jitter.c

一个开源SIP协议栈

   late_ratio_short = 0;
   late_ratio_long = 0;
   for (i=0;i<LATE_BINS;i++)
   {
      late_ratio_short += jitter->shortterm_margin[i];
      late_ratio_long += jitter->longterm_margin[i];
   }
   ontime_ratio_short = jitter->shortterm_margin[LATE_BINS];
   ontime_ratio_long = jitter->longterm_margin[LATE_BINS];
   early_ratio_short = early_ratio_long = 0;
   for (i=LATE_BINS+1;i<MAX_MARGIN;i++)
   {
      early_ratio_short += jitter->shortterm_margin[i];
      early_ratio_long += jitter->longterm_margin[i];
   }
   if (0&&jitter->pointer_timestamp%1000==0)
   {
      /*fprintf (stderr, "%f %f %f %f %f %f\n", early_ratio_short, early_ratio_long, ontime_ratio_short, ontime_ratio_long, late_ratio_short, late_ratio_long);*/
      /*fprintf (stderr, "%f %f\n", early_ratio_short + ontime_ratio_short + late_ratio_short, early_ratio_long + ontime_ratio_long + late_ratio_long);*/
   }
   
   /* Adjusting the buffering */
   
   if (late_ratio_short > .1 || late_ratio_long > .03)
   {
      /* If too many packets are arriving late */
      jitter->shortterm_margin[MAX_MARGIN-1] += jitter->shortterm_margin[MAX_MARGIN-2];
      jitter->longterm_margin[MAX_MARGIN-1] += jitter->longterm_margin[MAX_MARGIN-2];
      for (i=MAX_MARGIN-3;i>=0;i--)
      {
         jitter->shortterm_margin[i+1] = jitter->shortterm_margin[i];
         jitter->longterm_margin[i+1] = jitter->longterm_margin[i];         
      }
      jitter->shortterm_margin[0] = 0;
      jitter->longterm_margin[0] = 0;            
      jitter->pointer_timestamp -= jitter->tick_size;
      jitter->current_timestamp -= jitter->tick_size;
      /*fprintf (stderr, "i");*/
      /*fprintf (stderr, "interpolate (getting some slack)\n");*/
   } else if (late_ratio_short + ontime_ratio_short < .005 && late_ratio_long + ontime_ratio_long < .01 && early_ratio_short > .8)
   {
      /* Many frames arriving early */
      jitter->shortterm_margin[0] += jitter->shortterm_margin[1];
      jitter->longterm_margin[0] += jitter->longterm_margin[1];
      for (i=1;i<MAX_MARGIN-1;i++)
      {
         jitter->shortterm_margin[i] = jitter->shortterm_margin[i+1];
         jitter->longterm_margin[i] = jitter->longterm_margin[i+1];         
      }
      jitter->shortterm_margin[MAX_MARGIN-1] = 0;
      jitter->longterm_margin[MAX_MARGIN-1] = 0;      
      /*fprintf (stderr, "drop frame\n");*/
      /*fprintf (stderr, "d");*/
      jitter->pointer_timestamp += jitter->tick_size;
      jitter->current_timestamp += jitter->tick_size;
      /*fprintf (stderr, "dropping packet (getting more aggressive)\n");*/
   }
   
   /* Searching for the packet that fits best */
   
   /* Search the buffer for a packet with the right timestamp and spanning the whole current chunk */
   for (i=0;i<SPEEX_JITTER_MAX_BUFFER_SIZE;i++)
   {
      if (jitter->buf[i] && jitter->timestamp[i]==jitter->pointer_timestamp && GE32(jitter->timestamp[i]+jitter->span[i],jitter->pointer_timestamp+chunk_size))
         break;
   }
   
   /* If no match, try for an "older" packet that still spans (fully) the current chunk */
   if (i==SPEEX_JITTER_MAX_BUFFER_SIZE)
   {
      for (i=0;i<SPEEX_JITTER_MAX_BUFFER_SIZE;i++)
      {
         if (jitter->buf[i] && jitter->timestamp[i]<=jitter->pointer_timestamp && GE32(jitter->timestamp[i]+jitter->span[i],jitter->pointer_timestamp+chunk_size))
            break;
      }
   }
   
   /* If still no match, try for an "older" packet that spans part of the current chunk */
   if (i==SPEEX_JITTER_MAX_BUFFER_SIZE)
   {
      for (i=0;i<SPEEX_JITTER_MAX_BUFFER_SIZE;i++)
      {
         if (jitter->buf[i] && jitter->timestamp[i]<=jitter->pointer_timestamp && GT32(jitter->timestamp[i]+jitter->span[i],jitter->pointer_timestamp))
            break;
      }
   }
   
