lavf: Use av_gettime_relative()

Whenever av_gettime() is used to measure relative period of time,
av_gettime_relative() is prefered as it guarantee monotonic time
on supported platforms.
Signed-off-by: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/avio.c

@@ -312,8 +312,8 @@ static inline int retry_transfer_wrapper(URLContext *h, uint8_t *buf,
             } else {
                 if (h->rw_timeout) {
                     if (!wait_since)
-                        wait_since = av_gettime();
-                    else if (av_gettime() > wait_since + h->rw_timeout)
+                        wait_since = av_gettime_relative();
+                    else if (av_gettime_relative() > wait_since + h->rw_timeout)
                         return AVERROR(EIO);
                 }
                 av_usleep(1000);

libavformat/network.c

@@ -163,8 +163,8 @@ int ff_network_wait_fd_timeout(int fd, int write, int64_t timeout, AVIOInterrupt
             return ret;
         if (timeout > 0) {
             if (!wait_start)
-                wait_start = av_gettime();
-            else if (av_gettime() - wait_start > timeout)
+                wait_start = av_gettime_relative();
+            else if (av_gettime_relative() - wait_start > timeout)
                 return AVERROR(ETIMEDOUT);
         }
     }

libavformat/sapenc.c

@@ -245,7 +245,7 @@ static int sap_write_packet(AVFormatContext *s, AVPacket *pkt)
 {
     AVFormatContext *rtpctx;
     struct SAPState *sap = s->priv_data;
-    int64_t now = av_gettime();
+    int64_t now = av_gettime_relative();
 
     if (!sap->last_time || now - sap->last_time > 5000000) {
         int ret = ffurl_write(sap->ann_fd, sap->ann, sap->ann_size);