Document v4l2 sink in README

It allows to send the video stream to /dev/videoN, so that it can be
captured (like a webcam) by any V4L2-compatible tool.

Refs #2232 <https://github.com/Genymobile/scrcpy/pull/2232>
Refs #2233 <https://github.com/Genymobile/scrcpy/pull/2233>

Co-authored-by: Romain Vimont <rom@rom1v.com>

README.md

@@ -198,6 +198,7 @@ If `--max-size` is also specified, resizing is applied after cropping.
 To lock the orientation of the mirroring:
 
 ```bash
+scrcpy --lock-video-orientation     # initial (current) orientation
 scrcpy --lock-video-orientation 0   # natural orientation
 scrcpy --lock-video-orientation 1   # 90° counterclockwise
 scrcpy --lock-video-orientation 2   # 180°
@@ -225,7 +226,9 @@ error will give the available encoders:
 scrcpy --encoder _
 ```
 
-### Recording
+### Capture
+
+#### Recording
 
 It is possible to record the screen while mirroring:
 
@@ -249,6 +252,58 @@ variation] does not impact the recorded file.
 [packet delay variation]: https://en.wikipedia.org/wiki/Packet_delay_variation
 
 
+#### v4l2loopback
+
+On Linux, it is possible to send the video stream to a v4l2 loopback device, so
+that the Android device can be opened like a webcam by any v4l2-capable tool.
+
+The module `v4l2loopback` must be installed:
+
+```bash
+sudo apt install v4l2loopback-dkms
+```
+
+To create a v4l2 device:
+
+```bash
+sudo modprobe v4l2loopback
+```
+
+This will create a new video device in `/dev/videoN`, where `N` is an integer
+(more [options](https://github.com/umlaeute/v4l2loopback#options) are available
+to create several devices or devices with specific IDs).
+
+To list the enabled devices:
+
+```bash
+# requires v4l-utils package
+v4l2-ctl --list-devices
+
+# simple but might be sufficient
+ls /dev/video*
+```
+
+To start scrcpy using a v4l2 sink:
+
+```bash
+scrcpy --v4l2-sink=/dev/videoN
+scrcpy --v4l2-sink=/dev/videoN -N  # --no-display to disable mirroring window
+```
+
+(replace `N` by the device ID, check with `ls /dev/video*`)
+
+Once enabled, you can open your video stream with a v4l2-capable tool:
+
+```bash
+ffplay -i /dev/videoN
+vlc v4l2:///dev/videoN   # VLC might add some buffering delay
+```
+
+For example, you could capture the video within [OBS].
+
+[OBS]: https://obsproject.com/
+
+
 ### Connection
 
 #### Wireless

app/meson.build

@@ -33,6 +33,11 @@ else
     src += [ 'src/sys/unix/process.c' ]
 endif
 
+v4l2_support = host_machine.system() == 'linux'
+if v4l2_support
+    src += [ 'src/v4l2_sink.c' ]
+endif
+
 check_functions = [
     'strdup'
 ]
@@ -49,6 +54,10 @@ if not get_option('crossbuild_windows')
         dependency('sdl2'),
     ]
 
+    if v4l2_support
+        dependencies += dependency('libavdevice')
+    endif
+
 else
 
     # cross-compile mingw32 build (from Linux to Windows)
@@ -124,6 +133,9 @@ conf.set('SERVER_DEBUGGER', get_option('server_debugger'))
 # select the debugger method ('old' for Android < 9, 'new' for Android >= 9)
 conf.set('SERVER_DEBUGGER_METHOD_NEW', get_option('server_debugger_method') == 'new')
 
+# enable V4L2 support (linux only)
+conf.set('HAVE_V4L2', v4l2_support)
+
 configure_file(configuration: conf, output: 'config.h')
 
 src_dir = include_directories('src')

app/scrcpy.1

@@ -83,10 +83,12 @@ Inject computer clipboard text as a sequence of key events on Ctrl+v (like MOD+S
 This is a workaround for some devices not behaving as expected when setting the device clipboard programmatically.
 
 .TP
-.BI "\-\-lock\-video\-orientation " value
-Lock video orientation to \fIvalue\fR. Possible values are -1 (unlocked), 0, 1, 2 and 3. Natural device orientation is 0, and each increment adds a 90 degrees otation counterclockwise.
+.BI "\-\-lock\-video\-orientation " [value]
+Lock video orientation to \fIvalue\fR. Possible values are "unlocked", "initial" (locked to the initial orientation), 0, 1, 2 and 3. Natural device orientation is 0, and each increment adds a 90 degrees otation counterclockwise.
 
-Default is -1 (unlocked).
+Default is "unlocked".
+
+Passing the option without argument is equivalent to passing "initial".
 
 .TP
 .BI "\-\-max\-fps " value
@@ -184,8 +186,10 @@ Enable "show touches" on start, restore the initial value on exit.
 It only shows physical touches (not clicks from scrcpy).
 
 .TP
-.B \-v, \-\-version
-Print the version of scrcpy.
+.BI "\-\-v4l2-sink " /dev/videoN
+Output to v4l2loopback device.
+
+It requires to lock the video orientation (see --lock-video-orientation).
 
 .TP
 .BI "\-V, \-\-verbosity " value
@@ -193,6 +197,10 @@ Set the log level ("debug", "info", "warn" or "error").
 
 Default is "info" for release builds, "debug" for debug builds.
 
+.TP
+.B \-v, \-\-version
+Print the version of scrcpy.
+
 .TP
 .B \-w, \-\-stay-awake
 Keep the device on while scrcpy is running, when the device is plugged in.

app/src/cli.c

@@ -79,12 +79,15 @@ scrcpy_print_usage(const char *arg0) {
         "        This is a workaround for some devices not behaving as\n"
         "        expected when setting the device clipboard programmatically.\n"
         "\n"
-        "    --lock-video-orientation value\n"
+        "    --lock-video-orientation [value]\n"
         "        Lock video orientation to value.\n"
-        "        Possible values are -1 (unlocked), 0, 1, 2 and 3.\n"
+        "        Possible values are \"unlocked\", \"initial\" (locked to the\n"
+        "        initial orientation), 0, 1, 2 and 3.\n"
         "        Natural device orientation is 0, and each increment adds a\n"
         "        90 degrees rotation counterclockwise.\n"
-        "        Default is -1 (unlocked).\n"
+        "        Default is \"unlocked\".\n"
+        "        Passing the option without argument is equivalent to passing\n"
+        "        \"initial\".\n"
         "\n"
         "    --max-fps value\n"
         "        Limit the frame rate of screen capture (officially supported\n"
@@ -173,9 +176,13 @@ scrcpy_print_usage(const char *arg0) {
         "        on exit.\n"
         "        It only shows physical touches (not clicks from scrcpy).\n"
         "\n"
-        "    -v, --version\n"
-        "        Print the version of scrcpy.\n"
+#ifdef HAVE_V4L2
+        "    --v4l2-sink /dev/videoN\n"
+        "        Output to v4l2loopback device.\n"
+        "        It requires to lock the video orientation (see\n"
+        "        --lock-video-orientation).\n"
         "\n"
+#endif
         "    -V, --verbosity value\n"
         "        Set the log level (debug, info, warn or error).\n"
 #ifndef NDEBUG
@@ -183,6 +190,9 @@ scrcpy_print_usage(const char *arg0) {
 #else
         "        Default is info.\n"
 #endif
+        "\n"
+        "    -v, --version\n"
+        "        Print the version of scrcpy.\n"
         "\n"
         "    -w, --stay-awake\n"
         "        Keep the device on while scrcpy is running, when the device\n"
@@ -383,15 +393,27 @@ parse_max_fps(const char *s, uint16_t *max_fps) {
 }
 
