The project demonstrates how to use Twilio's Programmable Video SDK to access raw audio samples using the TVIAudioSink API on TVIAudioTrack. Local and remote audio is recorded using AVFoundation.framework and speech is recognized using Speech.framework.
See the master README for instructions on how to generate access tokens and connect to a Room.
This example requires Xcode 9.0 and the iOS 11.0 SDK, as well as a device running iOS 10.0 or above.
Once you have setup your access token, install and run the example. You will be presented with the following screen:
After you connect to a Room tap on your camera preview to begin recognizing local audio. As you speak ExampleSpeechRecognizer will attempt to use Speech.Framework to transcribe your speech and display the text on screen. Once other Participants join you can select their video to recognize remote speech.
Audio is automatically recorded when you join a Room. After disconnecting, tap "Recordings" to browse a list of your TVIAudioTracks recorded using ExampleAudioRecorder. Select a recording cell to begin playback using AVPlayerViewController, or swipe to delete the file.
- Local audio samples are not raised until at least one underlying WebRTC PeerConnection is negotiated. In a Peer-to-Peer Room it is not possible to record or recognize audio until at least one other Participant joins. The same limitation does not apply to Group Rooms where there is a persistent PeerConnection with Twilio's media servers.
- When a
TVIAudioSinkis added to aTVIRemoteAudioTrackand encoded audio has not been received yet, the media engine outputs (1-channel / 16 kHz) silence. In order forExampleAudioRecorderto determine the correct recording format it detects and discards initial silence and waits for the first decoded samples.