iOS中關於流媒體的簡介：介於下載本地播放與實時流媒體之間的一種播放形式，下載本地播放必須全部將文件下載完成後才能播放，而漸進式下載不必等到全部下載完成後再播放，它可以一邊下載一邊播放，在完成播放內容之後，整個文件會保存在手機上。

實時流媒體

實時流媒體是一邊接收數據包一邊播放，本地不保留文件副本，實時流式傳輸總是實時傳送，可以實時實況轉播，支持隨機訪問，用戶可以快進或者快退以觀看前面或後面的內容。實時流媒體傳輸必須保證數據包的傳輸速度大於文件的播放速度，否則用戶看到的視頻會出現暫停。當網絡堵塞情況下視頻質量會下降，所以要想保證視頻的質量漸進式下載會更好一些。

下面是本人親測的流媒體播放和下載教程：

1.界面搭建（如圖）

2.用到的第三方助手類

下載地址：http://pan.baidu.com/s/1hrvqXA8

3.開始項目－頭文件及相關宏

LO_ViewController.h

#import 
#import 
#import "M3U8Handler.h"
#import "VideoDownloader.h"
#import "HTTPServer.h"

@interface LO_ViewController : UIViewController

@property (nonatomic, strong)HTTPServer * httpServer;
@property (nonatomic, strong)VideoDownloader *downloader;

@end

LO_ViewController.m

#import "LO_ViewController.h"

@interface LO_ViewController ()

@property (weak, nonatomic) IBOutlet UIProgressView *progressView;

@property (weak, nonatomic) IBOutlet UILabel *progressLabel;

@property (weak, nonatomic) IBOutlet UIButton *downloadButton;

@property (weak, nonatomic) IBOutlet UIButton *clearButton;

@end

@implementation LO_ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    
    //打開本地服務器
    [self openHttpServer];
    
    if ([[[NSUserDefaults standardUserDefaults] objectForKey:@"isDownload"] boolValue]) {
        [self.downloadButton setTitle:@"已完成" forState:UIControlStateNormal];
        self.downloadButton.enabled = NO;
        self.clearButton.enabled = YES;
        M3U8Handler *handler = [[M3U8Handler alloc] init];
        [handler praseUrl:[NSString stringWithFormat:@"http://v.youku.com/player/getM3U8/vid/XNjUxMTE4NDAw/type/mp4"]];
        handler.playlist.uuid = @"XNjUxMTE4NDAw";
        self.downloader = [[VideoDownloader alloc]initWithM3U8List:handler.playlist];
        [self.downloader addObserver:self forKeyPath:@"clearCaches" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil]; // 判斷是否清理緩存
    }
    
    
}

#pragma mark - 打開本地服務器

- (void)openHttpServer
{
    self.httpServer = [[HTTPServer alloc] init];
    [self.httpServer setType:@"_http._tcp."];  // 設置服務類型
    [self.httpServer setPort:12345]; // 設置服務器端口
        
    // 獲取本地Library/Cache路徑下downloads路徑
    NSString *webPath = [kLibraryCache stringByAppendingPathComponent:kPathDownload];
    NSLog(@"-------------\nSetting document root: %@\n", webPath);
	
    // 設置服務器路徑
	[self.httpServer setDocumentRoot:webPath];
    NSError *error;
    
	if(![self.httpServer start:&error])
	{
        NSLog(@"-------------\nError starting HTTP Server: %@\n", error);
	}
}

#pragma mark - 清理緩存
- (IBAction)clearCaches:(id)sender {
    [self.downloader cleanDownloadFiles];
}

