.VAR audio_out_dc_remove_op_mono.param[$cbops.dc_remove.STRUC_SIZE] =
               0,                         // Input index
               0;                         // Output index
   .ENDBLOCK;

   .BLOCK $audio_out_warp_and_shift_op_mono;
      .VAR audio_out_warp_and_shift_op_mono.next = $cbops.NO_MORE_OPERATORS;
      .VAR audio_out_warp_and_shift_op_mono.func = &$cbops.warp_and_shift;
      .VAR audio_out_warp_and_shift_op_mono.param[$cbops.warp_and_shift.STRUC_SIZE] =
               0,                         // Input index
               1,                         // Output index
               -8,                        // Shift amount
               &$WARP_FILTER_COEFS,                                                    // warp filter coefs
               &audio_out_warp_and_shift_op.left_buf,                                  // warp filter buffer
               &$decoder_codec_stream_struc + $codec.stream_decode.WARP_TARGET_FIELD,  // warp target address
               (WARP_RATE_MAX_RAMP / 1000000 * TMR_PERIOD_AUDIO_COPY);                 // warp rate max ramp
   .ENDBLOCK;

   .VAR/DM1CIRC audio_out_warp_and_shift_op.left_buf[$WARP_FILTER_LENGTH];
   .VAR/DM1CIRC audio_out_warp_and_shift_op.right_buf[$WARP_FILTER_LENGTH];


   // ** allocate memory for codec stream structure **
   .VAR/DM1 $decoder_codec_stream_struc[$codec.stream_decode.STRUC_SIZE] =
            SELECTED_CODEC_FRAME_DECODE_FUNCTION,    // frame_decode function
            SELECTED_CODEC_RESET_DECODER_FUNCTION,   // reset_decoder function
            SELECTED_CODEC_SILENCE_DECODER_FUNCTION, // silence_decoder function
            &$codec_in_cbuffer_struc,                // in cbuffer
            &$audio_out_left_cbuffer_struc,          // out left cbuffer
            &$audio_out_right_cbuffer_struc,         // out right cbuffer
            0,                                       // internal mode data
            0,                                       // internal state data
            COMFORT_NOISE_GAIN,                      // comfort noise gain
            GOOD_WORKING_BUFFER_LEVEL,               // good working buffer level %
            POORLINK_DETECT_LEVEL,                   // poorlink detect buffer level %
            POORLINK_PERIOD,                         // poorlink period (us)
            ZERO_DATA_RATE_STOPPING,                 // playing -> stopping
                                                     // zero datarate period (us)
            ZERO_DATA_RATE_BUFFERING,                // buffering -> play out buffer
                                                     // zero datarate period (us)
            &poorlink_detect_table,                  // poorlink detect table address
            LENGTH(poorlink_detect_table),           // poorlink detect table size
            (WARP_RATE_HIGH_COEFFICIENT / 500),      // warp rate high coefficient
            (WARP_RATE_LOW_COEFFICIENT / 500),       // warp rate low coefficient
            WARP_RATE_TRANSITION_LEVEL_WORDS;        // warp transition level in words
   .VAR poorlink_detect_table[300];


   // initialise the stack library
   call $stack.initialise;
   // initialise the interrupt library
   call $interrupt.initialise;
   // initialise the message library
   call $message.initialise;
   // initialise the cbuffer library
   call $cbuffer.initialise;
   .ifdef DEBUG_ON
      // initialise the profiler library
      call $profiler.initialise;
   .endif

   // initialise the codec decoder library
   call SELECTED_CODEC_INITIALISE_DECODER_FUNCTION;

   // tell vm we're ready and wait for the go message
   call $message.send_ready_wait_for_go;


   // see if left output port is connected
   r0 = $AUDIO_LEFT_OUT_PORT;
   call $cbuffer.is_it_enabled;
   if NZ jump left_port_connected;
      // tell codec library that no left buffer
      M[$decoder_codec_stream_struc + $codec.stream_decode.OUT_LEFT_BUFFER_FIELD] = 0;
   left_port_connected:


   // see if right output port is connected
   r0 = $AUDIO_RIGHT_OUT_PORT;
   call $cbuffer.is_it_enabled;
   if NZ jump right_port_connected;
      // tell codec library that no right buffer
      M[$decoder_codec_stream_struc + $codec.stream_decode.OUT_RIGHT_BUFFER_FIELD] = 0;
   right_port_connected:


   // wait for DAC buffers to have just wrapped around
   wait_for_dac_buffer_wraparound:
      r0 = $AUDIO_LEFT_OUT_PORT;
      call $cbuffer.calc_amount_space;
      // if the amount of space in the buffer is less than 16 bytes then a
      // buffer wrap around must have just ocurred.
      Null = r0 - 16;
   if POS jump wait_for_dac_buffer_wraparound;


   // start timer that copies output samples
   r1 = &$audio_out_timer_struc;
   r2 = TMR_PERIOD_AUDIO_COPY;
   r3 = &$audio_out_copy_handler;
   call $timer.schedule_event_in;

   // start timer that copies codec input data
   r1 = &$codec_in_timer_struc;
   r2 = TMR_PERIOD_CODEC_COPY;
   r3 = &$codec_in_copy_handler;
   call $timer.schedule_event_in;

   // continually decode codec frames
   frame_loop:

      // decode a frame
      r5 = &$decoder_codec_stream_struc;
      call $codec.stream_decode;
      // idle as much as we can
      Null = r0 - $codec.STREAM_CAN_IDLE;
      if Z call $timer.1ms_delay;

   jump frame_loop;

.ENDMODULE;





// *****************************************************************************
// MODULE:
//    $audio_out_copy_handler
//
// DESCRIPTION:
//    Function called on a timer interrupt to perform the mono or stereo copying
//    of decoded samples to the output.
//
// *****************************************************************************
.MODULE $M.audio_out_copy_handler;
   .CODESEGMENT PM;
   .DATASEGMENT DM;

   $audio_out_copy_handler:

   // push rLink onto stack
   $push_rLink_macro;

   r8 = &$stereo_out_copy_struc;
   r7 = &$mono_out_copy_struc;
   // see if mono or stereo connection, based on whether the right output port
   // is enabled
   r0 = $AUDIO_RIGHT_OUT_PORT;
   call $cbuffer.is_it_enabled;
   if Z r8 = r7;

   // Call the copy routine
   call $cbops.copy;

   // post another timer event
   r1 = &$audio_out_timer_struc;
   r2 = TMR_PERIOD_AUDIO_COPY;
   r3 = &$audio_out_copy_handler;
   call $timer.schedule_event_in_period;

   // pop rLink from stack
   jump $pop_rLink_and_rts;

.ENDMODULE;





// *****************************************************************************
// MODULE:
//    $codec_in_copy_handler
//
// DESCRIPTION:
//    Function called on a timer interrupt to perform the copying of encoded
//    samples from the input.
//
// *****************************************************************************
.MODULE $M.codec_in_copy_handler;
   .CODESEGMENT PM;
   .DATASEGMENT DM;

   $codec_in_copy_handler:

   // push rLink onto stack
   $push_rLink_macro;

   // copy data from the port to the cbuffer
   r8 = &$codec_in_copy_struc;
   call $cbops.copy;

   // post another timer event
   r1 = &$codec_in_timer_struc;
   r2 = TMR_PERIOD_CODEC_COPY;
   r3 = &$codec_in_copy_handler;
   call $timer.schedule_event_in_period;

   // pop rLink from stack
   jump $pop_rLink_and_rts;

.ENDMODULE;