Increasing the volume of recording in Real Time of after saving it? - objective-c

Question

I used python to make a prototype, to increase the volume of audio signal in real time. It worked by using new_data = audioop.mul(data, 4, 4) where 'data' is chunks from Pyaudio in streaming.
Now, I have to apply similar in ObjectiveC, and even after searching I am unable to find it. How can it be done in Objective C? Do we have such control over data flow in Objective C and If we can't, Is there anyway that a recorded sample's volume can be increased?
import pyaudio
import wave
import audioop
import sys
FORMAT = pyaudio.paInt16
CHANNELS = 1
RATE = 44100
CHUNK = 1024
RECORD_SECONDS = 7
WAVE_OUTPUT_FILENAME1 = sys.argv[1]
WAVE_OUTPUT_FILENAME2 = sys.argv[2]
device_index = 2
print("----------------------record device list---------------------")
audio = pyaudio.PyAudio()
print(audio)
info = audio.get_host_api_info_by_index(0)
numdevices = info.get('deviceCount')
for i in range(0, numdevices):
if (audio.get_device_info_by_host_api_device_index(0, i).get('maxInputChannels')) > 0:
print ("Input Device id ", i, " - ", audio.get_device_info_by_host_api_device_index(0, i).get('name'))
print("-------------------------------------------------------------")
index = int((input()))
print(type(index))
print("recording via index "+str(index))
stream = audio.open(format=FORMAT, channels=CHANNELS,
rate=RATE, input=True,input_device_index = index,
frames_per_buffer=CHUNK)
print ("recording started")
Recordframes = []
Recordframes2= []
print(int(RATE / CHUNK * RECORD_SECONDS))
for i in range(0, int(RATE / CHUNK * RECORD_SECONDS)):
data = stream.read(CHUNK)
new_data = audioop.mul(data, 4, 4)
print("hshsh")
Recordframes.append(data)
Recordframes2.append(new_data)
# data = stream.read(CHUNK)
# print("hshsh")
# Recordframes.append(data)
# print ("recording stopped")
stream.stop_stream()
stream.close()
audio.terminate()
waveFile = wave.open(WAVE_OUTPUT_FILENAME1, 'wb')
waveFile.setnchannels(CHANNELS)
waveFile.setsampwidth(audio.get_sample_size(FORMAT))
waveFile.setframerate(RATE)
waveFile.writeframes(b''.join(Recordframes))
waveFile2 = wave.open(WAVE_OUTPUT_FILENAME2, 'wb')
waveFile2.setnchannels(CHANNELS)
waveFile2.setsampwidth(audio.get_sample_size(FORMAT))
waveFile2.setframerate(RATE)
waveFile2.writeframes(b''.join(Recordframes2))
waveFile.close()
waveFile2.close()

Answer 1

You can use AVAudioEngine (link) to tap into the raw audio data. Alternatively, still using AVAudioEngine, you could add an AVAudioUnitEQ (link) node to your audio graph and use that boost the gain.
Using either method, you can then write out to a file using AVAudioFile (link).