vaapi-recorder: Encode frames in a separate thread

Previously, vaapi_recorder_frame() would wait until the encoded
contents for a frame is written to the output file descriptor. This
delayed the repainting of the next frame, and affected frame rate
when capturing with high resolutions. Instead, wait only if there is
and attempted to encode two frames at the same time.

Increases framerate from 30 to 60 fps when capturing at 1920x1200 on
my SandryBridge system, although there are periodic slowdowns due to
disk writes.

src/compositor-drm.c

@@ -2471,8 +2471,6 @@ recorder_frame_notify(struct wl_listener *listener, void *data)
 	}
 
 	vaapi_recorder_frame(output->recorder, fd, output->current->stride / 4);
-
-	close(fd);
 }
 
 static void *

src/vaapi-recorder.c

@@ -47,11 +47,13 @@
 #include <stdint.h>
 #include <string.h>
 #include <unistd.h>
+#include <assert.h>
 
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 
+#include <pthread.h>
 
 #include <va/va.h>
 #include <va/va_drm.h>
@@ -89,6 +91,16 @@ struct vaapi_recorder {
 	int width, height;
 	int frame_count;
 
+	int destroying;
+	pthread_t worker_thread;
+	pthread_mutex_t mutex;
+	pthread_cond_t input_cond;
+
+	struct {
+		int valid;
+		int prime_fd, stride;
+	} input;
+
 	VADisplay va_dpy;
 
 	/* video post processing is used for colorspace conversion */
@@ -116,6 +128,9 @@ struct vaapi_recorder {
 	} encoder;
 };
 
+static void *
+worker_thread_function(void *);
+
 /* bistream code used for writing the packed headers */
 
 #define BITSTREAM_ALLOCATE_STEPPING	 4096
@@ -886,6 +901,33 @@ vpp_destroy(struct vaapi_recorder *r)
 	vaDestroyConfig(r->va_dpy, r->vpp.cfg);
 }
 
+static int
+setup_worker_thread(struct vaapi_recorder *r)
+{
+	pthread_mutex_init(&r->mutex, NULL);
+	pthread_cond_init(&r->input_cond, NULL);
+	pthread_create(&r->worker_thread, NULL, worker_thread_function, r);
+
+	return 1;
+}
+
+static void
+destroy_worker_thread(struct vaapi_recorder *r)
+{
+	pthread_mutex_lock(&r->mutex);
+
+	/* Make sure the worker thread finishes */
+	r->destroying = 1;
+	pthread_cond_signal(&r->input_cond);
+
+	pthread_mutex_unlock(&r->mutex);
+
+	pthread_join(r->worker_thread, NULL);
+
+	pthread_mutex_destroy(&r->mutex);
+	pthread_cond_destroy(&r->input_cond);
+}
+
 struct vaapi_recorder *
 vaapi_recorder_create(int drm_fd, int width, int height, const char *filename)
 {
@@ -904,9 +946,12 @@ vaapi_recorder_create(int drm_fd, int width, int height, const char *filename)
 	flags = O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC;
 	r->output_fd = open(filename, flags, 0644);
 
-	if (r->output_fd < 0)
+	if (setup_worker_thread(r) < 0)
 		goto err_free;
 
+	if (r->output_fd < 0)
+		goto err_thread;
+
 	r->va_dpy = vaGetDisplayDRM(drm_fd);
 	if (!r->va_dpy) {
 		weston_log("failed to create VA display\n");
@@ -936,6 +981,8 @@ err_va_dpy:
 	vaTerminate(r->va_dpy);
 err_fd:
 	close(r->output_fd);
+err_thread:
+	destroy_worker_thread(r);
 err_free:
 	free(r);
 
@@ -945,6 +992,8 @@ err_free:
 void
 vaapi_recorder_destroy(struct vaapi_recorder *r)
 {
+	destroy_worker_thread(r);
+
 	encoder_destroy(r);
 	vpp_destroy(r);
 
@@ -1033,20 +1082,22 @@ convert_rgb_to_yuv(struct vaapi_recorder *r, VASurfaceID rgb_surface)
 	return status;
 }
 
-void
-vaapi_recorder_frame(struct vaapi_recorder *r, int prime_fd,
-		     int stride)
+static void
+recorder_frame(struct vaapi_recorder *r)
 {
 	VASurfaceID rgb_surface;
 	VAStatus status;
 
-	status = create_surface_from_fd(r, prime_fd, stride, &rgb_surface);
+	status = create_surface_from_fd(r, r->input.prime_fd,
+					r->input.stride, &rgb_surface);
 	if (status != VA_STATUS_SUCCESS) {
 		weston_log("[libva recorder] "
 			   "failed to create surface from bo\n");
 		return;
 	}
 
+	close(r->input.prime_fd);
+
 	status = convert_rgb_to_yuv(r, rgb_surface);
 	if (status != VA_STATUS_SUCCESS) {
 		weston_log("[libva recorder] "
@@ -1059,4 +1110,44 @@ vaapi_recorder_frame(struct vaapi_recorder *r, int prime_fd,
 	vaDestroySurfaces(r->va_dpy, &rgb_surface, 1);
 }
 
+static void *
+worker_thread_function(void *data)
+{
+	struct vaapi_recorder *r = data;
+
+	pthread_mutex_lock(&r->mutex);
+
+	while (!r->destroying) {
+		if (!r->input.valid)
+			pthread_cond_wait(&r->input_cond, &r->mutex);
+
+		/* If the thread is awaken by destroy_worker_thread(),
+		 * there might not be valid input */
+		if (!r->input.valid)
+			continue;
+
+		recorder_frame(r);
+		r->input.valid = 0;
+	}
+
+	pthread_mutex_unlock(&r->mutex);
+
+	return NULL;
+}
+
+void
+vaapi_recorder_frame(struct vaapi_recorder *r, int prime_fd, int stride)
+{
+	pthread_mutex_lock(&r->mutex);
+
+	/* The mutex is never released while encoding, so this point should
+	 * never be reached if input.valid is true. */
+	assert(!r->input.valid);
 
+	r->input.prime_fd = prime_fd;
+	r->input.stride = stride;
+	r->input.valid = 1;
+	pthread_cond_signal(&r->input_cond);
+
+	pthread_mutex_unlock(&r->mutex);
+}