swr: check return value of swr_inject_silence/drop_output.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libswresample/swresample.c

@@ -762,8 +762,12 @@ int64_t swr_next_pts(struct SwrContext *s, int64_t pts){
 
         if(fabs(fdelta) > s->min_compensation) {
             if(!s->outpts || fabs(fdelta) > s->min_hard_compensation){
-                if(delta > 0) swr_inject_silence(s,  delta / s->out_sample_rate);
-                else          swr_drop_output   (s, -delta / s-> in_sample_rate);
+                int ret;
+                if(delta > 0) ret = swr_inject_silence(s,  delta / s->out_sample_rate);
+                else          ret = swr_drop_output   (s, -delta / s-> in_sample_rate);
+                if(ret<0){
+                    av_log(s, AV_LOG_ERROR, "Failed to compensate for timestamp delta of %f\n", fdelta);
+                }
             } else if(s->soft_compensation_duration && s->max_soft_compensation) {
                 int duration = s->out_sample_rate * s->soft_compensation_duration;
                 int comp = av_clipf(fdelta, -s->max_soft_compensation, s->max_soft_compensation) * duration ;