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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
#include "beep.h"
#include "rdp.h"
#include "settings.h"
#include <freerdp/freerdp.h>
#include <guacamole/audio.h>
#include <guacamole/client.h>
#include <winpr/wtypes.h>
#include <inttypes.h>
#include <stdlib.h>
#include <string.h>
* Fills the given buffer with signed 8-bit, single-channel PCM at the given
* sample rate which will produce a beep of the given frequency.
* @param buffer
* The buffer to fill with PCM data.
* @param frequency
* The frequency of the beep to generate, in hertz.
* @param rate
* The sample rate of the PCM to generate, in samples per second.
* @param buffer_size
* The number of bytes of PCM data to write to the given buffer.
static void guac_rdp_beep_fill_triangle_wave(unsigned char* buffer,
int frequency, int rate, int buffer_size) {
/* With the distance between each positive/negative peak and zero being the
* amplitude, and with the "bounce" between those peaks occurring once
* every two periods, the number of distinct states that the triangle wave
* function goes through is twice the peak-to-peak amplitude, or four times
* the overall amplitude */
const int wave_period = GUAC_RDP_BEEP_AMPLITUDE * 4;
/* With the number of distinct states being the wave_period defined above,
* the "bounce" point within that period is half the period */
const int wave_bounce_offset = wave_period / 2;
for (int position = 0; position < buffer_size; position++) {
/* Calculate relative position within the repeating portion of the wave
* (the portion with wave_period unique states) */
int wave_position = (position * frequency * wave_period / rate) % wave_period;
/* Calculate state of the triangle wave function at the calculated
* offset, knowing in advance the relative location that the function
* should "bounce" */
*(buffer++) = abs(wave_position - wave_bounce_offset) - GUAC_RDP_BEEP_AMPLITUDE;
* Writes PCM data to the given guac_audio_stream which produces a beep of the
* given frequency and duration. The provided guac_audio_stream may be
* configured for any sample rate but MUST be configured for single-channel,
* 8-bit PCM.
* @param audio
* The guac_audio_stream which should receive the PCM data.
* @param frequency
* The frequency of the beep, in hertz.
* @param duration
* The duration of the beep, in milliseconds.
static void guac_rdp_beep_write_pcm(guac_audio_stream* audio,
int frequency, int duration) {
int buffer_size = audio->rate * duration / 1000;
unsigned char* buffer = malloc(buffer_size);
/* Beep for given frequency/duration using a simple triangle wave */
guac_rdp_beep_fill_triangle_wave(buffer, frequency, audio->rate, buffer_size);
guac_audio_stream_write_pcm(audio, buffer, buffer_size);
BOOL guac_rdp_beep_play_sound(rdpContext* context,
const PLAY_SOUND_UPDATE* play_sound) {
guac_client* client = ((rdp_freerdp_context*) context)->client;
guac_rdp_client* rdp_client = (guac_rdp_client*) client->data;
guac_rdp_settings* settings = rdp_client->settings;
/* Ignore if audio is not enabled */
if (!settings->audio_enabled) {
guac_client_log(client, GUAC_LOG_DEBUG, "Ignoring request to beep "
"for %" PRIu32 " millseconds at %" PRIu32 " Hz as audio is "
"disabled.", play_sound->duration, play_sound->frequency);
return TRUE;
/* Allocate audio stream which sends audio in a format supported by the
* connected client(s) */
guac_audio_stream* beep = guac_audio_stream_alloc(client, NULL,
/* Stream availability is not guaranteed */
if (beep == NULL) {
guac_client_log(client, GUAC_LOG_DEBUG, "Ignoring request to beep "
"for %" PRIu32 " millseconds at %" PRIu32 " Hz as no audio "
"stream could be allocated.", play_sound->duration,
return TRUE;
/* Limit maximum duration of each beep */
int duration = play_sound->duration;
guac_rdp_beep_write_pcm(beep, play_sound->frequency, duration);
return TRUE;