   /* If still no match, try for earliest packet possible */
   if (i==SPEEX_JITTER_MAX_BUFFER_SIZE)
   {
      int found = 0;
      spx_uint32_t best_time=0;
      int best_span=0;
      int besti=0;
      for (i=0;i<SPEEX_JITTER_MAX_BUFFER_SIZE;i++)
      {
         /* check if packet starts within current chunk */
         if (jitter->buf[i] && LT32(jitter->timestamp[i],jitter->pointer_timestamp+chunk_size) && GE32(jitter->timestamp[i],jitter->pointer_timestamp))
         {
            if (!found || LT32(jitter->timestamp[i],best_time) || (jitter->timestamp[i]==best_time && GT32(jitter->span[i],best_span)))
            {
               best_time = jitter->timestamp[i];
               best_span = jitter->span[i];
               besti = i;
               found = 1;
            }
         }
      }
      if (found)
      {
         i=besti;
         incomplete = 1;
         /*fprintf (stderr, "incomplete: %d %d %d %d\n", jitter->timestamp[i], jitter->pointer_timestamp, chunk_size, jitter->span[i]);*/
      }
   }

   /* If we find something */
   if (i!=SPEEX_JITTER_MAX_BUFFER_SIZE)
   {
      /* We (obviously) haven't lost this packet */
      jitter->lost_count = 0;
      jitter->loss_rate = .999*jitter->loss_rate;
      /* Check for potential overflow */
      packet->len = jitter->len[i];
      /* Copy packet */
      for (j=0;j<packet->len;j++)
         packet->data[j] = jitter->buf[i][j];
      /* Remove packet */
      speex_free(jitter->buf[i]);
      jitter->buf[i] = NULL;
      /* Set timestamp and span (if requested) */
      if (start_offset)
         *start_offset = jitter->timestamp[i]-jitter->pointer_timestamp;
      packet->timestamp = jitter->timestamp[i];
      packet->span = jitter->span[i];
      /* Point at the end of the current packet */
      jitter->pointer_timestamp = jitter->timestamp[i]+jitter->span[i];
      if (incomplete)
         return JITTER_BUFFER_INCOMPLETE;
      else
         return JITTER_BUFFER_OK;
   }
   
   
   /* If we haven't found anything worth returning */
   /*fprintf (stderr, "not found\n");*/
   jitter->lost_count++;
   /*fprintf (stderr, "m");*/
   /*fprintf (stderr, "lost_count = %d\n", jitter->lost_count);*/
   jitter->loss_rate = .999*jitter->loss_rate + .001;
   if (start_offset)
      *start_offset = 0;
   packet->timestamp = jitter->pointer_timestamp;
   packet->span = jitter->tick_size;
   jitter->pointer_timestamp += chunk_size;
   packet->len = 0;
   return JITTER_BUFFER_MISSING;

}

/** Get pointer timestamp of jitter buffer */
int jitter_buffer_get_pointer_timestamp(JitterBuffer *jitter)
{
   return jitter->pointer_timestamp;
}

void jitter_buffer_tick(JitterBuffer *jitter)
{
   jitter->current_timestamp += jitter->tick_size;
}





void speex_jitter_init(SpeexJitter *jitter, void *decoder, int sampling_rate)
{
   jitter->dec = decoder;
   speex_decoder_ctl(decoder, SPEEX_GET_FRAME_SIZE, &jitter->frame_size);

   jitter->packets = jitter_buffer_init(jitter->frame_size);

   speex_bits_init(&jitter->current_packet);
   jitter->valid_bits = 0;

}

void speex_jitter_destroy(SpeexJitter *jitter)
{
   jitter_buffer_destroy(jitter->packets);
   speex_bits_destroy(&jitter->current_packet);
}

void speex_jitter_put(SpeexJitter *jitter, char *packet, int len, int timestamp)
{
   JitterBufferPacket p;
   p.data = packet;
   p.len = len;
   p.timestamp = timestamp;
   p.span = jitter->frame_size;
   jitter_buffer_put(jitter->packets, &p);
}

void speex_jitter_get(SpeexJitter *jitter, short *out, int *current_timestamp)
{
   int i;
   int ret;
   char data[2048];
   JitterBufferPacket packet;
   packet.data = data;
   
   if (jitter->valid_bits)
   {
      /* Try decoding last received packet */
      ret = speex_decode_int(jitter->dec, &jitter->current_packet, out);
      if (ret == 0)
      {
         jitter_buffer_tick(jitter->packets);
         return;
      } else {
         jitter->valid_bits = 0;
      }
   }

   ret = jitter_buffer_get(jitter->packets, &packet, NULL);
   
   if (ret != JITTER_BUFFER_OK)
   {
      /* No packet found */

      /*fprintf (stderr, "lost/late frame\n");*/
      /*Packet is late or lost*/
      speex_decode_int(jitter->dec, NULL, out);
   } else {
      speex_bits_read_from(&jitter->current_packet, packet.data, packet.len);
      /* Decode packet */
      ret = speex_decode_int(jitter->dec, &jitter->current_packet, out);
      if (ret == 0)
      {
         jitter->valid_bits = 1;
      } else {
         /* Error while decoding */
         for (i=0;i<jitter->frame_size;i++)
            out[i]=0;
      }
   }
   jitter_buffer_tick(jitter->packets);
}

int speex_jitter_get_pointer_timestamp(SpeexJitter *jitter)
{
   return jitter_buffer_get_pointer_timestamp(jitter->packets);
}