lavc: add a convenience function for rescaling timestamps in a packet

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:     2013-12-xx
 
 API changes, most recent first:
 
+2014-06-xx - xxxxxxx - lavc 55.55.0 - avcodec.h
+  Add av_packet_rescale_ts() to simplify timestamp conversion.
+
 2014-xx-xx - xxxxxxx - lavf 55.20.0 - avformat.h
   The proper way for providing a hint about the desired timebase to the muxers
   is now setting AVStream.time_base, instead of AVStream.codec.time_base as was

libavcodec/avcodec.h

@@ -3420,6 +3420,19 @@ void av_packet_move_ref(AVPacket *dst, AVPacket *src);
  */
 int av_packet_copy_props(AVPacket *dst, const AVPacket *src);
 
+/**
+ * Convert valid timing fields (timestamps / durations) in a packet from one
+ * timebase to another. Timestamps with unknown values (AV_NOPTS_VALUE) will be
+ * ignored.
+ *
+ * @param pkt packet on which the conversion will be performed
+ * @param tb_src source timebase, in which the timing fields in pkt are
+ *               expressed
+ * @param tb_dst destination timebase, to which the timing fields will be
+ *               converted
+ */
+void av_packet_rescale_ts(AVPacket *pkt, AVRational tb_src, AVRational tb_dst);
+
 /**
  * @}
  */

libavcodec/avpacket.c

@@ -24,6 +24,7 @@
 #include "libavutil/avassert.h"
 #include "libavutil/common.h"
 #include "libavutil/internal.h"
+#include "libavutil/mathematics.h"
 #include "libavutil/mem.h"
 #include "avcodec.h"
 #if FF_API_DESTRUCT_PACKET
@@ -380,3 +381,15 @@ void av_packet_move_ref(AVPacket *dst, AVPacket *src)
     *dst = *src;
     av_init_packet(src);
 }
+
+void av_packet_rescale_ts(AVPacket *pkt, AVRational src_tb, AVRational dst_tb)
+{
+    if (pkt->pts != AV_NOPTS_VALUE)
+        pkt->pts = av_rescale_q(pkt->pts, src_tb, dst_tb);
+    if (pkt->dts != AV_NOPTS_VALUE)
+        pkt->dts = av_rescale_q(pkt->dts, src_tb, dst_tb);
+    if (pkt->duration > 0)
+        pkt->duration = av_rescale_q(pkt->duration, src_tb, dst_tb);
+    if (pkt->convergence_duration > 0)
+        pkt->convergence_duration = av_rescale_q(pkt->convergence_duration, src_tb, dst_tb);
+}

libavcodec/version.h

@@ -29,7 +29,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVCODEC_VERSION_MAJOR 55
-#define LIBAVCODEC_VERSION_MINOR 54
+#define LIBAVCODEC_VERSION_MINOR 55
 #define LIBAVCODEC_VERSION_MICRO  0
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \