react-native using expo-av IOS mp4 file openai's audio transcriptions invalid file format

Question

I'm getting this back error message back from openai's transcription endpoint

message: "Invalid file format. Supported formats: ['m4a', 'mp3', 'webm', 'mp4', 'mpga', 'wav', 'mpeg']"

Here is my code:

// needed for IoS
if (audioPermission) {
  await Audio.setAudioModeAsync({
    allowsRecordingIOS: true,
    playsInSilentModeIOS: true,
  });
}
Audio.IOSOutputFormat;
const newRecording = new Audio.Recording();

const recordingOptions = {
  ios: {
    extension: '.mp4', // Specify the audio file extension,
    audioQuality: Audio.RECORDING_OPTION_IOS_AUDIO_QUALITY_HIGH, // Specify the audio quality
  },
  android: {
    extension: '.mp4', // Specify the audio file extension,
  },
};
console.log('Starting Recording');
await newRecording.prepareToRecordAsync(recordingOptions);

await newRecording.startAsync();

console.log('Stopping recording..');
await recording.stopAndUnloadAsync();
const recordingUri = recording.getURI();
console.log('Recording stopped and stored at URI', recordingUri);
console.log('OPENAI_API_KEY', OPENAI_API_KEY);
// Create a file name for the new MP4 recording
const fileName = `recording-${Date.now()}.mp4`;

// Calls openai translations endpoint
try {
  const url = 'https://api.openai.com/v1/audio/transcriptions';
  const headers = {
    Authorization: `Bearer ${OPENAI_API_KEY}`,
    'Content-Type': 'multipart/form-data',
  };

  const fileData = await FileSystem.readAsStringAsync(recordingUri, {
    encoding: FileSystem.EncodingType.Base64,
  });
  const fileObject = new File([fileData], fileName, {
    type: 'audio/mp4',
  });

  const formData = new FormData();
  formData.append('file', fileObject, fileName);
  formData.append('model', 'whisper-1');

  axios
    .post(url, formData, { headers })
    .then((response) => {
      console.log('Transcription response:', response.data);
    })
    .catch((error) => {
      console.error('Error:', error);
    });
} catch (error) {
  console.error(error);
}

My situation is very similar to this stackoverflow question, however that implementation crashes without even calling the api endpoint. Tried using chatgpt and still couldn't find a solution yet.