 static bool
-parse_lock_video_orientation(const char *s, int8_t *lock_video_orientation) {
+parse_lock_video_orientation(const char *s,
+                             enum sc_lock_video_orientation *lock_mode) {
+    if (!s || !strcmp(s, "initial")) {
+        // Without argument, lock the initial orientation
+        *lock_mode = SC_LOCK_VIDEO_ORIENTATION_INITIAL;
+        return true;
+    }
+
+    if (!strcmp(s, "unlocked")) {
+        *lock_mode = SC_LOCK_VIDEO_ORIENTATION_UNLOCKED;
+        return true;
+    }
+
     long value;
-    bool ok = parse_integer_arg(s, &value, false, -1, 3,
+    bool ok = parse_integer_arg(s, &value, false, 0, 3,
                                 "lock video orientation");
     if (!ok) {
         return false;
     }
 
-    *lock_video_orientation = (int8_t) value;
+    *lock_mode = (enum sc_lock_video_orientation) value;
     return true;
 }
 
@@ -661,6 +683,7 @@ 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_V4L2_SINK              1027
 
 bool
 scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
@@ -680,7 +703,7 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
         {"fullscreen",             no_argument,       NULL, 'f'},
         {"help",                   no_argument,       NULL, 'h'},
         {"legacy-paste",           no_argument,       NULL, OPT_LEGACY_PASTE},
-        {"lock-video-orientation", required_argument, NULL,
+        {"lock-video-orientation", optional_argument, NULL,
                                                   OPT_LOCK_VIDEO_ORIENTATION},
         {"max-fps",                required_argument, NULL, OPT_MAX_FPS},
         {"max-size",               required_argument, NULL, 'm'},
@@ -702,6 +725,9 @@ 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 HAVE_V4L2
+        {"v4l2-sink",              required_argument, NULL, OPT_V4L2_SINK},
+#endif
         {"verbosity",              required_argument, NULL, 'V'},
         {"version",                no_argument,       NULL, 'v'},
         {"window-title",           required_argument, NULL, OPT_WINDOW_TITLE},
@@ -765,7 +791,8 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
                 }
                 break;
             case OPT_LOCK_VIDEO_ORIENTATION:
-                if (!parse_lock_video_orientation(optarg, &opts->lock_video_orientation)) {
+                if (!parse_lock_video_orientation(optarg,
+                        &opts->lock_video_orientation)) {
                     return false;
                 }
                 break;
@@ -885,16 +912,36 @@ 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 HAVE_V4L2
+            case OPT_V4L2_SINK:
+                opts->v4l2_device = optarg;
+                break;
+#endif
             default:
                 // getopt prints the error message on stderr
                 return false;
         }
     }
 
+#ifdef HAVE_V4L2
+    if (!opts->display && !opts->record_filename && !opts->v4l2_device) {
+        LOGE("-N/--no-display requires either screen recording (-r/--record)"
+             " or sink to v4l2loopback device (--v4l2-sink)");
+        return false;
+    }
+
+    if (opts->v4l2_device && opts->lock_video_orientation
+                             == SC_LOCK_VIDEO_ORIENTATION_UNLOCKED) {
+        LOGI("Video orientation is locked for v4l2 sink. "
+             "See --lock-video-orientation.");
+        opts->lock_video_orientation = SC_LOCK_VIDEO_ORIENTATION_INITIAL;
+    }
+#else
     if (!opts->display && !opts->record_filename) {
         LOGE("-N/--no-display requires screen recording (-r/--record)");
         return false;
     }
+#endif
 
     int index = optind;
     if (index < argc) {

app/src/control_msg.c

@@ -67,6 +67,9 @@ control_msg_serialize(const struct control_msg *msg, unsigned char *buf) {
             buffer_write32be(&buf[17],
                              (uint32_t) msg->inject_scroll_event.vscroll);
             return 21;
+        case CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON:
+            buf[1] = msg->inject_keycode.action;
+            return 2;
         case CONTROL_MSG_TYPE_SET_CLIPBOARD: {
             buf[1] = !!msg->set_clipboard.paste;
             size_t len = write_string(msg->set_clipboard.text,
@@ -77,7 +80,6 @@ control_msg_serialize(const struct control_msg *msg, unsigned char *buf) {
         case CONTROL_MSG_TYPE_SET_SCREEN_POWER_MODE:
             buf[1] = msg->set_screen_power_mode.mode;
             return 2;
-        case CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON:
         case CONTROL_MSG_TYPE_EXPAND_NOTIFICATION_PANEL:
         case CONTROL_MSG_TYPE_COLLAPSE_NOTIFICATION_PANEL:
         case CONTROL_MSG_TYPE_GET_CLIPBOARD:

app/src/control_msg.h

@@ -64,6 +64,10 @@ struct control_msg {
             int32_t hscroll;
             int32_t vscroll;
         } inject_scroll_event;
+        struct {
+            enum android_keyevent_action action; // action for the BACK key
+            // screen may only be turned on on ACTION_DOWN
+        } back_or_screen_on;
         struct {
             char *text; // owned, to be freed by free()
             bool paste;

app/src/decoder.c

@@ -64,6 +64,7 @@ decoder_open(struct decoder *decoder, const AVCodec *codec) {
         av_frame_free(&decoder->frame);
         avcodec_close(decoder->codec_ctx);
         avcodec_free_context(&decoder->codec_ctx);
+        return false;
     }
 
     return true;
@@ -98,8 +99,8 @@ decoder_push(struct decoder *decoder, const AVPacket *packet) {
         return true;
     }
 
-    int ret;
-    if ((ret = avcodec_send_packet(decoder->codec_ctx, packet)) < 0) {
+    int ret = avcodec_send_packet(decoder->codec_ctx, packet);
+    if (ret < 0 && ret != AVERROR(EAGAIN)) {
         LOGE("Could not send video packet: %d", ret);
         return false;
     }

app/src/decoder.h

@@ -8,7 +8,7 @@
 #include <stdbool.h>
 #include <libavformat/avformat.h>
 
-#define DECODER_MAX_SINKS 1
+#define DECODER_MAX_SINKS 2
 
 struct decoder {
     struct sc_packet_sink packet_sink; // packet sink trait

app/src/input_manager.c

@@ -146,13 +146,25 @@ action_cut(struct controller *controller, int actions) {
 }
 
