jitter.c

mediastreamer2是开源的网络传输媒体流的库

         int earliest=jitter->packets[0].timestamp;
         i=0;
         for (j=1;j<SPEEX_JITTER_MAX_BUFFER_SIZE;j++)
         {
            if (!jitter->packets[i].data || LT32(jitter->packets[j].timestamp,earliest))
            {
               earliest = jitter->packets[j].timestamp;
               i=j;
            }
         }
         if (jitter->destroy)
            jitter->destroy(jitter->packets[i].data);
         else
            speex_free(jitter->packets[i].data);
         jitter->packets[i].data=NULL;
         /*fprintf (stderr, "Buffer is full, discarding earliest frame %d (currently at %d)\n", timestamp, jitter->pointer_timestamp);*/      
      }
   
      /* Copy packet in buffer */
      if (jitter->destroy)
      {
         jitter->packets[i].data = packet->data;
      } else {
         jitter->packets[i].data=(char*)speex_alloc(packet->len);
         for (j=0;j<packet->len;j++)
            jitter->packets[i].data[j]=packet->data[j];
      }
      jitter->packets[i].timestamp=packet->timestamp;
      jitter->packets[i].span=packet->span;
      jitter->packets[i].len=packet->len;
      jitter->packets[i].sequence=packet->sequence;
      jitter->packets[i].user_data=packet->user_data;
      if (jitter->reset_state || late)
         jitter->arrival[i] = 0;
      else
         jitter->arrival[i] = jitter->next_stop;
   }
   
   
}

/** Get one packet from the jitter buffer */
EXPORT int jitter_buffer_get(JitterBuffer *jitter, JitterBufferPacket *packet, spx_int32_t desired_span, spx_int32_t *start_offset)
{
   int i;
   unsigned int j;
   int incomplete = 0;
   spx_int16_t opt;
   
   if (start_offset != NULL)
      *start_offset = 0;

   /* Syncing on the first call */
   if (jitter->reset_state)
   {
      int found = 0;
      /* Find the oldest packet */
      spx_uint32_t oldest=0;
      for (i=0;i<SPEEX_JITTER_MAX_BUFFER_SIZE;i++)
      {
         if (jitter->packets[i].data && (!found || LT32(jitter->packets[i].timestamp,oldest)))
         {
            oldest = jitter->packets[i].timestamp;
            found = 1;
         }
      }
      if (found)
      {
         jitter->reset_state=0;         
         jitter->pointer_timestamp = oldest;
         jitter->next_stop = oldest;
      } else {
         packet->timestamp = 0;
         packet->span = jitter->interp_requested;
         return JITTER_BUFFER_MISSING;
      }
   }
   

   jitter->last_returned_timestamp = jitter->pointer_timestamp;
         
   if (jitter->interp_requested != 0)
   {
      packet->timestamp = jitter->pointer_timestamp;
      packet->span = jitter->interp_requested;
      
      /* Increment the pointer because it got decremented in the delay update */
      jitter->pointer_timestamp += jitter->interp_requested;
      packet->len = 0;
      /*fprintf (stderr, "Deferred interpolate\n");*/
      
      jitter->interp_requested = 0;
      
      jitter->buffered = packet->span - desired_span;

      return JITTER_BUFFER_INSERTION;
   }
   
   /* 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->packets[i].data && jitter->packets[i].timestamp==jitter->pointer_timestamp && GE32(jitter->packets[i].timestamp+jitter->packets[i].span,jitter->pointer_timestamp+desired_span))
         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->packets[i].data && LE32(jitter->packets[i].timestamp, jitter->pointer_timestamp) && GE32(jitter->packets[i].timestamp+jitter->packets[i].span,jitter->pointer_timestamp+desired_span))
            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->packets[i].data && LE32(jitter->packets[i].timestamp, jitter->pointer_timestamp) && GT32(jitter->packets[i].timestamp+jitter->packets[i].span,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->packets[i].data && LT32(jitter->packets[i].timestamp,jitter->pointer_timestamp+desired_span) && GE32(jitter->packets[i].timestamp,jitter->pointer_timestamp))
         {
            if (!found || LT32(jitter->packets[i].timestamp,best_time) || (jitter->packets[i].timestamp==best_time && GT32(jitter->packets[i].span,best_span)))
            {
               best_time = jitter->packets[i].timestamp;
               best_span = jitter->packets[i].span;
               besti = i;
               found = 1;
            }
         }
      }
      if (found)
      {
         i=besti;
         incomplete = 1;
         /*fprintf (stderr, "incomplete: %d %d %d %d\n", jitter->packets[i].timestamp, jitter->pointer_timestamp, chunk_size, jitter->packets[i].span);*/
      }
   }

