通过HTTP直播流从MP3提取ID3标签 [英] Extracting ID3 tags from MP3 over HTTP Live Streaming

问题描述

我从一个困难的时间提取ID3信息从通过Live HTTP Streaming流式传输的MP3（使用Wowza媒体服务器，如果有人好奇）。我知道标签（现在的相册标签和专辑的艺术品标签）正在适当地嵌入每个文件段，因为当我手动下载它们可以看到他们在每个段中列出的 .m3u 由服务器生成的索引文件。

I've been having quite a difficult time extracting ID3 information from an MP3 being streamed over Live HTTP Streaming (using the Wowza media server, if anyone is curious). I know that the tags (right now the album tag and the album artwork tag) are being properly embedded in each of the file segments because when I download them manually I can see them in each segment as listed in the .m3u index file generated by the server.

我使用 AVFoundation 这样，我就这样设置：

I am using the AVFoundation classes to do this, and I have it setup as such:

- (void)initializeAudioStream {
    NSURL *streamUrl = [NSURL URLWithString:self.urlField.text];
    AVPlayerItem *playerItem = [AVPlayerItem playerItemWithURL:streamUrl];
    self.musicPlayer = [AVPlayer playerWithPlayerItem:playerItem];
    self.musicPlayer.actionAtItemEnd = AVPlayerActionAtItemEndNone;
    [self.musicPlayer addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:NULL];
}

一旦我的KVO方法被触发，我开始玩 self.musicPlayer ，我调用 addPeriodicTimeObserverForInterval 每1/4秒。正是在这种方法，我试图提取ID3元数据。

Once my KVO method is triggered, I start playing self.musicPlayer and I call addPeriodicTimeObserverForInterval on it for each 1/4 second. It is in this method that I try to extract the ID3 metadata.

我已经尝试了一切我可以想到的事情，以实现这一点，包括打印出

I have tried everything I can think of on the iOS side of things to accomplish this, including printing out

self.musicPlayer.currentItem.asset.commonMetadata

，并且迭代每个 AVAssetTrack 实例并打印出它们的元数据。 p>

as well as iterating over each of the AVAssetTrack instances and printing out their metadata.

for (AVAssetTrack *track in self.musicPlayer.currentItem.asset.tracks) {
    NSLog(@"Media type of track: %@", track.mediaType);
    NSLog(@"Track metadata: %@", track.commonMetadata);
}

有趣的是，资产总是说它有2个音轨。当我打印出他们的 mediaType 属性，我得到soun的第一个和tmet的第二个。我的假设是，第一轨道是音频数据本身，第二轨道是元数据。但是，我只看到一个空数组在 commonMetadata 。

What's interesting is that the asset always says it has 2 tracks. When I print out their mediaType property I get "soun" for the first one and "tmet" for the second. My assumption is that the first track is the audio data itself and the second track is metadata. However, I only ever see an empty array in commonMetadata.

我也检查属性的状态使用 statusOfValueForKey：error ，并且 commonMetadata 键总是以 AVKeyValueStatusLoaded 。

I also check the status of the properties using statusOfValueForKey:error on the tracks, and the commonMetadata key always comes back as AVKeyValueStatusLoaded.

任何想法？我在这里完全失去了。

Any ideas? I'm at a complete loss here.

此外，我目前正在运行这个通过运行iOS 4.2.1的iPhone 4模拟器。

Also, I am currently running this through the iPhone 4 simulator running iOS 4.2.1. I can't yet put it on a device since Apple is still approving my company's developer account.

推荐答案

我不能使用<$您可能希望尝试在 AVPlayerItem 上使用 timedMetadata ： / p>

Instead of using commonMetadata you might want to try using timedMetadata on the AVPlayerItem:

[playerItem addObserver:self forKeyPath:@"timedMetadata" options:NSKeyValueObservingOptionNew context:NULL];

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