 // turn the screen on if it was off, press BACK otherwise
+// If the screen is off, it is turned on only on ACTION_DOWN
 static void
-press_back_or_turn_screen_on(struct controller *controller) {
+press_back_or_turn_screen_on(struct controller *controller, int actions) {
     struct control_msg msg;
     msg.type = CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON;
 
-    if (!controller_push_msg(controller, &msg)) {
-        LOGW("Could not request 'press back or turn screen on'");
+    if (actions & ACTION_DOWN) {
+        msg.back_or_screen_on.action = AKEY_EVENT_ACTION_DOWN;
+        if (!controller_push_msg(controller, &msg)) {
+            LOGW("Could not request 'press back or turn screen on'");
+            return;
+        }
+    }
+
+    if (actions & ACTION_UP) {
+        msg.back_or_screen_on.action = AKEY_EVENT_ACTION_UP;
+        if (!controller_push_msg(controller, &msg)) {
+            LOGW("Could not request 'press back or turn screen on'");
+        }
     }
 }
 
@@ -646,13 +658,23 @@ input_manager_process_mouse_button(struct input_manager *im,
     }
 
     bool down = event->type == SDL_MOUSEBUTTONDOWN;
-    if (!im->forward_all_clicks && down) {
+    if (!im->forward_all_clicks) {
+        int action = down ? ACTION_DOWN : ACTION_UP;
+
+        if (control && event->button == SDL_BUTTON_X1) {
+            action_app_switch(im->controller, action);
+            return;
+        }
+        if (control && event->button == SDL_BUTTON_X2 && down) {
+            expand_notification_panel(im->controller);
+            return;
+        }
         if (control && event->button == SDL_BUTTON_RIGHT) {
-            press_back_or_turn_screen_on(im->controller);
+            press_back_or_turn_screen_on(im->controller, action);
             return;
         }
         if (control && event->button == SDL_BUTTON_MIDDLE) {
-            action_home(im->controller, ACTION_DOWN | ACTION_UP);
+            action_home(im->controller, action);
             return;
         }
 
@@ -665,7 +687,9 @@ input_manager_process_mouse_button(struct input_manager *im,
             bool outside = x < r->x || x >= r->x + r->w
                         || y < r->y || y >= r->y + r->h;
             if (outside) {
-                screen_resize_to_fit(im->screen);
+                if (down) {
+                    screen_resize_to_fit(im->screen);
+                }
                 return;
             }
         }

app/src/main.c

@@ -6,6 +6,9 @@
 #include <stdbool.h>
 #include <unistd.h>
 #include <libavformat/avformat.h>
+#ifdef HAVE_V4L2
+# 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 HAVE_V4L2
+    fprintf(stderr, " - libavdevice %d.%d.%d\n", LIBAVDEVICE_VERSION_MAJOR,
+                                                 LIBAVDEVICE_VERSION_MINOR,
+                                                 LIBAVDEVICE_VERSION_MICRO);
+#endif
 }
 
 static SDL_LogPriority
@@ -90,6 +98,12 @@ main(int argc, char *argv[]) {
     av_register_all();
 #endif
 
+#ifdef HAVE_V4L2
+    if (args.opts.v4l2_device) {
+        avdevice_register_all();
+    }
+#endif
+
     if (avformat_network_init()) {
         return 1;
     }

app/src/recorder.c

@@ -4,6 +4,7 @@
 #include <libavutil/time.h>
 
 #include "util/log.h"
+#include "util/str_util.h"
 
 /** Downcast packet_sink to recorder */
 #define DOWNCAST(SINK) container_of(SINK, struct recorder, packet_sink)
@@ -22,8 +23,8 @@ find_muxer(const char *name) {
 #else
         oformat = av_oformat_next(oformat);
 #endif
-        // until null or with name "mp4"
-    } while (oformat && strcmp(oformat->name, name));
+        // until null or containing the requested name
+    } while (oformat && !strlist_contains(oformat->name, ',', name));
     return oformat;
 }
 
@@ -218,18 +219,36 @@ run_recorder(void *data) {
 
 static bool
 recorder_open(struct recorder *recorder, const AVCodec *input_codec) {
+    bool ok = sc_mutex_init(&recorder->mutex);
+    if (!ok) {
+        LOGC("Could not create mutex");
+        return false;
+    }
+
+    ok = sc_cond_init(&recorder->queue_cond);
+    if (!ok) {
+        LOGC("Could not create cond");
+        goto error_mutex_destroy;
+    }
+
+    queue_init(&recorder->queue);
+    recorder->stopped = false;
+    recorder->failed = false;
+    recorder->header_written = false;
+    recorder->previous = NULL;
+
     const char *format_name = recorder_get_format_name(recorder->format);
     assert(format_name);
     const AVOutputFormat *format = find_muxer(format_name);
     if (!format) {
         LOGE("Could not find muxer");
-        return false;
+        goto error_cond_destroy;
     }
 
     recorder->ctx = avformat_alloc_context();
     if (!recorder->ctx) {
         LOGE("Could not allocate output context");
-        return false;
+        goto error_cond_destroy;
     }
 
     // contrary to the deprecated API (av_oformat_next()), av_muxer_iterate()
@@ -243,8 +262,7 @@ recorder_open(struct recorder *recorder, const AVCodec *input_codec) {
 
     AVStream *ostream = avformat_new_stream(recorder->ctx, input_codec);
     if (!ostream) {
-        avformat_free_context(recorder->ctx);
-        return false;
+        goto error_avformat_free_context;
     }
 
     ostream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
@@ -258,22 +276,31 @@ recorder_open(struct recorder *recorder, const AVCodec *input_codec) {
     if (ret < 0) {
         LOGE("Failed to open output file: %s", recorder->filename);
         // ostream will be cleaned up during context cleaning
-        avformat_free_context(recorder->ctx);
-        return false;
+        goto error_avformat_free_context;
     }
 
     LOGD("Starting recorder thread");
-    bool ok = sc_thread_create(&recorder->thread, run_recorder, "recorder",
+    ok = sc_thread_create(&recorder->thread, run_recorder, "recorder",
                                recorder);
     if (!ok) {
         LOGC("Could not start recorder thread");
-        avformat_free_context(recorder->ctx);
-        return false;
+        goto error_avio_close;
     }
 
     LOGI("Recording started to %s file: %s", format_name, recorder->filename);
 
     return true;
+
+error_avio_close:
+    avio_close(recorder->ctx->pb);
+error_avformat_free_context:
+    avformat_free_context(recorder->ctx);
+error_cond_destroy:
+    sc_cond_destroy(&recorder->queue_cond);
+error_mutex_destroy:
+    sc_mutex_destroy(&recorder->mutex);
+
+    return false;
 }
 
 static void
@@ -287,6 +314,8 @@ recorder_close(struct recorder *recorder) {
 
     avio_close(recorder->ctx->pb);
     avformat_free_context(recorder->ctx);
+    sc_cond_destroy(&recorder->queue_cond);
+    sc_mutex_destroy(&recorder->mutex);
 }
 
 static bool
@@ -343,28 +372,8 @@ recorder_init(struct recorder *recorder,
         return false;
     }
 