   /* If we find something */
   if (i!=SPEEX_JITTER_MAX_BUFFER_SIZE)
   {
      spx_int32_t offset;
      
      /* We (obviously) haven't lost this packet */
      jitter->lost_count = 0;
      
      /* In this case, 0 isn't as a valid timestamp */
      if (jitter->arrival[i] != 0)
      {
         update_timings(jitter, ((spx_int32_t)jitter->packets[i].timestamp) - ((spx_int32_t)jitter->arrival[i]) - jitter->buffer_margin);
      }
      
      
      /* Copy packet */
      if (jitter->destroy)
      {
         packet->data = jitter->packets[i].data;
         packet->len = jitter->packets[i].len;
      } else {
         if (jitter->packets[i].len > packet->len)
         {
            speex_warning_int("jitter_buffer_get(): packet too large to fit. Size is", jitter->packets[i].len);
         } else {
            packet->len = jitter->packets[i].len;
         }
         for (j=0;j<packet->len;j++)
            packet->data[j] = jitter->packets[i].data[j];
         /* Remove packet */
         speex_free(jitter->packets[i].data);
      }
      jitter->packets[i].data = NULL;
      /* Set timestamp and span (if requested) */
      offset = (spx_int32_t)jitter->packets[i].timestamp-(spx_int32_t)jitter->pointer_timestamp;
      if (start_offset != NULL)
         *start_offset = offset;
      else if (offset != 0)
         speex_warning_int("jitter_buffer_get() discarding non-zero start_offset", offset);
      
      packet->timestamp = jitter->packets[i].timestamp;
      jitter->last_returned_timestamp = packet->timestamp;
      
      packet->span = jitter->packets[i].span;
      packet->sequence = jitter->packets[i].sequence;
      packet->user_data = jitter->packets[i].user_data;
      /* Point to the end of the current packet */
      jitter->pointer_timestamp = jitter->packets[i].timestamp+jitter->packets[i].span;

      jitter->buffered = packet->span - desired_span;
      
      if (start_offset != NULL)
         jitter->buffered += *start_offset;
      
      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);*/
   
   opt = compute_opt_delay(jitter);
   
   /* Should we force an increase in the buffer or just do normal interpolation? */   
   if (opt < 0)
   {
      /* Need to increase buffering */
      
      /* Shift histogram to compensate */
      shift_timings(jitter, -opt);
      
      packet->timestamp = jitter->pointer_timestamp;
      packet->span = -opt;
      /* Don't move the pointer_timestamp forward */
      packet->len = 0;
      
      jitter->buffered = packet->span - desired_span;
      return JITTER_BUFFER_INSERTION;
      /*jitter->pointer_timestamp -= jitter->delay_step;*/
      /*fprintf (stderr, "Forced to interpolate\n");*/
   } else {
      /* Normal packet loss */
      packet->timestamp = jitter->pointer_timestamp;
      
      desired_span = ROUND_DOWN(desired_span, jitter->concealment_size);
      packet->span = desired_span;
      jitter->pointer_timestamp += desired_span;
      packet->len = 0;
      
      jitter->buffered = packet->span - desired_span;
      return JITTER_BUFFER_MISSING;
      /*fprintf (stderr, "Normal loss\n");*/
   }


}

EXPORT int jitter_buffer_get_another(JitterBuffer *jitter, JitterBufferPacket *packet)
{
   int i, j;
   for (i=0;i<SPEEX_JITTER_MAX_BUFFER_SIZE;i++)
   {
      if (jitter->packets[i].data && jitter->packets[i].timestamp==jitter->last_returned_timestamp)
         break;
   }
   if (i!=SPEEX_JITTER_MAX_BUFFER_SIZE)
   {
      /* Copy packet */
      packet->len = jitter->packets[i].len;
      if (jitter->destroy)
      {
         packet->data = jitter->packets[i].data;
      } else {
         for (j=0;j<packet->len;j++)
            packet->data[j] = jitter->packets[i].data[j];
         /* Remove packet */
         speex_free(jitter->packets[i].data);
      }
      jitter->packets[i].data = NULL;
      packet->timestamp = jitter->packets[i].timestamp;
      packet->span = jitter->packets[i].span;
      packet->sequence = jitter->packets[i].sequence;
      packet->user_data = jitter->packets[i].user_data;
      return JITTER_BUFFER_OK;
   } else {
      packet->data = NULL;
      packet->len = 0;
      packet->span = 0;
      return JITTER_BUFFER_MISSING;
   }
}

