ffmpeg: use av_rescale_delta() on the audio filter input

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

ffmpeg.h

@@ -217,6 +217,9 @@ typedef struct InputStream {
     int64_t       next_pts;  ///< synthetic pts for the next decode frame (in AV_TIME_BASE units)
     int64_t       pts;       ///< current pts of the decoded frame  (in AV_TIME_BASE units)
     int           wrap_correction_done;
+
+    int64_t filter_in_rescale_delta_last;
+
     double ts_scale;
     int is_start;            /* is 1 at the start and after a discontinuity */
     int saw_first_ts;