-    bool ok = sc_mutex_init(&recorder->mutex);
-    if (!ok) {
-        LOGC("Could not create mutex");
-        free(recorder->filename);
-        return false;
-    }
-
-    ok = sc_cond_init(&recorder->queue_cond);
-    if (!ok) {
-        LOGC("Could not create cond");
-        sc_mutex_destroy(&recorder->mutex);
-        free(recorder->filename);
-        return false;
-    }
-
-    queue_init(&recorder->queue);
-    recorder->stopped = false;
-    recorder->failed = false;
     recorder->format = format;
     recorder->declared_frame_size = declared_frame_size;
-    recorder->header_written = false;
-    recorder->previous = NULL;
 
     static const struct sc_packet_sink_ops ops = {
         .open = recorder_packet_sink_open,
@@ -379,7 +388,5 @@ recorder_init(struct recorder *recorder,
 
 void
 recorder_destroy(struct recorder *recorder) {
-    sc_cond_destroy(&recorder->queue_cond);
-    sc_mutex_destroy(&recorder->mutex);
     free(recorder->filename);
 }

app/src/scrcpy.c

@@ -27,6 +27,9 @@
 #include "tiny_xpm.h"
 #include "util/log.h"
 #include "util/net.h"
+#ifdef HAVE_V4L2
+# include "v4l2_sink.h"
+#endif
 
 static struct server server;
 static struct screen screen;
@@ -34,6 +37,9 @@ static struct fps_counter fps_counter;
 static struct stream stream;
 static struct decoder decoder;
 static struct recorder recorder;
+#ifdef HAVE_V4L2
+static struct sc_v4l2_sink v4l2_sink;
+#endif
 static struct controller controller;
 static struct file_handler file_handler;
 
@@ -126,30 +132,6 @@ sdl_init_and_configure(bool display, const char *render_driver,
     return true;
 }
 
-
-#if defined(__APPLE__) || defined(__WINDOWS__)
-# define CONTINUOUS_RESIZING_WORKAROUND
-#endif
-
-#ifdef CONTINUOUS_RESIZING_WORKAROUND
-// On Windows and MacOS, resizing blocks the event loop, so resizing events are
-// not triggered. As a workaround, handle them in an event handler.
-//
-// <https://bugzilla.libsdl.org/show_bug.cgi?id=2077>
-// <https://stackoverflow.com/a/40693139/1987178>
-static int
-event_watcher(void *data, SDL_Event *event) {
-    (void) data;
-    if (event->type == SDL_WINDOWEVENT
-            && event->window.event == SDL_WINDOWEVENT_RESIZED) {
-        // In practice, it seems to always be called from the same thread in
-        // that specific case. Anyway, it's just a workaround.
-        screen_render(&screen, true);
-    }
-    return 0;
-}
-#endif
-
 static bool
 is_apk(const char *file) {
     const char *ext = strrchr(file, '.');
@@ -189,7 +171,7 @@ handle_event(SDL_Event *event, const struct scrcpy_options *options) {
                 action = ACTION_PUSH_FILE;
             }
             file_handler_request(&file_handler, action, file);
-            break;
+            goto end;
         }
     }
 
@@ -207,11 +189,6 @@ end:
 
 static bool
 event_loop(const struct scrcpy_options *options) {
-#ifdef CONTINUOUS_RESIZING_WORKAROUND
-    if (options->display) {
-        SDL_AddEventWatch(event_watcher, NULL);
-    }
-#endif
     SDL_Event event;
     while (SDL_WaitEvent(&event)) {
         enum event_result result = handle_event(&event, options);
@@ -276,6 +253,9 @@ scrcpy(const struct scrcpy_options *options) {
     bool fps_counter_initialized = false;
     bool file_handler_initialized = false;
     bool recorder_initialized = false;
+#ifdef HAVE_V4L2
+    bool v4l2_sink_initialized = false;
+#endif
     bool stream_started = false;
     bool controller_initialized = false;
     bool controller_started = false;
@@ -324,7 +304,6 @@ scrcpy(const struct scrcpy_options *options) {
         goto end;
     }
 
-    struct decoder *dec = NULL;
     if (options->display) {
         if (!fps_counter_init(&fps_counter)) {
             goto end;
@@ -338,7 +317,14 @@ scrcpy(const struct scrcpy_options *options) {
             }
             file_handler_initialized = true;
         }
+    }
 
+    struct decoder *dec = NULL;
+    bool needs_decoder = options->display;
+#ifdef HAVE_V4L2
+    needs_decoder |= !!options->v4l2_device;
+#endif
+    if (needs_decoder) {
         decoder_init(&decoder);
         dec = &decoder;
     }
@@ -394,6 +380,7 @@ scrcpy(const struct scrcpy_options *options) {
             .window_borderless = options->window_borderless,
             .rotation = options->rotation,
             .mipmaps = options->mipmaps,
+            .fullscreen = options->fullscreen,
         };
 
         if (!screen_init(&screen, &fps_counter, &screen_params)) {
@@ -412,12 +399,20 @@ scrcpy(const struct scrcpy_options *options) {
                 LOGW("Could not request 'set screen power mode'");
             }
         }
-
-        if (options->fullscreen) {
-            screen_switch_fullscreen(&screen);
-        }
     }
 
+#ifdef HAVE_V4L2
+    if (options->v4l2_device) {
+        if (!sc_v4l2_sink_init(&v4l2_sink, options->v4l2_device, frame_size)) {
+            goto end;
+        }
+
+        decoder_add_sink(&decoder, &v4l2_sink.frame_sink);
+
+        v4l2_sink_initialized = true;
+    }
+#endif
+
     // now we consumed the header values, the socket receives the video stream
     // start the stream
     if (!stream_start(&stream)) {
@@ -430,6 +425,10 @@ scrcpy(const struct scrcpy_options *options) {
     ret = event_loop(options);
     LOGD("quit...");
 
+    // Close the window immediately on closing, because screen_destroy() may
+    // only be called once the stream thread is joined (it may take time)
+    screen_hide_window(&screen);
+
 end:
     // The stream is not stopped explicitly, because it will stop by itself on
     // end-of-stream
@@ -454,6 +453,12 @@ end:
         stream_join(&stream);
     }
 
+#ifdef HAVE_V4L2
+    if (v4l2_sink_initialized) {
+        sc_v4l2_sink_destroy(&v4l2_sink);
+    }
+#endif
+
     // Destroy the screen only after the stream is guaranteed to be finished,
     // because otherwise the screen could receive new frames after destruction
     if (screen_initialized) {

app/src/scrcpy.h

@@ -20,6 +20,16 @@ enum sc_record_format {
     SC_RECORD_FORMAT_MKV,
 };
 