/* Let the jitter buffer know it's the right time to adjust the buffering delay to the network conditions */
static int _jitter_buffer_update_delay(JitterBuffer *jitter, JitterBufferPacket *packet, spx_int32_t *start_offset)
{
   spx_int16_t opt = compute_opt_delay(jitter);
   /*fprintf(stderr, "opt adjustment is %d ", opt);*/
   
   if (opt < 0)
   {
      shift_timings(jitter, -opt);
      
      jitter->pointer_timestamp += opt;
      jitter->interp_requested = -opt;
      /*fprintf (stderr, "Decision to interpolate %d samples\n", -opt);*/
   } else if (opt > 0)
   {
      shift_timings(jitter, -opt);
      jitter->pointer_timestamp += opt;
      /*fprintf (stderr, "Decision to drop %d samples\n", opt);*/
   }
   
   return opt;
}

/* Let the jitter buffer know it's the right time to adjust the buffering delay to the network conditions */
EXPORT int jitter_buffer_update_delay(JitterBuffer *jitter, JitterBufferPacket *packet, spx_int32_t *start_offset)
{
   /* If the programmer calls jitter_buffer_update_delay() directly, 
      automatically disable auto-adjustment */
   jitter->auto_adjust = 0;

   return _jitter_buffer_update_delay(jitter, packet, start_offset);
}

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

EXPORT void jitter_buffer_tick(JitterBuffer *jitter)
{
   /* Automatically-adjust the buffering delay if requested */
   if (jitter->auto_adjust)
      _jitter_buffer_update_delay(jitter, NULL, NULL);
   
   if (jitter->buffered >= 0)
   {
      jitter->next_stop = jitter->pointer_timestamp - jitter->buffered;
   } else {
      jitter->next_stop = jitter->pointer_timestamp;
      speex_warning_int("jitter buffer sees negative buffering, your code might be broken. Value is ", jitter->buffered);
   }
   jitter->buffered = 0;
}

EXPORT void jitter_buffer_remaining_span(JitterBuffer *jitter, spx_uint32_t rem)
{
   /* Automatically-adjust the buffering delay if requested */
   if (jitter->auto_adjust)
      _jitter_buffer_update_delay(jitter, NULL, NULL);
   
   if (jitter->buffered < 0)
      speex_warning_int("jitter buffer sees negative buffering, your code might be broken. Value is ", jitter->buffered);
   jitter->next_stop = jitter->pointer_timestamp - rem;
}


/* Used like the ioctl function to control the jitter buffer parameters */
EXPORT int jitter_buffer_ctl(JitterBuffer *jitter, int request, void *ptr)
{
   int count, i;
   switch(request)
   {
      case JITTER_BUFFER_SET_MARGIN:
         jitter->buffer_margin = *(spx_int32_t*)ptr;
         break;
      case JITTER_BUFFER_GET_MARGIN:
         *(spx_int32_t*)ptr = jitter->buffer_margin;
         break;
      case JITTER_BUFFER_GET_AVALIABLE_COUNT:
         count = 0;
         for (i=0;i<SPEEX_JITTER_MAX_BUFFER_SIZE;i++)
         {
            if (jitter->packets[i].data && LE32(jitter->pointer_timestamp, jitter->packets[i].timestamp))
            {
               count++;
            }
         }
         *(spx_int32_t*)ptr = count;
         break;
      case JITTER_BUFFER_SET_DESTROY_CALLBACK:
         jitter->destroy = (void (*) (void *))ptr;
         break;
      case JITTER_BUFFER_GET_DESTROY_CALLBACK:
         *(void (**) (void *))ptr = jitter->destroy;
         break;
      case JITTER_BUFFER_SET_DELAY_STEP:
         jitter->delay_step = *(spx_int32_t*)ptr;
         break;
      case JITTER_BUFFER_GET_DELAY_STEP:
         *(spx_int32_t*)ptr = jitter->delay_step;
         break;
      case JITTER_BUFFER_SET_CONCEALMENT_SIZE:
         jitter->concealment_size = *(spx_int32_t*)ptr;
         break;
      case JITTER_BUFFER_GET_CONCEALMENT_SIZE:
         *(spx_int32_t*)ptr = jitter->concealment_size;
         break;
      case JITTER_BUFFER_SET_MAX_LATE_RATE:
         jitter->max_late_rate = *(spx_int32_t*)ptr;
         jitter->window_size = 100*TOP_DELAY/jitter->max_late_rate;
         jitter->subwindow_size = jitter->window_size/MAX_BUFFERS;
         break;
      case JITTER_BUFFER_GET_MAX_LATE_RATE:
         *(spx_int32_t*)ptr = jitter->max_late_rate;
         break;
      case JITTER_BUFFER_SET_LATE_COST:
         jitter->latency_tradeoff = *(spx_int32_t*)ptr;
         break;
      case JITTER_BUFFER_GET_LATE_COST:
         *(spx_int32_t*)ptr = jitter->latency_tradeoff;
         break;
      default:
         speex_warning_int("Unknown jitter_buffer_ctl request: ", request);
         return -1;
   }
   return 0;
}