Audio format for iOS and Android

Question

Sorry if I am asking too generic question.

We are in the process of developing an application which records and plays audio on mobile devices. This application is be

Answer 1

Android and iOS use the same server to storage records. All records are saved without any extension.

When Android downloads a record from the server, my app adds an ".aac" extension.
When using iOS, it adds an ".m4a" extension.

The same record plays good on both mobile platforms.

Record on iOS:

NSDictionary recorderSettings = [[NSDictionary alloc] initWithObjectsAndKeys:
                        [NSNumber numberWithInt:kAudioFormatMPEG4AAC], AVFormatIDKey,
                        [NSNumber numberWithInt:16000],AVSampleRateKey,
                        [NSNumber numberWithInt:1],AVNumberOfChannelsKey,
                        [NSNumber numberWithInt:16],AVLinearPCMBitDepthKey,
                        [NSNumber numberWithBool:NO],AVLinearPCMIsBigEndianKey,
                        [NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey,
                        nil];

For Android:

myRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
myRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
myRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
myRecorder.setAudioSamplingRate(16000);
myRecorder.setAudioChannels(1);
mRecorder.setOutputFile(fileName);