+enum sc_lock_video_orientation {
+    SC_LOCK_VIDEO_ORIENTATION_UNLOCKED = -1,
+    // lock the current orientation when scrcpy starts
+    SC_LOCK_VIDEO_ORIENTATION_INITIAL = -2,
+    SC_LOCK_VIDEO_ORIENTATION_0 = 0,
+    SC_LOCK_VIDEO_ORIENTATION_1,
+    SC_LOCK_VIDEO_ORIENTATION_2,
+    SC_LOCK_VIDEO_ORIENTATION_3,
+};
+
 #define SC_MAX_SHORTCUT_MODS 8
 
 enum sc_shortcut_mod {
@@ -52,6 +62,7 @@ struct scrcpy_options {
     const char *render_driver;
     const char *codec_options;
     const char *encoder_name;
+    const char *v4l2_device;
     enum sc_log_level log_level;
     enum sc_record_format record_format;
     struct sc_port_range port_range;
@@ -59,7 +70,7 @@ struct scrcpy_options {
     uint16_t max_size;
     uint32_t bit_rate;
     uint16_t max_fps;
-    int8_t lock_video_orientation;
+    enum sc_lock_video_orientation lock_video_orientation;
     uint8_t rotation;
     int16_t window_x; // SC_WINDOW_POSITION_UNDEFINED for "auto"
     int16_t window_y; // SC_WINDOW_POSITION_UNDEFINED for "auto"
@@ -93,6 +104,7 @@ struct scrcpy_options {
     .render_driver = NULL, \
     .codec_options = NULL, \
     .encoder_name = NULL, \
+    .v4l2_device = NULL, \
     .log_level = SC_LOG_LEVEL_INFO, \
     .record_format = SC_RECORD_FORMAT_AUTO, \
     .port_range = { \
@@ -106,7 +118,7 @@ struct scrcpy_options {
     .max_size = 0, \
     .bit_rate = DEFAULT_BIT_RATE, \
     .max_fps = 0, \
-    .lock_video_orientation = -1, \
+    .lock_video_orientation = SC_LOCK_VIDEO_ORIENTATION_UNLOCKED, \
     .rotation = 0, \
     .window_x = SC_WINDOW_POSITION_UNDEFINED, \
     .window_y = SC_WINDOW_POSITION_UNDEFINED, \

app/src/screen.c

@@ -220,6 +220,29 @@ create_texture(struct screen *screen) {
     return texture;
 }
 
+#if defined(__APPLE__) || defined(__WINDOWS__)
+# define CONTINUOUS_RESIZING_WORKAROUND
+#endif
+
+#ifdef CONTINUOUS_RESIZING_WORKAROUND
+// On Windows and MacOS, resizing blocks the event loop, so resizing events are
+// not triggered. As a workaround, handle them in an event handler.
+//
+// <https://bugzilla.libsdl.org/show_bug.cgi?id=2077>
+// <https://stackoverflow.com/a/40693139/1987178>
+static int
+event_watcher(void *data, SDL_Event *event) {
+    struct screen *screen = data;
+    if (event->type == SDL_WINDOWEVENT
+            && event->window.event == SDL_WINDOWEVENT_RESIZED) {
+        // In practice, it seems to always be called from the same thread in
+        // that specific case. Anyway, it's just a workaround.
+        screen_render(screen, true);
+    }
+    return 0;
+}
+#endif
+
 static bool
 screen_frame_sink_open(struct sc_frame_sink *sink) {
     struct screen *screen = DOWNCAST(sink);
@@ -402,6 +425,14 @@ screen_init(struct screen *screen, struct fps_counter *fps_counter,
 
     screen_update_content_rect(screen);
 
+    if (params->fullscreen) {
+        screen_switch_fullscreen(screen);
+    }
+
+#ifdef CONTINUOUS_RESIZING_WORKAROUND
+    SDL_AddEventWatch(event_watcher, screen);
+#endif
+
     static const struct sc_frame_sink_ops ops = {
         .open = screen_frame_sink_open,
         .close = screen_frame_sink_close,
@@ -417,11 +448,16 @@ screen_init(struct screen *screen, struct fps_counter *fps_counter,
     return true;
 }
 
-void
+static void
 screen_show_window(struct screen *screen) {
     SDL_ShowWindow(screen->window);
 }
 
+void
+screen_hide_window(struct screen *screen) {
+    SDL_HideWindow(screen->window);
+}
+
 void
 screen_destroy(struct screen *screen) {
 #ifndef NDEBUG

app/src/screen.h

@@ -12,8 +12,6 @@
 #include "trait/frame_sink.h"
 #include "video_buffer.h"
 
-struct video_buffer;
-
 struct screen {
     struct sc_frame_sink frame_sink; // frame sink trait
 
@@ -62,6 +60,8 @@ struct screen_params {
 
     uint8_t rotation;
     bool mipmaps;
+
+    bool fullscreen;
 };
 
 // initialize screen, create window, renderer and texture (window is hidden)
@@ -69,14 +69,17 @@ bool
 screen_init(struct screen *screen, struct fps_counter *fps_counter,
             const struct screen_params *params);
 
-// show the window
-void
-screen_show_window(struct screen *screen);
-
 // destroy window, renderer and texture (if any)
 void
 screen_destroy(struct screen *screen);
 
+// hide the window
+//
+// It is used to hide the window immediately on closing without waiting for
+// screen_destroy()
+void
+screen_hide_window(struct screen *screen);
+
 // render the texture to the renderer
 //
 // Set the update_content_rect flag if the window or content size may have

app/src/trait/frame_sink.h

@@ -6,6 +6,8 @@
 #include <assert.h>
 #include <stdbool.h>
 
+typedef struct AVFrame AVFrame;
+
 /**
  * Frame sink trait.
  *

app/src/trait/packet_sink.h

@@ -5,7 +5,9 @@
 
 #include <assert.h>
 #include <stdbool.h>
-#include <libavcodec/avcodec.h>
+
+typedef struct AVCodec AVCodec;
+typedef struct AVPacket AVPacket;
 
 /**
  * Packet sink trait.

app/src/util/str_util.c

@@ -140,6 +140,24 @@ parse_integer_with_suffix(const char *s, long *out) {
     return true;
 }
 
+bool
+strlist_contains(const char *list, char sep, const char *s) {
+    char *p;
+    do {
+        p = strchr(list, sep);
+
+        size_t token_len = p ? (size_t) (p - list) : strlen(list);
+        if (!strncmp(list, s, token_len)) {
+            return true;
+        }
+
+        if (p) {
+            list = p + 1;
+        }
+    } while (p);
+    return false;
+}
+
 size_t
 utf8_truncation_index(const char *utf8, size_t max_len) {
     size_t len = strlen(utf8);

app/src/util/str_util.h

@@ -43,6 +43,11 @@ parse_integers(const char *s, const char sep, size_t max_items, long *out);
 bool
 parse_integer_with_suffix(const char *s, long *out);
 
