Extract sc_delay_buffer

A video buffer had 2 responsibilities:
 - handle the frame delaying mechanism (queuing packets and pushing them
   after the expected delay);
 - keep only the most recent frame (using a sc_frame_buffer).

In order to be able to reuse only the frame delaying mechanism, extract
it to a separate component, sc_delay_buffer.

app/meson.build

@@ -10,6 +10,7 @@ src = [
     'src/control_msg.c',
     'src/controller.c',
     'src/decoder.c',
+    'src/delay_buffer.c',
     'src/demuxer.c',
     'src/device_msg.c',
     'src/icon.c',

app/src/delay_buffer.c

@@ -0,0 +1,246 @@
+#include "delay_buffer.h"
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include <libavutil/avutil.h>
+#include <libavformat/avformat.h>
+
+#include "util/log.h"
+
+#define SC_BUFFERING_NDEBUG // comment to debug
+
+static bool
+sc_delayed_frame_init(struct sc_delayed_frame *dframe, const AVFrame *frame) {
+    dframe->frame = av_frame_alloc();
+    if (!dframe->frame) {
+        LOG_OOM();
+        return false;
+    }
+
+    if (av_frame_ref(dframe->frame, frame)) {
+        LOG_OOM();
+        av_frame_free(&dframe->frame);
+        return false;
+    }
+
+    return true;
+}
+
+static void
+sc_delayed_frame_destroy(struct sc_delayed_frame *dframe) {
+    av_frame_unref(dframe->frame);
+    av_frame_free(&dframe->frame);
+}
+
+static bool
+sc_delay_buffer_offer(struct sc_delay_buffer *db, const AVFrame *frame) {
+    return db->cbs->on_new_frame(db, frame, db->cbs_userdata);
+}
+
+static int
+run_buffering(void *data) {
+    struct sc_delay_buffer *db = data;
+
+    assert(db->delay > 0);
+
+    for (;;) {
+        sc_mutex_lock(&db->b.mutex);
+
+        while (!db->b.stopped && sc_vecdeque_is_empty(&db->b.queue)) {
+            sc_cond_wait(&db->b.queue_cond, &db->b.mutex);
+        }
+
+        if (db->b.stopped) {
+            sc_mutex_unlock(&db->b.mutex);
+            goto stopped;
+        }
+
+        struct sc_delayed_frame dframe = sc_vecdeque_pop(&db->b.queue);
+
+        sc_tick max_deadline = sc_tick_now() + db->delay;
+        // PTS (written by the server) are expressed in microseconds
+        sc_tick pts = SC_TICK_FROM_US(dframe.frame->pts);
+
+        bool timed_out = false;
+        while (!db->b.stopped && !timed_out) {
+            sc_tick deadline = sc_clock_to_system_time(&db->b.clock, pts)
+                             + db->delay;
+            if (deadline > max_deadline) {
+                deadline = max_deadline;
+            }
+
+            timed_out =
+                !sc_cond_timedwait(&db->b.wait_cond, &db->b.mutex, deadline);
+        }
+
+        bool stopped = db->b.stopped;
+        sc_mutex_unlock(&db->b.mutex);
+
+        if (stopped) {
+            sc_delayed_frame_destroy(&dframe);
+            goto stopped;
+        }
+
+#ifndef SC_BUFFERING_NDEBUG
+        LOGD("Buffering: %" PRItick ";%" PRItick ";%" PRItick,
+             pts, dframe.push_date, sc_tick_now());
+#endif
+
+        bool ok = sc_delay_buffer_offer(db, dframe.frame);
+        sc_delayed_frame_destroy(&dframe);
+        if (!ok) {
+            LOGE("Delayed frame could not be pushed, stopping");
+            sc_mutex_lock(&db->b.mutex);
+            // Prevent to push any new packet
+            db->b.stopped = true;
+            sc_mutex_unlock(&db->b.mutex);
+            goto stopped;
+        }
+    }
+
+stopped:
+    assert(db->b.stopped);
+
+    // Flush queue
+    while (!sc_vecdeque_is_empty(&db->b.queue)) {
