Record audio on iPhone with smallest file size

Question

I want to record audio with iPhone and then upload it to server.

I could record the audio, but my question is about which format should I use to record audio, so that the Recorder will result a file with smallest file size.

Solution 1

Here are the results for few encoding supported by iPhone. Size of audio file in KB of duration 10 sec.

kAudioFormatMPEG4AAC : 164,

kAudioFormatAppleLossless : 430,

kAudioFormatAppleIMA4 : 475,

kAudioFormatULaw : 889,

kAudioFormatALaw : 889,

Among these kAudioFormatMPEG4AAC is having smallest size.

Solution 2

Apple iOS supports playback audio in these formats:

1. AAC (MPEG-4 Advanced Audio Coding)
2. ALAC (Apple Lossless)
3. HE-AAC (MPEG-4 High Efficiency AAC)
4. iLBC (internet Low Bitrate Codec, another format for speech)
5. IMA4 (IMA/ADPCM)
6. Linear PCM (uncompressed, linear pulse code modulation)
7. MP3 (MPEG-1 audio layer 3)
8. µ-law and a-law

For recording following formats are possible:

1. AAC (MPEG-4 Advanced Audio Coding)
2. ALAC (Apple Lossless)
3. iLBC (internet Low Bitrate Codec, for speech)
4. IMA4 (IMA/ADPCM)
5. Linear PCM (uncompressed, linear pulse-code modulation)
6. µ-law and a-law

while only AAC supports hardware-assisted encoding (see Apple iOS SDK documentation)

For the universality in availability I prefer MP3.

Check these links to find exact code to record audio - Recording Audio on an iPad with AVAudioRecorder

Comments

[User97693321]

Can you please confirm that which iOS versions are supporting AMR (Adaptive Multi-rate) audio for recording and playback?

[Srikar Appalaraju]

sorry, AMP is supported for playback only.

[Admin]

Hi, thanks for your answer, but what about iLBC (internet Low Bit Rate Codec), I heard that which is the smallest file size, did you try it? Thanks.

[Oded Ben Dov]

According to the following documentation, MP3 is not supported for recording, only playing. developer.apple.com/library/ios/#documentation/AudioVideo/…

[Michael Dorner]

This list is not up to date: see supported audio formats in the Apple iOS SDK Documentation: developer.apple.com/library/ios/documentation/AudioVideo/…

[Michael Dorner]

And maybe also interesting and relevant: AAC supports hardware-assisted encoding.

[Mohamed Amer]

if i will user kAudioFormatMPEG4AAC or kAudioFormatiLBC, what is the extension type for the file when i saved it on the server ? .mp3 or what ?

[Jitendra Singh]

kAudioFormatMPEG4AAC - aac, and kAudioFormatiLBC - amr

[Mohamed Amer]

@JitendraSingh Thanks (Y)