[FFmpeg-devel] [PATCH] x11grab: fixed next frame capture time calculation

[Trevor \\ Higgins]

The next frame time could slip, causing the frame rate to drop until
 frames were dropped. Now will capture at the next correct moment instead.
---
 libavdevice/x11grab.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/libavdevice/x11grab.c b/libavdevice/x11grab.c
index bdfaa66..029d490 100644
--- a/libavdevice/x11grab.c
+++ b/libavdevice/x11grab.c
@@ -526,23 +526,22 @@ static int x11grab_read_packet(AVFormatContext *s1, AVPacket *pkt)
     int64_t curtime, delay;
     struct timespec ts;
 
-    /* Calculate the time of the next frame */
-    s->time_frame += INT64_C(1000000);
-
     /* wait based on the frame rate */
     for (;;) {
         curtime = av_gettime();
         delay   = s->time_frame * av_q2d(s->time_base) - curtime;
-        if (delay <= 0) {
-            if (delay < INT64_C(-1000000) * av_q2d(s->time_base))
-                s->time_frame += INT64_C(1000000);
+        if (delay <= 0)
             break;
-        }
         ts.tv_sec  = delay / 1000000;
         ts.tv_nsec = (delay % 1000000) * 1000;
         nanosleep(&ts, NULL);
     }
 
+    /* Calculate the time of the next frame */
+    do{
+      s->time_frame += INT64_C(1000000);
+    }while((s->time_frame * av_q2d(s->time_base) - curtime) <= 0);
+
     av_init_packet(pkt);
     pkt->data = image->data;
     pkt->size = s->frame_size;
-- 
2.5.0