT_ENCODER_NAME           1025
 #define OPT_POWER_OFF_ON_CLOSE     1026
+#define OPT_V4L2SINK               1027
 
 bool
 scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
@@ -708,6 +714,9 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
         {"show-touches",           no_argument,       NULL, 't'},
         {"stay-awake",             no_argument,       NULL, 'w'},
         {"turn-screen-off",        no_argument,       NULL, 'S'},
+#ifdef V4L2SINK
+        {"v4l2sink",               required_argument, NULL, OPT_V4L2SINK},
+#endif
         {"verbosity",              required_argument, NULL, 'V'},
         {"version",                no_argument,       NULL, 'v'},
         {"window-title",           required_argument, NULL, OPT_WINDOW_TITLE},
@@ -890,14 +899,28 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
             case OPT_POWER_OFF_ON_CLOSE:
                 opts->power_off_on_close = true;
                 break;
+#ifdef V4L2SINK
+            case OPT_V4L2SINK:
+                opts->v4l2sink_device = optarg;
+                break;
+#endif
             default:
                 // getopt prints the error message on stderr
                 return false;
         }
     }
 
-    if (!opts->display && !opts->record_filename) {
+    //v4l2loopback can't handle resolution changes so we must lock video orientation in case this is used
+    if (opts->v4l2sink_device && opts->lock_video_orientation < 0) {
+        opts->lock_video_orientation = 0;
+    }
+
+    if (!opts->display && !opts->record_filename && !opts->v4l2sink_device) {
+#ifdef V4L2SINK
+        LOGE("-N/--no-display requires screen recording (-r/--record) or sink to v4l2loopback device (--v4l2sink)");
+#else
         LOGE("-N/--no-display requires screen recording (-r/--record)");
+#endif
         return false;
     }
 

app/src/main.c

@@ -6,6 +6,9 @@
 #include <stdbool.h>
 #include <unistd.h>
 #include <libavformat/avformat.h>
+#ifdef V4L2SINK
+#include <libavdevice/avdevice.h>
+#endif
 #define SDL_MAIN_HANDLED // avoid link error on Linux Windows Subsystem
 #include <SDL2/SDL.h>
 
@@ -28,6 +31,11 @@ print_version(void) {
     fprintf(stderr, " - libavutil %d.%d.%d\n", LIBAVUTIL_VERSION_MAJOR,
                                                LIBAVUTIL_VERSION_MINOR,
                                                LIBAVUTIL_VERSION_MICRO);
+#ifdef V4L2SINK
+    fprintf(stderr, " - libavdevice %d.%d.%d\n", LIBAVDEVICE_VERSION_MAJOR,
+                                                 LIBAVDEVICE_VERSION_MINOR,
+                                                 LIBAVDEVICE_VERSION_MICRO);
+#endif
 }
 
 static SDL_LogPriority
@@ -89,6 +97,9 @@ main(int argc, char *argv[]) {
 #ifdef SCRCPY_LAVF_REQUIRES_REGISTER_ALL
     av_register_all();
 #endif
+#ifdef V4L2SINK
+    avdevice_register_all();
+#endif
 
     if (avformat_network_init()) {
         return 1;

app/src/scrcpy.c

@@ -26,6 +26,7 @@
 #include "stream.h"
 #include "tiny_xpm.h"
 #include "video_buffer.h"
+#include "v4l2sink.h"
 #include "util/log.h"
 #include "util/net.h"
 
@@ -38,6 +39,9 @@ static struct decoder decoder;
 static struct recorder recorder;
 static struct controller controller;
 static struct file_handler file_handler;
+#ifdef V4L2SINK
+static struct v4l2sink v4l2sink;
+#endif
 
 static struct input_manager input_manager = {
     .controller = &controller,
@@ -285,6 +289,12 @@ scrcpy(const struct scrcpy_options *options) {
     bool controller_started = false;
 
     bool record = !!options->record_filename;
+
+#ifdef V4L2SINK
+    bool v4l2sink_initialized = false;
+    bool v4l2 = !!options->v4l2sink_device;
+#endif
+
     struct server_params params = {
         .log_level = options->log_level,
         .crop = options->crop,
@@ -363,9 +373,22 @@ scrcpy(const struct scrcpy_options *options) {
         recorder_initialized = true;
     }
 
+    struct v4l2sink *sink = NULL;
+#ifdef V4L2SINK
+    if (v4l2) {
+        if (!v4l2sink_init(&v4l2sink,
+                           options->v4l2sink_device,
+                           frame_size)) {
+            goto end;
+        }
+        sink = &v4l2sink;
+        v4l2sink_initialized = true;
+    }
+#endif
+
     av_log_set_callback(av_log_callback);
 
