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Calculate timestamps from packet durations.

Previously, everything was hard-coded to 20 ms. Now we increment
rtp timestamps and ogg granulepos based on the packet duration
as described by the ToC header.

This adds a dependency on libopus, but the opus_packet() calls
as small and can stand alone, so they could be extracted and
supplied separately if necessary.

Granulepos values are still ignored when reading from a .opus
file. It would probably be better to either warn, or use those
as much as possible to set the rtp timestamps to better represent
the recorded data.

--- a/Makefile.am

+++ b/Makefile.am

@@ -56,6 +56,6 @@

 opusinfo_MANS = man/opusinfo.1

 opusrtp_SOURCES = src/opusrtp.c

-opusrtp_LDADD = @LIBPCAP@ $(OGG_LIBS)

+opusrtp_LDADD = @LIBPCAP@ $(OGG_LIBS) $(Opus_LIBS)

 #TESTS = FIXME

--- a/Makefile.unix

+++ b/Makefile.unix

@@ -21,7 +21,7 @@

 	$(CC) $(LDFLAGS) src/opus_header.o src/opusinfo.o src/info_opus.o -o opusinfo -logg

 opusrtp: src/opusrtp.o

-	$(CC) $(LDFLAGS) src/opusrtp.o -o opusrtp -logg

+	$(CC) $(LDFLAGS) src/opusrtp.o -o opusrtp ../opus/.libs/libopus.a -logg

 clean:

 	rm -f src/*.o $(PROGS) opusrtp

--- a/src/opusrtp.c

+++ b/src/opusrtp.c

@@ -58,6 +58,7 @@

 #ifdef HAVE_PCAP

 #include <pcap.h>

 #endif

+#include <opus.h>

 #include <ogg/ogg.h>

 #define OPUS_PAYLOAD_TYPE 113

@@ -67,6 +68,7 @@

   ogg_stream_state *stream;

   FILE *out;

   int seq;

+  ogg_int64_t granulepos;

   int linktype;

 } state;

@@ -215,7 +217,17 @@

   return 0;

 }

+/* calculate the number of samples in an opus packet */

+int opus_samples(const unsigned char *packet, int size)

+{

+  /* number of samples per frame at 48 kHz */

+  int samples = opus_packet_get_samples_per_frame(packet, 48000);

+  /* number "frames" in this packet */

+  int frames = opus_packet_get_nb_frames(packet, size);

+  return samples*frames;

+}

+

 /* helper, write out available ogg pages */

 int ogg_write(state *params)

 {

@@ -588,6 +600,7 @@

     }

     /* read and process available packets */

     while (ogg_stream_packetout(&os,&op) == 1) {

+      int samples;

       /* skip header packets */

       if (state == 1 && op.bytes >= 19 && !memcmp(op.packet, "OpusHead", 8)) {

         state++;

@@ -597,13 +610,14 @@

         state++;

         continue;

       }

+      /* get packet duration */

+      samples = opus_samples(op.packet, op.bytes);

       /* update the rtp header and send */

-      rtp.time += 960;

-      // TODO: rtp.time += count_samples(op.packet, op.bytes);

       rtp.seq++;

+      rtp.time += samples;

       rtp.payload_size = op.bytes;

       send_rtp_packet(fd, (struct sockaddr *)&sin, &rtp, op.packet);

-      usleep(20000);

+      usleep(samples*1000/48);

     }

   }

   }

@@ -733,7 +747,9 @@

   /* write the payload to our opus file */

   ogg_packet *op = op_from_pkt(packet, size);

-  op->granulepos = 960*rtp.seq; // FIXME: get this from the toc byte

+  op->packetno = rtp.seq;

+  params->granulepos += opus_samples(packet, size);

+  op->granulepos = params->granulepos;

   ogg_stream_packetin(params->stream, op);

   free(op);

   ogg_write(params);

@@ -783,6 +799,7 @@

     return -2;

   }

   params->seq = 0;

+  params->granulepos = 0;

   /* write stream headers */

   op = op_opushead();