+        struct sc_delayed_frame *dframe = sc_vecdeque_popref(&db->b.queue);
+        sc_delayed_frame_destroy(dframe);
+    }
+
+    LOGD("Buffering thread ended");
+
+    return 0;
+}
+
+bool
+sc_delay_buffer_init(struct sc_delay_buffer *db, sc_tick delay,
+                     const struct sc_delay_buffer_callbacks *cbs,
+                     void *cbs_userdata) {
+    assert(delay >= 0);
+
+    if (delay) {
+        bool ok = sc_mutex_init(&db->b.mutex);
+        if (!ok) {
+            return false;
+        }
+
+        ok = sc_cond_init(&db->b.queue_cond);
+        if (!ok) {
+            sc_mutex_destroy(&db->b.mutex);
+            return false;
+        }
+
+        ok = sc_cond_init(&db->b.wait_cond);
+        if (!ok) {
+            sc_cond_destroy(&db->b.queue_cond);
+            sc_mutex_destroy(&db->b.mutex);
+            return false;
+        }
+
+        sc_clock_init(&db->b.clock);
+        sc_vecdeque_init(&db->b.queue);
+    }
+
+    assert(cbs);
+    assert(cbs->on_new_frame);
+
+    db->delay = delay;
+    db->cbs = cbs;
+    db->cbs_userdata = cbs_userdata;
+
+    return true;
+}
+
+bool
+sc_delay_buffer_start(struct sc_delay_buffer *db) {
+    if (db->delay) {
+        bool ok =
+            sc_thread_create(&db->b.thread, run_buffering, "scrcpy-dbuf", db);
+        if (!ok) {
+            LOGE("Could not start buffering thread");
+            return false;
+        }
+    }
+
+    return true;
+}
+
+void
+sc_delay_buffer_stop(struct sc_delay_buffer *db) {
+    if (db->delay) {
+        sc_mutex_lock(&db->b.mutex);
+        db->b.stopped = true;
+        sc_cond_signal(&db->b.queue_cond);
+        sc_cond_signal(&db->b.wait_cond);
+        sc_mutex_unlock(&db->b.mutex);
+    }
+}
+
+void
+sc_delay_buffer_join(struct sc_delay_buffer *db) {
+    if (db->delay) {
+        sc_thread_join(&db->b.thread, NULL);
+    }
+}
+
+void
+sc_delay_buffer_destroy(struct sc_delay_buffer *db) {
+    if (db->delay) {
+        sc_cond_destroy(&db->b.wait_cond);
+        sc_cond_destroy(&db->b.queue_cond);
+        sc_mutex_destroy(&db->b.mutex);
+    }
+}
+
+bool
+sc_delay_buffer_push(struct sc_delay_buffer *db, const AVFrame *frame) {
+    if (!db->delay) {
+        // No buffering
+        return sc_delay_buffer_offer(db, frame);
+    }
+
+    sc_mutex_lock(&db->b.mutex);
+
+    if (db->b.stopped) {
+        sc_mutex_unlock(&db->b.mutex);
+        return false;
+    }
+
+    sc_tick pts = SC_TICK_FROM_US(frame->pts);
+    sc_clock_update(&db->b.clock, sc_tick_now(), pts);
+    sc_cond_signal(&db->b.wait_cond);
+
+    if (db->b.clock.count == 1) {
+        sc_mutex_unlock(&db->b.mutex);
+        // First frame, offer it immediately, for two reasons:
+        //  - not to delay the opening of the scrcpy window
+        //  - the buffering estimation needs at least two clock points, so it
+        //  could not handle the first frame
+        return sc_delay_buffer_offer(db, frame);
+    }
+
+    struct sc_delayed_frame dframe;
+    bool ok = sc_delayed_frame_init(&dframe, frame);
+    if (!ok) {
+        sc_mutex_unlock(&db->b.mutex);
+        return false;
+    }
+
+#ifndef SC_BUFFERING_NDEBUG
+    dframe.push_date = sc_tick_now();
+#endif
+
+    ok = sc_vecdeque_push(&db->b.queue, dframe);
+    if (!ok) {
+        sc_mutex_unlock(&db->b.mutex);
+        LOG_OOM();
+        return false;
+    }
+
+    sc_cond_signal(&db->b.queue_cond);
+
+    sc_mutex_unlock(&db->b.mutex);
+
+    return true;
+}

app/src/delay_buffer.h

@@ -0,0 +1,69 @@
+#ifndef SC_DELAY_BUFFER_H
+#define SC_DELAY_BUFFER_H
+
+#include "common.h"
+
+#include <stdbool.h>
+
+#include "clock.h"
+#include "util/thread.h"
+#include "util/tick.h"
+#include "util/vecdeque.h"
+
+// forward declarations
+typedef struct AVFrame AVFrame;
+
+struct sc_delayed_frame {
+    AVFrame *frame;
+#ifndef NDEBUG
+    sc_tick push_date;
+#endif
+};
+
+struct sc_delayed_frame_queue SC_VECDEQUE(struct sc_delayed_frame);
+
+struct sc_delay_buffer {
+    sc_tick delay;
+
+    // only if delay > 0
+    struct {
+        sc_thread thread;
+        sc_mutex mutex;
+        sc_cond queue_cond;
+        sc_cond wait_cond;
+
+        struct sc_clock clock;
+        struct sc_delayed_frame_queue queue;
+        bool stopped;
+    } b; // buffering
+
+    const struct sc_delay_buffer_callbacks *cbs;
+    void *cbs_userdata;
+};
+
+struct sc_delay_buffer_callbacks {
+    bool (*on_new_frame)(struct sc_delay_buffer *db, const AVFrame *frame,
+                         void *userdata);
+};
+
+bool
+sc_delay_buffer_init(struct sc_delay_buffer *db, sc_tick delay,
+                     const struct sc_delay_buffer_callbacks *cbs,
+                     void *cbs_userdata);
+
+bool
+sc_delay_buffer_start(struct sc_delay_buffer *db);
+
+void
+sc_delay_buffer_stop(struct sc_delay_buffer *db);
+
+void
+sc_delay_buffer_join(struct sc_delay_buffer *db);
+
+void
+sc_delay_buffer_destroy(struct sc_delay_buffer *db);
+
+bool
+sc_delay_buffer_push(struct sc_delay_buffer *db, const AVFrame *frame);
+
+#endif

app/src/video_buffer.c

@@ -8,32 +8,13 @@
 
 #include "util/log.h"
 
-#define SC_BUFFERING_NDEBUG // comment to debug
-
 static bool
-sc_video_buffer_frame_init(struct sc_video_buffer_frame *vb_frame,
+sc_delay_buffer_on_new_frame(struct sc_delay_buffer *db, const AVFrame *frame,
-                           const AVFrame *frame) {
+                             void *userdata) {
-    vb_frame->frame = av_frame_alloc();
+    (void) db;
-    if (!vb_frame->frame) {
-        return false;
-    }
 
-    if (av_frame_ref(vb_frame->frame, frame)) {
+    struct sc_video_buffer *vb = userdata;
-        av_frame_free(&vb_frame->frame);
-        return false;
-    }
 
-    return true;
-}
-
-static void
-sc_video_buffer_frame_destroy(struct sc_video_buffer_frame *vb_frame) {
-    av_frame_unref(vb_frame->frame);
-    av_frame_free(&vb_frame->frame);
-}
-
-static bool
-sc_video_buffer_offer(struct sc_video_buffer *vb, const AVFrame *frame) {
     bool previous_skipped;
     bool ok = sc_frame_buffer_push(&vb->fb, frame, &previous_skipped);
     if (!ok) {
@@ -43,83 +24,8 @@ sc_video_buffer_offer(struct sc_video_buffer *vb, const AVFrame *frame) {
     return vb->cbs->on_new_frame(vb, previous_skipped, vb->cbs_userdata);
 }
 