+// search s in the list separated by sep
+// for example, strlist_contains("a,bc,def", ',', "bc") returns true
+bool
+strlist_contains(const char *list, char sep, const char *s);
+
 // return the index to truncate a UTF-8 string at a valid position
 size_t
 utf8_truncation_index(const char *utf8, size_t max_len);

app/src/v4l2_sink.c

@@ -0,0 +1,341 @@
+#include "v4l2_sink.h"
+
+#include "util/log.h"
+#include "util/str_util.h"
+
+/** Downcast frame_sink to sc_v4l2_sink */
+#define DOWNCAST(SINK) container_of(SINK, struct sc_v4l2_sink, frame_sink)
+
+static const AVRational SCRCPY_TIME_BASE = {1, 1000000}; // timestamps in us
+
+static const AVOutputFormat *
+find_muxer(const char *name) {
+#ifdef SCRCPY_LAVF_HAS_NEW_MUXER_ITERATOR_API
+    void *opaque = NULL;
+#endif
+    const AVOutputFormat *oformat = NULL;
+    do {
+#ifdef SCRCPY_LAVF_HAS_NEW_MUXER_ITERATOR_API
+        oformat = av_muxer_iterate(&opaque);
+#else
+        oformat = av_oformat_next(oformat);
+#endif
+        // until null or containing the requested name
+    } while (oformat && !strlist_contains(oformat->name, ',', name));
+    return oformat;
+}
+
+static bool
+write_header(struct sc_v4l2_sink *vs, const AVPacket *packet) {
+    AVStream *ostream = vs->format_ctx->streams[0];
+
+    uint8_t *extradata = av_malloc(packet->size * sizeof(uint8_t));
+    if (!extradata) {
+        LOGC("Could not allocate extradata");
+        return false;
+    }
+
+    // copy the first packet to the extra data
+    memcpy(extradata, packet->data, packet->size);
+
+    ostream->codecpar->extradata = extradata;
+    ostream->codecpar->extradata_size = packet->size;
+
+    int ret = avformat_write_header(vs->format_ctx, NULL);
+    if (ret < 0) {
+        LOGE("Failed to write header to %s", vs->device_name);
+        return false;
+    }
+
+    return true;
+}
+
+static void
+rescale_packet(struct sc_v4l2_sink *vs, AVPacket *packet) {
+    AVStream *ostream = vs->format_ctx->streams[0];
+    av_packet_rescale_ts(packet, SCRCPY_TIME_BASE, ostream->time_base);
+}
+
+static bool
+write_packet(struct sc_v4l2_sink *vs, AVPacket *packet) {
+    if (!vs->header_written) {
+        bool ok = write_header(vs, packet);
+        if (!ok) {
+            return false;
+        }
+        vs->header_written = true;
+        return true;
+    }
+
+    rescale_packet(vs, packet);
+
+    bool ok = av_write_frame(vs->format_ctx, packet) >= 0;
+
+    // Failing to write the last frame is not very serious, no future frame may
+    // depend on it, so the resulting file will still be valid
+    (void) ok;
+
+    return true;
+}
+
+static bool
+encode_and_write_frame(struct sc_v4l2_sink *vs, const AVFrame *frame) {
+    int ret = avcodec_send_frame(vs->encoder_ctx, frame);
+    if (ret < 0 && ret != AVERROR(EAGAIN)) {
+        LOGE("Could not send v4l2 video frame: %d", ret);
+        return false;
+    }
+
+    AVPacket *packet = &vs->packet;
+    ret = avcodec_receive_packet(vs->encoder_ctx, packet);
+    if (ret == 0) {
+        // A packet was received
+
+        bool ok = write_packet(vs, packet);
+        if (!ok) {
+            LOGW("Could not send packet to v4l2 sink");
+            return false;
+        }
+        av_packet_unref(packet);
+    } else if (ret != AVERROR(EAGAIN)) {
+        LOGE("Could not receive v4l2 video packet: %d", ret);
+        return false;
+    }
+
+    return true;
+}
+
+static int
+run_v4l2_sink(void *data) {
+    struct sc_v4l2_sink *vs = data;
+
+    for (;;) {
+        sc_mutex_lock(&vs->mutex);
+
+        while (!vs->stopped && vs->vb.pending_frame_consumed) {
+            sc_cond_wait(&vs->cond, &vs->mutex);
+        }
+
+        if (vs->stopped) {
+            sc_mutex_unlock(&vs->mutex);
+            break;
+        }
+
+        sc_mutex_unlock(&vs->mutex);
+
+        video_buffer_consume(&vs->vb, vs->frame);
+        bool ok = encode_and_write_frame(vs, vs->frame);
+        if (!ok) {
+            LOGE("Could not send frame to v4l2 sink");
+            break;
+        }
+    }
+
+    LOGD("V4l2 thread ended");
+
+    return 0;
+}
+
+static bool
+sc_v4l2_sink_open(struct sc_v4l2_sink *vs) {
+    bool ok = video_buffer_init(&vs->vb);
+    if (!ok) {
+        return false;
+    }
+
+    ok = sc_mutex_init(&vs->mutex);
+    if (!ok) {
+        LOGC("Could not create mutex");
+        goto error_video_buffer_destroy;
+    }
+
+    ok = sc_cond_init(&vs->cond);
+    if (!ok) {
+        LOGC("Could not create cond");
+        goto error_mutex_destroy;
+    }
+
+    // FIXME
+    const AVOutputFormat *format = find_muxer("video4linux2,v4l2");
+    if (!format) {
+        LOGE("Could not find v4l2 muxer");
+        goto error_cond_destroy;
+    }
+
+    const AVCodec *encoder = avcodec_find_encoder(AV_CODEC_ID_RAWVIDEO);
+    if (!encoder) {
+        LOGE("Raw video encoder not found");
+        return false;
+    }
+
+    vs->format_ctx = avformat_alloc_context();
+    if (!vs->format_ctx) {
+        LOGE("Could not allocate v4l2 output context");
+        return false;
+    }
+
+    // contrary to the deprecated API (av_oformat_next()), av_muxer_iterate()
+    // returns (on purpose) a pointer-to-const, but AVFormatContext.oformat
+    // still expects a pointer-to-non-const (it has not be updated accordingly)
+    // <https://github.com/FFmpeg/FFmpeg/commit/0694d8702421e7aff1340038559c438b61bb30dd>
+    vs->format_ctx->oformat = (AVOutputFormat *) format;
+    vs->format_ctx->url = strdup(vs->device_name);
+    if (!vs->format_ctx->url) {
+        LOGE("Could not strdup v4l2 device name");
+        goto error_avformat_free_context;
+        return false;
+    }
+
+    AVStream *ostream = avformat_new_stream(vs->format_ctx, encoder);
+    if (!ostream) {
+        LOGE("Could not allocate new v4l2 stream");
+        goto error_avformat_free_context;
+        return false;
+    }
+
+    ostream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
+    ostream->codecpar->codec_id = encoder->id;
+    ostream->codecpar->format = AV_PIX_FMT_YUV420P;
+    ostream->codecpar->width = vs->frame_size.width;
+    ostream->codecpar->height = vs->frame_size.height;
+
+    int ret = avio_open(&vs->format_ctx->pb, vs->device_name, AVIO_FLAG_WRITE);
+    if (ret < 0) {
+        LOGE("Failed to open output device: %s", vs->device_name);
+        // ostream will be cleaned up during context cleaning
+        goto error_avformat_free_context;
+    }
+
+    vs->encoder_ctx = avcodec_alloc_context3(encoder);
+    if (!vs->encoder_ctx) {
+        LOGC("Could not allocate codec context for v4l2");
+        goto error_avio_close;
+    }
+
+    vs->encoder_ctx->width = vs->frame_size.width;
+    vs->encoder_ctx->height = vs->frame_size.height;
+    vs->encoder_ctx->pix_fmt = AV_PIX_FMT_YUV420P;
+    vs->encoder_ctx->time_base.num = 1;
+    vs->encoder_ctx->time_base.den = 1;
+
+    if (avcodec_open2(vs->encoder_ctx, encoder, NULL) < 0) {
+        LOGE("Could not open codec for v4l2");
+        goto error_avcodec_free_context;
+    }
+
+    vs->frame = av_frame_alloc();
+    if (!vs->frame) {
+        LOGE("Could not create v4l2 frame");
+        goto error_avcodec_close;
+    }
+
+    LOGD("Starting v4l2 thread");
+    ok = sc_thread_create(&vs->thread, run_v4l2_sink, "v4l2", vs);
+    if (!ok) {
+        LOGC("Could not start v4l2 thread");
+        goto error_av_frame_free;
+    }
+
+    vs->header_written = false;
+    vs->stopped = false;
+
+    LOGI("v4l2 sink started to device: %s", vs->device_name);
+
+    return true;
+
+error_av_frame_free:
+    av_frame_free(&vs->frame);
+error_avcodec_close:
+    avcodec_close(vs->encoder_ctx);
+error_avcodec_free_context:
+    avcodec_free_context(&vs->encoder_ctx);
+error_avio_close:
+    avio_close(vs->format_ctx->pb);
+error_avformat_free_context:
+    avformat_free_context(vs->format_ctx);
+error_cond_destroy:
+    sc_cond_destroy(&vs->cond);
+error_mutex_destroy:
+    sc_mutex_destroy(&vs->mutex);
+error_video_buffer_destroy:
+    video_buffer_destroy(&vs->vb);
+
+    return false;
+}
+
+static void
+sc_v4l2_sink_close(struct sc_v4l2_sink *vs) {
+    sc_mutex_lock(&vs->mutex);
+    vs->stopped = true;
+    sc_cond_signal(&vs->cond);
+    sc_mutex_unlock(&vs->mutex);
+
+    sc_thread_join(&vs->thread, NULL);
+
+    av_frame_free(&vs->frame);
+    avcodec_close(vs->encoder_ctx);
+    avcodec_free_context(&vs->encoder_ctx);
+    avio_close(vs->format_ctx->pb);
+    avformat_free_context(vs->format_ctx);
+    sc_cond_destroy(&vs->cond);
+    sc_mutex_destroy(&vs->mutex);
+    video_buffer_destroy(&vs->vb);
+}
+
+static bool
+sc_v4l2_sink_push(struct sc_v4l2_sink *vs, const AVFrame *frame) {
+    bool ok = video_buffer_push(&vs->vb, frame, NULL);
+    if (!ok) {
+        return false;
+    }
+
+    // signal possible change of vs->vb.pending_frame_consumed
+    sc_cond_signal(&vs->cond);
+
+    return true;
+}
+
+static bool
+sc_v4l2_frame_sink_open(struct sc_frame_sink *sink) {
+    struct sc_v4l2_sink *vs = DOWNCAST(sink);
+    return sc_v4l2_sink_open(vs);
+}
+
+static void
+sc_v4l2_frame_sink_close(struct sc_frame_sink *sink) {
+    struct sc_v4l2_sink *vs = DOWNCAST(sink);
+    sc_v4l2_sink_close(vs);
+}
+
+static bool
+sc_v4l2_frame_sink_push(struct sc_frame_sink *sink, const AVFrame *frame) {
+    struct sc_v4l2_sink *vs = DOWNCAST(sink);
+    return sc_v4l2_sink_push(vs, frame);
+}
+
+bool
+sc_v4l2_sink_init(struct sc_v4l2_sink *vs, const char *device_name,
+                  struct size frame_size) {
+    vs->device_name = strdup(device_name);
+    if (!vs->device_name) {
+        LOGE("Could not strdup v4l2 device name");
+        return false;
+    }
+
+    vs->frame_size = frame_size;
+
+    static const struct sc_frame_sink_ops ops = {
+        .open = sc_v4l2_frame_sink_open,
+        .close = sc_v4l2_frame_sink_close,
+        .push = sc_v4l2_frame_sink_push,
+    };
+
+    vs->frame_sink.ops = &ops;
+
+    return true;
+}
+
+void
+sc_v4l2_sink_destroy(struct sc_v4l2_sink *vs) {
+    free(vs->device_name);
+}

