Add buffering command line options

Add --display-buffer and --v4l2-buffer options to configure buffering
time.

README.md

@@ -321,6 +321,24 @@ For example, you could capture the video within [OBS].
 [OBS]: https://obsproject.com/fr
 
 
+#### Buffering
+
+It is possible to add buffering. This increases latency but reduces jitter (see
+#2464).
+
+The option is available for display buffering:
+
+```bash
+scrcpy --display-buffer=50  # add 50 ms buffering for display
+```
+
+and V4L2 sink:
+
+```bash
+scrcpy --v4l2-buffer=500    # add 500 ms buffering for v4l2 sink
+```
+
+
 ### Connection
 
 #### Wireless

app/scrcpy.1

@@ -56,6 +56,12 @@ The list of possible display ids can be listed by "adb shell dumpsys display"
 
 Default is 0.
 
+.TP
+.BI "\-\-display\-buffer ms
+Add a buffering delay (in milliseconds) before displaying. This increases latency to compensate for jitter.
+
+Default is 0 (no buffering).
+
 .TP
 .BI "\-\-encoder " name
 Use a specific MediaCodec encoder (must be a H.264 encoder).
@@ -191,6 +197,14 @@ Output to v4l2loopback device.
 
 It requires to lock the video orientation (see \fB\-\-lock\-video\-orientation\fR).
 
+.TP
+.BI "\-\-v4l2-buffer " ms
+Add a buffering delay (in milliseconds) before pushing frames. This increases latency to compensate for jitter.
+
+This option is similar to \fB\-\-display\-buffer\fR, but specific to V4L2 sink.
+
+Default is 0 (no buffering).
+
 .TP
 .BI "\-V, \-\-verbosity " value
 Set the log level ("verbose", "debug", "info", "warn" or "error").

app/src/cli.c

@@ -55,6 +55,12 @@ scrcpy_print_usage(const char *arg0) {
         "\n"
         "        Default is 0.\n"
         "\n"
+        "    --display-buffer ms\n"
+        "        Add a buffering delay (in milliseconds) before displaying.\n"
+        "        This increases latency to compensate for jitter.\n"
+        "\n"
+        "        Default is 0 (no buffering).\n"
+        "\n"
         "    --encoder name\n"
         "        Use a specific MediaCodec encoder (must be a H.264 encoder).\n"
         "\n"
@@ -182,6 +188,15 @@ scrcpy_print_usage(const char *arg0) {
         "        It requires to lock the video orientation (see\n"
         "        --lock-video-orientation).\n"
         "\n"
+        "    --v4l2-buffer ms\n"
+        "        Add a buffering delay (in milliseconds) before pushing\n"
+        "        frames. This increases latency to compensate for jitter.\n"
+        "\n"
+        "        This option is similar to --display-buffer, but specific to\n"
+        "        V4L2 sink.\n"
+        "\n"
+        "        Default is 0 (no buffering).\n"
+        "\n"
 #endif
         "    -V, --verbosity value\n"
         "        Set the log level (verbose, debug, info, warn or error).\n"
@@ -392,6 +407,19 @@ parse_max_fps(const char *s, uint16_t *max_fps) {
     return true;
 }
 
+static bool
+parse_buffering_time(const char *s, sc_tick *tick) {
+    long value;
+    bool ok = parse_integer_arg(s, &value, false, 0, 0x7FFFFFFF,
+                                "buffering time");
+    if (!ok) {
+        return false;
+    }
+
+    *tick = SC_TICK_FROM_MS(value);
+    return true;
+}
+
 static bool
 parse_lock_video_orientation(const char *s,
                              enum sc_lock_video_orientation *lock_mode) {
@@ -689,6 +717,8 @@ guess_record_format(const char *filename) {
 #define OPT_ENCODER_NAME           1025
 #define OPT_POWER_OFF_ON_CLOSE     1026
 #define OPT_V4L2_SINK              1027
+#define OPT_DISPLAY_BUFFER         1028
+#define OPT_V4L2_BUFFER            1029
 
 bool
 scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
@@ -700,6 +730,7 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
         {"disable-screensaver",    no_argument,       NULL,
                                                   OPT_DISABLE_SCREENSAVER},
         {"display",                required_argument, NULL, OPT_DISPLAY_ID},
+        {"display-buffer",         required_argument, NULL, OPT_DISPLAY_BUFFER},
         {"encoder",                required_argument, NULL, OPT_ENCODER_NAME},
         {"force-adb-forward",      no_argument,       NULL,
                                                   OPT_FORCE_ADB_FORWARD},
@@ -732,6 +763,7 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
         {"turn-screen-off",        no_argument,       NULL, 'S'},
 #ifdef HAVE_V4L2
         {"v4l2-sink",              required_argument, NULL, OPT_V4L2_SINK},
+        {"v4l2-buffer",            required_argument, NULL, OPT_V4L2_BUFFER},
 #endif
         {"verbosity",              required_argument, NULL, 'V'},
         {"version",                no_argument,       NULL, 'v'},
@@ -917,10 +949,20 @@ 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;
+            case OPT_DISPLAY_BUFFER:
+                if (!parse_buffering_time(optarg, &opts->display_buffer)) {
+                    return false;
+                }
+                break;
 #ifdef HAVE_V4L2
             case OPT_V4L2_SINK:
                 opts->v4l2_device = optarg;
                 break;
+            case OPT_V4L2_BUFFER:
+                if (!parse_buffering_time(optarg, &opts->v4l2_buffer)) {
+                    return false;
+                }
+                break;
 #endif
             default:
                 // getopt prints the error message on stderr
@@ -941,6 +983,11 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
              "See --lock-video-orientation.");
         opts->lock_video_orientation = SC_LOCK_VIDEO_ORIENTATION_INITIAL;
     }
+
+    if (opts->v4l2_buffer && !opts->v4l2_device) {
+        LOGE("V4L2 buffer value without V4L2 sink\n");
+        return false;
+    }
 #else
     if (!opts->display && !opts->record_filename) {
         LOGE("-N/--no-display requires screen recording (-r/--record)");

