帮助在 Cocoa 和 iOS 应用中创建 MPEG-1 Layer 2 (.mp2) 音频文件。

用法

TWLEncoder 与在 iOS 7 中介绍的 NSURLSession 库的工作方式类似。您使用配置编码器，并使用它创建和运行任务。关于编码器及其任务的信息通过委托进行通信。幕后场景，任务在操作队列中处理。

MP2 音频的主要用途之一是美国的公共广播系统。TWLEncoder附带了一个基本配置，应适用于大多数系统。您可以在使用之前自定义该配置，或从头开始构建配置以满足您的需求。

构建编码器

TWLEncoderConfiguration *config = TWLEncoderConfiguration.publicRadioConfiguration;
TWLEncoder *encoder = [TWLEncoder encoderWithConfiguration:config delegate:self operationQueue:nil];

创建任务

NSURL *fileURL = [NSURL fileURLWithPath:@"~/Desktop/master-2014_02_19-b.wav"];
TWLEncoderTask *task = [encoder taskWithURL:fileURL];
[task resume]; // Tasks start suspended and must be resumed to begin

委托

- (void)encoder:(TWLEncoder *)encoder task:(TWLEncoderTask *)task didWriteFrames:(int64_t)framesWritten totalFramesWritten:(int64_t)totalFramesWritten totalFrameExpectedToWrite:(int64_t)totalFramesExpectedToWrite bytesWritten:(int64_t)bytessWritten totalBytesWritten:(int64_t)totalBytesWritten {
  // eg Update a progress bar in the UI
}

- (void)encoder:(TWLEncoder *)encoder task:(TWLEncoderTask *)task didFinishEncodingToURL:(NSURL *)location {
  // eg Copy the encoded file to a permanent location
  // The temporary file that the encoding was written to will be removed as soon
  // as this method returns, so you must read or relocate the data before then.
}