app/src/v4l2_sink.h

@@ -0,0 +1,39 @@
+#ifndef SC_V4L2_SINK_H
+#define SC_V4L2_SINK_H
+
+#include "common.h"
+
+#include "coords.h"
+#include "trait/frame_sink.h"
+#include "video_buffer.h"
+
+#include <libavformat/avformat.h>
+
+struct sc_v4l2_sink {
+    struct sc_frame_sink frame_sink; // frame sink trait
+
+    struct video_buffer vb;
+    AVFormatContext *format_ctx;
+    AVCodecContext *encoder_ctx;
+
+    char *device_name;
+    struct size frame_size;
+
+    sc_thread thread;
+    sc_mutex mutex;
+    sc_cond cond;
+    bool stopped;
+    bool header_written;
+
+    AVFrame *frame;
+    AVPacket packet;
+};
+
+bool
+sc_v4l2_sink_init(struct sc_v4l2_sink *vs, const char *device_name,
+                  struct size frame_size);
+
+void
+sc_v4l2_sink_destroy(struct sc_v4l2_sink *vs);
+
+#endif

app/tests/test_control_msg_serialize.c

@@ -146,14 +146,18 @@ static void test_serialize_inject_scroll_event(void) {
 static void test_serialize_back_or_screen_on(void) {
     struct control_msg msg = {
         .type = CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON,
+        .back_or_screen_on = {
+            .action = AKEY_EVENT_ACTION_UP,
+        },
     };
 
     unsigned char buf[CONTROL_MSG_MAX_SIZE];
     size_t size = control_msg_serialize(&msg, buf);
-    assert(size == 1);
+    assert(size == 2);
 
     const unsigned char expected[] = {
         CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON,
+        0x01, // AKEY_EVENT_ACTION_UP
     };
     assert(!memcmp(buf, expected, sizeof(expected)));
 }

app/tests/test_strutil.c

@@ -287,6 +287,18 @@ static void test_parse_integer_with_suffix(void) {
     assert(!ok);
 }
 
