@voicethread/nativescript-transcoder

Nativescript Transcoder

This plugin provides a few audio/video transcoding functions for Android API 21+ and iOS 4+.

transcode allows you to transcode an input video/audio file to a specified height/width and produces an Mp4 file with H264 video and AAC audio encoding. iOS also supports modifying the video frame rate along with some audio settings.

mergeMp4Files will merge a series of Mp4 files to produce a single Mp4 file from all input Mp4 files provided. For iOS, this function currently requires that all mp4 input files have audio and video tracks.

For Android, convertAudioToMp4 will convert natively supported audio files to produce an Mp4 with AAC audio encoding.

For both Android and iOS, all function outputs will be saved as an Mp4 file using h264 and AAC encoding.

Installation

npm install @voicethread/nativescript-transcoder --save

OR

ns plugin add @voicethread/nativescript-transcoder

Basic Usage

The best way to understand how to use the plugin is to study the demo app included in this repo. You can see how the plugin is used in a TypeScript application by looking at apps/demo/src/plugin-demos/nativescript-transcoder-basic.ts.

1. Import the plugin.

import { NativescriptTranscoder } from '@voicethread/nativescript-transcoder';

2. Transcode a video to a specific height and/or width (the example below uses a filepicker, but you can use a video recording file from the camera or another source)

selectAndTranscodeVideo(): void {
  // input
  const inputFile = await filePicker(MediaType.VIDEO, false)?.[0];

  // output
   const outputPath = knownFolders.documents().getFile('transcoded-video.mp4').path;
    if (File.exists(outputPath)) {
      const file = File.fromPath(outputPath);
      // make sure file specified as the output path doesn't exist before starting the transcoding process
      file.removeSync();
    }
    const transcoder = new NativescriptTranscoder();
    transcoder
      .transcode(
        inputFile.path,
        outputPath,
          {
               height: 720,                
              //width: 1080,  //you can also set specific width, both or neither
          }
      ).then(transcodedFile => {
        // do something with the transcoded file
      })

}

Events

The following events are emitted during the transcoding process:

• TRANSCODING_STARTED - emitted at the beginning of the transcoding process
• TRANSCODING_PROGRESS - emitted over time with the percentage (0 to 1) completed
• TRANSCODING_COMPLETE - emitted after a successful transcoding process (the transcode function will return the transcoded file)
• TRANSCODING_ERROR - emitted when the transcoding process emits an error (the transcode function will return a rejected promise at this point)

You can listen to these events by attaching the on listener to the transcoder

  const transcoder = new NativescriptTranscoder()
  transcoder.on(NativescriptTranscoder.TRANSCODING_PROGRESS, (payload: MessageData) => {
      // for iOS  you'll have to wrap any UI updates in `executeOnMainThread` as the events are emitted from a different thread
      executeOnMainThread(() => {
        progressBar.value = payload.data.progress * 100;
      });
    });

Options

export interface VideoConfig {  
  height?: number;
  width?: number;
  force?: boolean; // force transcoding to allow transcoding to the same or higher quality
  frameRate?: number; // iOS only
  audioChannels?: number; // iOS only
  audioSampleRate?: number; // iOS only
  audioBitRate?: number; // iOS only
}

Utilities

The transcoder plugin provides the following functions for working with Mp4 files:

Troubleshooting

Logs are turned off by default. If you want to view the logs as the video is being processed, you can turn them on by setting the log level to verbose before starting the transcode process.

startTranscoding(): void {
  const transcdoer = new NativescriptTranscoder();
  transcoder.setLogLevel('verbose');
  transcoder.transcode(...);
}

Note: not all video/audio codecs/formats are supported, so the transcode may fail. This is particularly true on Android, where the device and OS version dictate what is actually supported.

Acknowledgements

This plugin is based on react-native-transcode for iOS. For Android, this uses the AndroidX Media3 Transformer libraries

License

Apache License Version 2.0