Assign default file extension based on audio format

[jbaudanza]

I am using this library to record ogg/opus files, however, the default file name was always "sound.mp4" or "sound.m4a", regardless of the audio format.

To fix this, I tried passing in a custom path to startRecord, with the correct file extension, however a native extension is required to get the proper path to the cache directory on Android.

Since a native modification is required anyway, I decided to modify this module to just pick a reasonable default file extension for the giving audio format.

I also added the proper OGG / OPUS types for Android to index.ts. These types are supported as of apiVersion 29.

[hyochan]

commas in comments could be identical here!

[jbaudanza]

I removed the commas for consistency. Let me know if you'd like to make any other adjustments.

[hyochan]

Thank you for the PR. Could you kindly review the code review suggested by GPT?

Improvement Suggestions

avFormat(fromString:)

1. Default Value Return: The current implementation returns kAudioFormatAppleLossless when the encoding value is nil. It might be better to determine the default value externally or pass it as a parameter to this function.
2. Error Handling: The function currently returns nil for unmatched strings. Adding exception handling to provide clear error messages would be beneficial.

private func avFormat(fromString encoding: String?) -> AudioFormatID? {
    guard let encoding = encoding else {
        return kAudioFormatAppleLossless
    }

    switch encoding {
    case "lpcm":
        return kAudioFormatAppleIMA4
    case "ima4":
        return kAudioFormatAppleIMA4
    case "aac":
        return kAudioFormatMPEG4AAC
    case "MAC3":
        return kAudioFormatMACE3
    case "MAC6":
        return kAudioFormatMACE6
    case "ulaw":
        return kAudioFormatULaw
    case "alaw":
        return kAudioFormatALaw
    case "mp1":
        return kAudioFormatMPEGLayer1
    case "mp2":
        return kAudioFormatMPEGLayer2
    case "mp4":
        return kAudioFormatMPEG4AAC
    case "alac":
        return kAudioFormatAppleLossless
    case "amr":
        return kAudioFormatAMR
    case "flac":
        if #available(iOS 11.0, *) {
            return kAudioFormatFLAC
        }
    case "opus":
        return kAudioFormatOpus
    case "wav":
        return kAudioFormatLinearPCM
    default:
        return nil
    }
}

fileExtension(forAudioFormat:)

1. Error Handling: For unsupported AudioFormatID, the current implementation returns "audio" as a default value. It would be better to provide clear error messages.
2. Documentation: Adding comments explaining each AudioFormatID in the code would make it easier to understand.

private func fileExtension(forAudioFormat format: AudioFormatID) -> String {
    switch format {
    case kAudioFormatOpus:
        return "ogg"
    case kAudioFormatLinearPCM:
        return "wav"
    case kAudioFormatAC3, kAudioFormat60958AC3:
        return "ac3"
    case kAudioFormatAppleIMA4:
        return "caf"
    case kAudioFormatMPEG4AAC, kAudioFormatMPEG4CELP, kAudioFormatMPEG4HVXC, kAudioFormatMPEG4TwinVQ, kAudioFormatMPEG4AAC_HE, kAudioFormatMPEG4AAC_LD, kAudioFormatMPEG4AAC_ELD, kAudioFormatMPEG4AAC_ELD_SBR, kAudioFormatMPEG4AAC_ELD_V2, kAudioFormatMPEG4AAC_HE_V2, kAudioFormatMPEG4AAC_Spatial:
        return "m4a"
    case kAudioFormatMACE3, kAudioFormatMACE6:
        return "caf"
    case kAudioFormatULaw, kAudioFormatALaw:
        return "wav"
    case kAudioFormatQDesign, kAudioFormatQDesign2:
        return "mov"
    case kAudioFormatQUALCOMM:
        return "qcp"
    case kAudioFormatMPEGLayer1:
        return "mp1"
    case kAudioFormatMPEGLayer2:
        return "mp2"
    case kAudioFormatMPEGLayer3:
        return "mp3"
    case kAudioFormatMIDIStream:
        return "mid"
    case kAudioFormatAppleLossless:
        return "m4a"
    case kAudioFormatAMR:
        return "amr"
    case kAudioFormatAMR_WB:
        return "awb"
    case kAudioFormatAudible:
        return "aa"
    case kAudioFormatiLBC:
        return "ilbc"
    case kAudioFormatDVIIntelIMA, kAudioFormatMicrosoftGSM:
        return "wav"
    default:
        return "audio"
    }
}

[jbaudanza]

1. Default Value Return: The current implementation returns kAudioFormatAppleLossless when the encoding value is nil. It might be better to determine the default value externally or pass it as a parameter to this function.

If the encoding value is unrecognized, I think the library should raise an error, rather than falling back to a default. This behavior would be more expected and less surprising to a consumer of this module.

btw, I think kAudioFormatMPEG4AAC would be a better choice of default format, rather than kAudioFormatAppleLossless, but I didn't want to address that in this PR.

2. Error Handling: The function currently returns nil for unmatched strings. Adding exception handling to provide clear error messages would be beneficial.

The calling function startRecorder will indeed return a rejected promise to the caller if avFormat returns nil.

1. Error Handling: For unsupported AudioFormatID, the current implementation returns "audio" as a default value. It would be better to provide clear error messages.

These formats are not necessarily "unsupported", but are traditionally not written to a file. If, for some reason, the caller wants to write these a file, I think .audio is a reasonable choice for a file extension.

2. Documentation: Adding comments explaining each AudioFormatID in the code would make it easier to understand.

I think the constant names are descriptive enough without adding more comments. More details are available in the Apple documentation: https://developer.apple.com/documentation/coreaudiotypes/1572096-audio_format_identifiers

[hyochan]

Thank you for the prompt and kind review response. I'll go ahead and merge it!