+static void test_strlist_contains(void) {
+    assert(strlist_contains("a,bc,def", ',', "bc"));
+    assert(!strlist_contains("a,bc,def", ',', "b"));
+    assert(strlist_contains("", ',', ""));
+    assert(strlist_contains("abc,", ',', ""));
+    assert(strlist_contains(",abc", ',', ""));
+    assert(strlist_contains("abc,,def", ',', ""));
+    assert(!strlist_contains("abc", ',', ""));
+    assert(strlist_contains(",,|x", '|', ",,"));
+    assert(strlist_contains("xyz", '\0', "xyz"));
+}
+
 int main(int argc, char *argv[]) {
     (void) argc;
     (void) argv;
@@ -304,5 +316,6 @@ int main(int argc, char *argv[]) {
     test_parse_integer();
     test_parse_integers();
     test_parse_integer_with_suffix();
+    test_strlist_contains();
     return 0;
 }

server/src/main/java/com/genymobile/scrcpy/ControlMessage.java

@@ -71,6 +71,13 @@ public final class ControlMessage {
         return msg;
     }
 
+    public static ControlMessage createBackOrScreenOn(int action) {
+        ControlMessage msg = new ControlMessage();
+        msg.type = TYPE_BACK_OR_SCREEN_ON;
+        msg.action = action;
+        return msg;
+    }
+
     public static ControlMessage createSetClipboard(String text, boolean paste) {
         ControlMessage msg = new ControlMessage();
         msg.type = TYPE_SET_CLIPBOARD;

server/src/main/java/com/genymobile/scrcpy/ControlMessageReader.java

@@ -11,6 +11,7 @@ public class ControlMessageReader {
     static final int INJECT_KEYCODE_PAYLOAD_LENGTH = 13;
     static final int INJECT_TOUCH_EVENT_PAYLOAD_LENGTH = 27;
     static final int INJECT_SCROLL_EVENT_PAYLOAD_LENGTH = 20;
+    static final int BACK_OR_SCREEN_ON_LENGTH = 1;
     static final int SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH = 1;
     static final int SET_CLIPBOARD_FIXED_PAYLOAD_LENGTH = 1;
 
@@ -66,13 +67,15 @@ public class ControlMessageReader {
             case ControlMessage.TYPE_INJECT_SCROLL_EVENT:
                 msg = parseInjectScrollEvent();
                 break;
+            case ControlMessage.TYPE_BACK_OR_SCREEN_ON:
+                msg = parseBackOrScreenOnEvent();
+                break;
             case ControlMessage.TYPE_SET_CLIPBOARD:
                 msg = parseSetClipboard();
                 break;
             case ControlMessage.TYPE_SET_SCREEN_POWER_MODE:
                 msg = parseSetScreenPowerMode();
                 break;
-            case ControlMessage.TYPE_BACK_OR_SCREEN_ON:
             case ControlMessage.TYPE_EXPAND_NOTIFICATION_PANEL:
             case ControlMessage.TYPE_COLLAPSE_NOTIFICATION_PANEL:
             case ControlMessage.TYPE_GET_CLIPBOARD:
@@ -150,6 +153,14 @@ public class ControlMessageReader {
         return ControlMessage.createInjectScrollEvent(position, hScroll, vScroll);
     }
 
+    private ControlMessage parseBackOrScreenOnEvent() {
+        if (buffer.remaining() < BACK_OR_SCREEN_ON_LENGTH) {
+            return null;
+        }
+        int action = toUnsigned(buffer.get());
+        return ControlMessage.createBackOrScreenOn(action);
+    }
+
     private ControlMessage parseSetClipboard() {
         if (buffer.remaining() < SET_CLIPBOARD_FIXED_PAYLOAD_LENGTH) {
             return null;

server/src/main/java/com/genymobile/scrcpy/Controller.java

@@ -101,7 +101,7 @@ public class Controller {
                 break;
             case ControlMessage.TYPE_BACK_OR_SCREEN_ON:
                 if (device.supportsInputEvents()) {
-                    pressBackOrTurnScreenOn();
+                    pressBackOrTurnScreenOn(msg.getAction());
                 }
                 break;
             case ControlMessage.TYPE_EXPAND_NOTIFICATION_PANEL:
@@ -255,12 +255,22 @@ public class Controller {
         }, 200, TimeUnit.MILLISECONDS);
     }
 
-    private boolean pressBackOrTurnScreenOn() {
-        int keycode = Device.isScreenOn() ? KeyEvent.KEYCODE_BACK : KeyEvent.KEYCODE_POWER;
-        if (keepPowerModeOff && keycode == KeyEvent.KEYCODE_POWER) {
+    private boolean pressBackOrTurnScreenOn(int action) {
+        if (Device.isScreenOn()) {
+            return device.injectKeyEvent(action, KeyEvent.KEYCODE_BACK, 0, 0);
+        }
+
+        // Screen is off
+        // Only press POWER on ACTION_DOWN
+        if (action != KeyEvent.ACTION_DOWN) {
+            // do nothing,
+            return true;
+        }
+
+        if (keepPowerModeOff) {
             schedulePowerModeOff();
         }
-        return device.injectKeycode(keycode);
+        return device.injectKeycode(KeyEvent.KEYCODE_POWER);
     }
 
     private boolean setClipboard(String text, boolean paste) {

server/src/main/java/com/genymobile/scrcpy/Device.java

@@ -25,6 +25,9 @@ public final class Device {
     public static final int POWER_MODE_OFF = SurfaceControl.POWER_MODE_OFF;
     public static final int POWER_MODE_NORMAL = SurfaceControl.POWER_MODE_NORMAL;
 
+    public static final int LOCK_VIDEO_ORIENTATION_UNLOCKED = -1;
+    public static final int LOCK_VIDEO_ORIENTATION_INITIAL = -2;
+
     private static final ServiceManager SERVICE_MANAGER = new ServiceManager();
 
     public interface RotationListener {

server/src/main/java/com/genymobile/scrcpy/ScreenInfo.java

@@ -82,6 +82,12 @@ public final class ScreenInfo {
 
     public static ScreenInfo computeScreenInfo(DisplayInfo displayInfo, Rect crop, int maxSize, int lockedVideoOrientation) {
         int rotation = displayInfo.getRotation();
+
+        if (lockedVideoOrientation == Device.LOCK_VIDEO_ORIENTATION_INITIAL) {
+            // The user requested to lock the video orientation to the current orientation
+            lockedVideoOrientation = rotation;
+        }
+
         Size deviceSize = displayInfo.getSize();
         Rect contentRect = new Rect(0, 0, deviceSize.getWidth(), deviceSize.getHeight());
         if (crop != null) {

server/src/test/java/com/genymobile/scrcpy/ControlMessageReaderTest.java

@@ -154,6 +154,7 @@ public class ControlMessageReaderTest {
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         DataOutputStream dos = new DataOutputStream(bos);
         dos.writeByte(ControlMessage.TYPE_BACK_OR_SCREEN_ON);
+        dos.writeByte(KeyEvent.ACTION_UP);
 
         byte[] packet = bos.toByteArray();
 
@@ -161,6 +162,7 @@ public class ControlMessageReaderTest {
         ControlMessage event = reader.next();
 
         Assert.assertEquals(ControlMessage.TYPE_BACK_OR_SCREEN_ON, event.getType());
+        Assert.assertEquals(KeyEvent.ACTION_UP, event.getAction());
     }
 
     @Test