Differences

This shows you the differences between two versions of the page.

--- resources:tools-software:sharc-audio-module:baremetal:chaining-audio-elements [13 Dec 2018 17:28] – Dan Ledger
+++ resources:tools-software:sharc-audio-module:baremetal:chaining-audio-elements [06 Feb 2019 17:53] (current) – Chad Wentworth
@@ Line 3: / Line 3: @@
 The power of the audio elements is how they can be combined in novel ways to create audio effects.  In this tutorial, we'll implement a bank of band-pass filters that feed into a set of different delay lines set to different delay lengths.
-To do this, we'll first need to declare instances of the biquad and integer_delay_lpf audio elements.
+To do this, we'll first need to declare instances of the biquad and integer_delay_lpf audio elements at the top of ''src/callback_audio_processing.cpp'' on the first SHARC core.
 <code c>
-// Declarations for struct/instances for filters and delay lines
+// Declarations for struct/instances for filters
-BIQUAD_FILTER filt_300Hz, filt_450Hz, filt_600_Hz, filt_800Hz, filt_1000Hz;
+BIQUAD_FILTER filt_300Hz, filt_900Hz;
-float pm filt_300Hz_coeffs[4];
 float pm filt_300Hz_coeffs[4];
+float pm filt_900Hz_coeffs[4];
-DELAY_LPF     delay_1, delay_2, delay_3;
+// Declaration of delay element structs and buffers for delay lines
+DELAY_LPF     delay_1, delay_2;
-// Declaration of memory buffers in SDRAM used for the delay lines that will be 2 seconds long (max)
 float    section("seg_sdram") delay_buffer_1[AUDIO_SAMPLE_RATE*2];
 float    section("seg_sdram") delay_buffer_2[AUDIO_SAMPLE_RATE*2];
-float    section("seg_sdram") delay_buffer_3[AUDIO_SAMPLE_RATE*2];
 </code>
@@ Line 29: / Line 27: @@
     // *******************************************************************************
+    // Set up filters
+    filter_setup(&filt_300Hz,
+                 BIQUAD_TYPE_BPF,
+                 BIQUAD_TRANS_MED,
+                 filt_300Hz_coeffs,
+.0,  // Center frequency
+.0,    // Q
+.0,    // Gain (db)
+                 AUDIO_SAMPLE_RATE);
+    filter_setup(&filt_900Hz,
+                 BIQUAD_TYPE_BPF,
+                 BIQUAD_TRANS_MED,
+                 filt_900Hz_coeffs,
+.0,  // Center frequency
+.0,    // Q
+.0,    // Gain (db)
+                 AUDIO_SAMPLE_RATE);
+    // Set up delay lines
+    delay_setup(&delay_1,
+                delay_buffer_1,
+                AUDIO_SAMPLE_RATE*2,
+                AUDIO_SAMPLE_RATE*0.25, // set delay line initially to 0.25 seconds
+.8,  // Feedthrough
+.6,  // Feedback
+.0); // Dampening coefficient (0=no dampening)
+    delay_setup(&delay_2,
+                delay_buffer_2,
+                AUDIO_SAMPLE_RATE*2,
+                AUDIO_SAMPLE_RATE*0.5, // set delay line initially to 0.5 seconds
+.8,  // Feedthrough
+.6,  // Feedback
+.0); // Dampening coefficient (0=no dampening)
+}
+</code>
+Finally, we'll process audio in ''void processaudio_callback(void)''.  First, we will run the biquads on the incoming left and right audio channels and save the outputs to a pair of buffers called 'audio_temp_1' and 'audio_temp_2'.  We'll then use these buffers as the inputs to our delay functions.  Finally, we'll send the outputs of the delay function to the left channel and right channel outputs.
+<code c>
+void processaudio_callback(void) {
+    float audio_temp_1[AUDIO_BLOCK_SIZE];
+    float audio_temp_2[AUDIO_BLOCK_SIZE];
+    // Run filters on incoming L/R input audio
+    filter_read(&filt_300Hz, audiochannel_0_left_in, audio_temp_1, AUDIO_BLOCK_SIZE);
+    filter_read(&filt_900Hz, audiochannel_0_right_in, audio_temp_2, AUDIO_BLOCK_SIZE);
+    // Run filtered audio through delay lines and send to L/R/ output audio
+    delay_read(&delay_1, audio_temp_1, audiochannel_0_left_out, AUDIO_BLOCK_SIZE);
+    delay_read(&delay_2, audio_temp_2, audiochannel_0_right_out, AUDIO_BLOCK_SIZE);
 }
 </code>
+----
+{{navigation SHARC Audio Module#volume-control-tutorial|Programming a Volume Control#.|Bare Metal Framework#class-d-2-1-amp|Building a 2.1 Amplifier}}

Wiki

Analog Devices Wiki

Differences

Analog Devices Wiki

Differences

Page Tools