app/src/scrcpy.c

@@ -381,6 +381,7 @@ scrcpy(const struct scrcpy_options *options) {
             .rotation = options->rotation,
             .mipmaps = options->mipmaps,
             .fullscreen = options->fullscreen,
+            .buffering_time = options->display_buffer,
         };
 
         if (!screen_init(&s->screen, &screen_params)) {
@@ -393,7 +394,8 @@ scrcpy(const struct scrcpy_options *options) {
 
 #ifdef HAVE_V4L2
     if (options->v4l2_device) {
-        if (!sc_v4l2_sink_init(&s->v4l2_sink, options->v4l2_device, frame_size)) {
+        if (!sc_v4l2_sink_init(&s->v4l2_sink, options->v4l2_device, frame_size,
+                               options->v4l2_buffer)) {
             goto end;
         }
 

app/src/scrcpy.h

@@ -7,6 +7,8 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include "util/tick.h"
+
 enum sc_log_level {
     SC_LOG_LEVEL_VERBOSE,
     SC_LOG_LEVEL_DEBUG,
@@ -78,6 +80,8 @@ struct scrcpy_options {
     uint16_t window_width;
     uint16_t window_height;
     uint32_t display_id;
+    sc_tick display_buffer;
+    sc_tick v4l2_buffer;
     bool show_touches;
     bool fullscreen;
     bool always_on_top;
@@ -126,6 +130,8 @@ struct scrcpy_options {
     .window_width = 0, \
     .window_height = 0, \
     .display_id = 0, \
+    .display_buffer = 0, \
+    .v4l2_buffer = 0, \
     .show_touches = false, \
     .fullscreen = false, \
     .always_on_top = false, \

app/src/screen.c

@@ -308,7 +308,8 @@ screen_init(struct screen *screen, const struct screen_params *params) {
         .on_new_frame = sc_video_buffer_on_new_frame,
     };
 
-    bool ok = sc_video_buffer_init(&screen->vb, 0, &cbs, screen);
+    bool ok = sc_video_buffer_init(&screen->vb, params->buffering_time, &cbs,
+                                   screen);
     if (!ok) {
         LOGE("Could not initialize video buffer");
         return false;

app/src/screen.h

@@ -63,6 +63,8 @@ struct screen_params {
     bool mipmaps;
 
     bool fullscreen;
+
+    sc_tick buffering_time;
 };
 
 // initialize screen, create window, renderer and texture (window is hidden)

app/src/v4l2_sink.c

@@ -159,7 +159,7 @@ sc_v4l2_sink_open(struct sc_v4l2_sink *vs) {
         .on_new_frame = sc_video_buffer_on_new_frame,
     };
 
-    bool ok = sc_video_buffer_init(&vs->vb, 0, &cbs, vs);
+    bool ok = sc_video_buffer_init(&vs->vb, vs->buffering_time, &cbs, vs);
     if (!ok) {
         LOGE("Could not initialize video buffer");
         return false;
@@ -356,7 +356,7 @@ sc_v4l2_frame_sink_push(struct sc_frame_sink *sink, const AVFrame *frame) {
 
 bool
 sc_v4l2_sink_init(struct sc_v4l2_sink *vs, const char *device_name,
-                  struct size frame_size) {
+                  struct size frame_size, sc_tick buffering_time) {
     vs->device_name = strdup(device_name);
     if (!vs->device_name) {
         LOGE("Could not strdup v4l2 device name");
@@ -364,6 +364,7 @@ sc_v4l2_sink_init(struct sc_v4l2_sink *vs, const char *device_name,
     }
 
     vs->frame_size = frame_size;
+    vs->buffering_time = buffering_time;
 
     static const struct sc_frame_sink_ops ops = {
         .open = sc_v4l2_frame_sink_open,

app/src/v4l2_sink.h

@@ -6,6 +6,7 @@
 #include "coords.h"
 #include "trait/frame_sink.h"
 #include "video_buffer.h"
+#include "util/tick.h"
 
 #include <libavformat/avformat.h>
 
@@ -18,6 +19,7 @@ struct sc_v4l2_sink {
 
     char *device_name;
     struct size frame_size;
+    sc_tick buffering_time;
 
     sc_thread thread;
     sc_mutex mutex;
@@ -32,7 +34,7 @@ struct sc_v4l2_sink {
 
 bool
 sc_v4l2_sink_init(struct sc_v4l2_sink *vs, const char *device_name,
-                  struct size frame_size);
+                  struct size frame_size, sc_tick buffering_time);
 
 void
 sc_v4l2_sink_destroy(struct sc_v4l2_sink *vs);