-static int
-run_buffering(void *data) {
-    struct sc_video_buffer *vb = data;
-
-    assert(vb->buffering_time > 0);
-
-    for (;;) {
-        sc_mutex_lock(&vb->b.mutex);
-
-        while (!vb->b.stopped && sc_vecdeque_is_empty(&vb->b.queue)) {
-            sc_cond_wait(&vb->b.queue_cond, &vb->b.mutex);
-        }
-
-        if (vb->b.stopped) {
-            sc_mutex_unlock(&vb->b.mutex);
-            goto stopped;
-        }
-
-        struct sc_video_buffer_frame vb_frame = sc_vecdeque_pop(&vb->b.queue);
-
-        sc_tick max_deadline = sc_tick_now() + vb->buffering_time;
-        // PTS (written by the server) are expressed in microseconds
-        sc_tick pts = SC_TICK_FROM_US(vb_frame.frame->pts);
-
-        bool timed_out = false;
-        while (!vb->b.stopped && !timed_out) {
-            sc_tick deadline = sc_clock_to_system_time(&vb->b.clock, pts)
-                             + vb->buffering_time;
-            if (deadline > max_deadline) {
-                deadline = max_deadline;
-            }
-
-            timed_out =
-                !sc_cond_timedwait(&vb->b.wait_cond, &vb->b.mutex, deadline);
-        }
-
-        if (vb->b.stopped) {
-            sc_video_buffer_frame_destroy(&vb_frame);
-            sc_mutex_unlock(&vb->b.mutex);
-            goto stopped;
-        }
-
-        sc_mutex_unlock(&vb->b.mutex);
-
-#ifndef SC_BUFFERING_NDEBUG
-        LOGD("Buffering: %" PRItick ";%" PRItick ";%" PRItick,
-             pts, vb_frame.push_date, sc_tick_now());
-#endif
-
-        bool ok = sc_video_buffer_offer(vb, vb_frame.frame);
-        sc_video_buffer_frame_destroy(&vb_frame);
-        if (!ok) {
-            LOGE("Delayed frame could not be pushed, stopping");
-            sc_mutex_lock(&vb->b.mutex);
-            // Prevent to push any new packet
-            vb->b.stopped = true;
-            sc_mutex_unlock(&vb->b.mutex);
-            goto stopped;
-        }
-    }
-
-stopped:
-    assert(vb->b.stopped);
-
-    // Flush queue
-    while (!sc_vecdeque_is_empty(&vb->b.queue)) {
-        struct sc_video_buffer_frame *p = sc_vecdeque_popref(&vb->b.queue);
-        sc_video_buffer_frame_destroy(p);
-    }
-
-    LOGD("Buffering thread ended");
-
-    return 0;
-}
-
 bool
-sc_video_buffer_init(struct sc_video_buffer *vb, sc_tick buffering_time,
+sc_video_buffer_init(struct sc_video_buffer *vb, sc_tick delay,
                      const struct sc_video_buffer_callbacks *cbs,
                      void *cbs_userdata) {
     bool ok = sc_frame_buffer_init(&vb->fb);
@@ -127,135 +33,49 @@ sc_video_buffer_init(struct sc_video_buffer *vb, sc_tick buffering_time,
         return false;
     }
 
-    assert(buffering_time >= 0);
+    static const struct sc_delay_buffer_callbacks db_cbs = {
-    if (buffering_time) {
+        .on_new_frame = sc_delay_buffer_on_new_frame,
-        ok = sc_mutex_init(&vb->b.mutex);
+    };
+
+    ok = sc_delay_buffer_init(&vb->db, delay, &db_cbs, vb);
     if (!ok) {
         sc_frame_buffer_destroy(&vb->fb);
         return false;
     }
 
-        ok = sc_cond_init(&vb->b.queue_cond);
-        if (!ok) {
-            sc_mutex_destroy(&vb->b.mutex);
-            sc_frame_buffer_destroy(&vb->fb);
-            return false;
-        }
-
-        ok = sc_cond_init(&vb->b.wait_cond);
-        if (!ok) {
-            sc_cond_destroy(&vb->b.queue_cond);
-            sc_mutex_destroy(&vb->b.mutex);
-            sc_frame_buffer_destroy(&vb->fb);
-            return false;
-        }
-
-        sc_clock_init(&vb->b.clock);
-        sc_vecdeque_init(&vb->b.queue);
-    }
-
     assert(cbs);
     assert(cbs->on_new_frame);
 
-    vb->buffering_time = buffering_time;
     vb->cbs = cbs;
     vb->cbs_userdata = cbs_userdata;
+
     return true;
 }
 
 bool
 sc_video_buffer_start(struct sc_video_buffer *vb) {
-    if (vb->buffering_time) {
+    return sc_delay_buffer_start(&vb->db);
-        bool ok =
-            sc_thread_create(&vb->b.thread, run_buffering, "scrcpy-vbuf", vb);
-        if (!ok) {
-            LOGE("Could not start buffering thread");
-            return false;
-        }
-    }
-
-    return true;
 }
 
 void
 sc_video_buffer_stop(struct sc_video_buffer *vb) {
-    if (vb->buffering_time) {
+    return sc_delay_buffer_stop(&vb->db);
-        sc_mutex_lock(&vb->b.mutex);
-        vb->b.stopped = true;
-        sc_cond_signal(&vb->b.queue_cond);
-        sc_cond_signal(&vb->b.wait_cond);
-        sc_mutex_unlock(&vb->b.mutex);
-    }
 }
 