-    stream_init(&stream, server.video_socket, dec, rec);
+    stream_init(&stream, server.video_socket, dec, rec, sink);
 
     if (options->display) {
         if (options->control) {
@@ -467,6 +490,12 @@ scrcpy(const struct scrcpy_options *options) {
         recorder_destroy(&recorder);
     }
 
+#ifdef V4L2SINK
+    if (v4l2sink_initialized) {
+        v4l2sink_destroy(&v4l2sink);
+    }
+#endif
+
     if (file_handler_initialized) {
         file_handler_join(&file_handler);
         file_handler_destroy(&file_handler);

app/src/scrcpy.h

@@ -52,6 +52,7 @@ struct scrcpy_options {
     const char *render_driver;
     const char *codec_options;
     const char *encoder_name;
+    const char *v4l2sink_device;
     enum sc_log_level log_level;
     enum sc_record_format record_format;
     struct sc_port_range port_range;
@@ -94,6 +95,7 @@ struct scrcpy_options {
     .render_driver = NULL, \
     .codec_options = NULL, \
     .encoder_name = NULL, \
+    .v4l2sink_device = NULL, \
     .log_level = SC_LOG_LEVEL_INFO, \
     .record_format = SC_RECORD_FORMAT_AUTO, \
     .port_range = { \

app/src/stream.c

@@ -9,6 +9,7 @@
 #include "decoder.h"
 #include "events.h"
 #include "recorder.h"
+#include "v4l2sink.h"
 #include "util/buffer_util.h"
 #include "util/log.h"
 
@@ -89,6 +90,17 @@ process_frame(struct stream *stream, AVPacket *packet) {
         }
     }
 
+#ifdef V4L2SINK
+    if (stream->v4l2sink) {
+        packet->dts = packet->pts;
+
+        if (!v4l2sink_push(stream->v4l2sink, packet)) {
+            LOGE("Could not send packet to v4l2sink");
+            return false;
+        }
+    }
+#endif
+
     return true;
 }
 
@@ -210,6 +222,20 @@ run_stream(void *data) {
         }
     }
 
+#ifdef V4L2SINK
+    if (stream->v4l2sink) {
+        if (!v4l2sink_open(stream->v4l2sink, codec)) {
+            LOGE("Could not open v4l2sink");
+            goto finally_close_decoder;
+        }
+
+        if (!v4l2sink_start(stream->v4l2sink)) {
+            LOGE("Could not start v4l2sink");
+            goto finally_close_v4l2sink;
+        }
+    }
+#endif
+
     stream->parser = av_parser_init(AV_CODEC_ID_H264);
     if (!stream->parser) {
         LOGE("Could not initialize parser");
@@ -253,6 +279,16 @@ run_stream(void *data) {
     if (stream->recorder) {
         recorder_close(stream->recorder);
     }
+#ifdef V4L2SINK
+finally_close_v4l2sink:
+    if (stream->v4l2sink) {
+        v4l2sink_stop(stream->v4l2sink);
+        LOGI("Finishing v4l2sink...");
+        v4l2sink_join(stream->v4l2sink);
+
+        v4l2sink_close(stream->v4l2sink);
+    }
+#endif
 finally_close_decoder:
     if (stream->decoder) {
         decoder_close(stream->decoder);
@@ -266,10 +302,11 @@ run_stream(void *data) {
 
 void
 stream_init(struct stream *stream, socket_t socket,
-            struct decoder *decoder, struct recorder *recorder) {
+            struct decoder *decoder, struct recorder *recorder, struct v4l2sink *v4l2sink) {
     stream->socket = socket;
     stream->decoder = decoder,
     stream->recorder = recorder;
+    stream->v4l2sink = v4l2sink;
     stream->has_pending = false;
 }
 

app/src/stream.h

@@ -18,6 +18,7 @@ struct stream {
     sc_thread thread;
     struct decoder *decoder;
     struct recorder *recorder;
+    struct v4l2sink *v4l2sink;
     AVCodecContext *codec_ctx;
     AVCodecParserContext *parser;
     // successive packets may need to be concatenated, until a non-config
@@ -28,7 +29,7 @@ struct stream {
 
 void
 stream_init(struct stream *stream, socket_t socket,
-            struct decoder *decoder, struct recorder *recorder);
+            struct decoder *decoder, struct recorder *recorder, struct v4l2sink *v4l2sink);
 
 bool
 stream_start(struct stream *stream);