 void
 sc_video_buffer_join(struct sc_video_buffer *vb) {
-    if (vb->buffering_time) {
+    return sc_delay_buffer_join(&vb->db);
-        sc_thread_join(&vb->b.thread, NULL);
-    }
 }
 
 void
 sc_video_buffer_destroy(struct sc_video_buffer *vb) {
     sc_frame_buffer_destroy(&vb->fb);
-    if (vb->buffering_time) {
+    sc_delay_buffer_destroy(&vb->db);
-        sc_cond_destroy(&vb->b.wait_cond);
-        sc_cond_destroy(&vb->b.queue_cond);
-        sc_mutex_destroy(&vb->b.mutex);
-    }
 }
 
 bool
 sc_video_buffer_push(struct sc_video_buffer *vb, const AVFrame *frame) {
-    if (!vb->buffering_time) {
+    return sc_delay_buffer_push(&vb->db, frame);
-        // No buffering
-        return sc_video_buffer_offer(vb, frame);
-    }
-
-    sc_mutex_lock(&vb->b.mutex);
-
-    if (vb->b.stopped) {
-        sc_mutex_unlock(&vb->b.mutex);
-        return false;
-    }
-
-    sc_tick pts = SC_TICK_FROM_US(frame->pts);
-    sc_clock_update(&vb->b.clock, sc_tick_now(), pts);
-    sc_cond_signal(&vb->b.wait_cond);
-
-    if (vb->b.clock.count == 1) {
-        sc_mutex_unlock(&vb->b.mutex);
-        // First frame, offer it immediately, for two reasons:
-        //  - not to delay the opening of the scrcpy window
-        //  - the buffering estimation needs at least two clock points, so it
-        //  could not handle the first frame
-        return sc_video_buffer_offer(vb, frame);
-    }
-
-    struct sc_video_buffer_frame vb_frame;
-    bool ok = sc_video_buffer_frame_init(&vb_frame, frame);
-    if (!ok) {
-        sc_mutex_unlock(&vb->b.mutex);
-        LOG_OOM();
-        return false;
-    }
-
-#ifndef SC_BUFFERING_NDEBUG
-    vb_frame.push_date = sc_tick_now();
-#endif
-
-    ok = sc_vecdeque_push(&vb->b.queue, vb_frame);
-    if (!ok) {
-        sc_mutex_unlock(&vb->b.mutex);
-        LOG_OOM();
-        return false;
-    }
-
-    sc_cond_signal(&vb->b.queue_cond);
-
-    sc_mutex_unlock(&vb->b.mutex);
-
-    return true;
 }
 
 void

app/src/video_buffer.h

@@ -5,41 +5,13 @@
 
 #include <stdbool.h>
 
-#include "clock.h"
+#include "delay_buffer.h"
 #include "frame_buffer.h"
-#include "util/thread.h"
-#include "util/tick.h"
-#include "util/vecdeque.h"
-
-// forward declarations
-typedef struct AVFrame AVFrame;
-
-struct sc_video_buffer_frame {
-    AVFrame *frame;
-#ifndef NDEBUG
-    sc_tick push_date;
-#endif
-};
-
-struct sc_video_buffer_frame_queue SC_VECDEQUE(struct sc_video_buffer_frame);
 
 struct sc_video_buffer {
+    struct sc_delay_buffer db;
     struct sc_frame_buffer fb;
 
-    sc_tick buffering_time;
-
-    // only if buffering_time > 0
-    struct {
-        sc_thread thread;
-        sc_mutex mutex;
-        sc_cond queue_cond;
-        sc_cond wait_cond;
-
-        struct sc_clock clock;
-        struct sc_video_buffer_frame_queue queue;
-        bool stopped;
-    } b; // buffering
-
     const struct sc_video_buffer_callbacks *cbs;
     void *cbs_userdata;
 };
@@ -50,7 +22,7 @@ struct sc_video_buffer_callbacks {
 };
 
 bool
-sc_video_buffer_init(struct sc_video_buffer *vb, sc_tick buffering_time,
+sc_video_buffer_init(struct sc_video_buffer *vb, sc_tick delay,
                      const struct sc_video_buffer_callbacks *cbs,
                      void *cbs_userdata);