#pragma mark - 在線流媒體播放

- (IBAction)playStreamingMedia:(id)sender {
    
    // 優酷視頻m3u8新地址格式如下:http://pl.youku.com/playlist/m3u8?vid=XNjUxMTE4NDAw&type=mp4
    // 如果上面的鏈接不可用，那麼使用這個鏈接http://v.youku.com/player/getM3U8/vid/XNjUxMTE4NDAw/type/mp4，如果兩個連接都不可以用的話，那麼很大可能是優酷的服務器掛掉了
    // 如果上面的兩種格式都不行的話，考慮用這個格式，當然如果這個格式不行的話，是上面的，或者直接換個對應的m3u8的地址 http://pl.youku.com/playlist/m3u8?vid=162779600&ts=1407469897&ctype=12&token=3357&keyframe=1&sid=640746989782612d6cc70&ev=1&type=mp4&ep=dCaUHU2LX8YJ4ivdjj8bMyqxJ3APXP8M9BiCiNRiANQnS%2B24&oip=2043219268
    NSURL *url = [[NSURL alloc] initWithString:@"http://pl.youku.com/playlist/m3u8?vid=162779600&ts=1407469897&ctype=12&token=3357&keyframe=1&sid=640746989782612d6cc70&ev=1&type=flv&ep=dCaUHU2LX8YJ4ivdjj8bMyqxJ3APXP8M9BiCiNRiANQnS%2B24&oip=2043219268"];
    MPMoviePlayerViewController *player = [[MPMoviePlayerViewController alloc] initWithContentURL:url];
    
    [self presentMoviePlayerViewControllerAnimated:player];
    
}

#pragma mark - 視頻下載

- (IBAction)downloadStreamingMedia:(id)sender {
    
    UIButton *downloadButton = sender;
    
    // 獲取本地Library/Cache路徑
    NSString *localDownloadsPath = [kLibraryCache stringByAppendingPathComponent:kPathDownload];
    // 獲取視頻本地路徑
    NSString *filePath = [localDownloadsPath stringByAppendingPathComponent:@"XNjUxMTE4NDAw/movie.m3u8"];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    
    // 判斷視頻是否緩存完成，如果完成則播放本地緩存
    if ([fileManager fileExistsAtPath:filePath]) {
        [downloadButton setTitle:@"已完成" forState:UIControlStateNormal];
        downloadButton.enabled = NO;
    
    }else{
        M3U8Handler *handler = [[M3U8Handler alloc] init];
        handler.delegate = self;
        // 解析m3u8視頻地址
        [handler praseUrl:@"http://pl.youku.com/playlist/m3u8?vid=162779600&ts=1407469897&ctype=12&token=3357&keyframe=1&sid=640746989782612d6cc70&ev=1&type=flv&ep=dCaUHU2LX8YJ4ivdjj8bMyqxJ3APXP8M9BiCiNRiANQnS%2B24&oip=2043219268"];
        
        // 開啟網絡指示器
        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
    }
}

#pragma mark - 播放本地緩存視頻

- (IBAction)playVideoFromLocal:(id)sender {
    
    NSString * playurl = [NSString stringWithFormat:@"http://127.0.0.1:12345/XNjUxMTE4NDAw/movie.m3u8"];
    NSLog(@"本地視頻地址-----%@", playurl);
    
    // 獲取本地Library/Cache路徑
    NSString *localDownloadsPath = [kLibraryCache stringByAppendingPathComponent:kPathDownload];
    // 獲取視頻本地路徑
    NSString *filePath = [localDownloadsPath stringByAppendingPathComponent:@"XNjUxMTE4NDAw/movie.m3u8"];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    
    // 判斷視頻是否緩存完成，如果完成則播放本地緩存
    if ([fileManager fileExistsAtPath:filePath]) {
        MPMoviePlayerViewController *playerViewController =[[MPMoviePlayerViewController alloc]initWithContentURL:[NSURL URLWithString: playurl]];
        [self presentMoviePlayerViewControllerAnimated:playerViewController];
    }
    else{
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Sorry" message:@"當前視頻未緩存" delegate:self cancelButtonTitle:@"確定" otherButtonTitles:nil, nil];
        [alertView show];
    }
}

#pragma mark -
#pragma mark - 視頻解析完成
-(void)praseM3U8Finished:(M3U8Handler*)handler
{
    handler.playlist.uuid = @"XNjUxMTE4NDAw";
    self.downloader = [[VideoDownloader alloc]initWithM3U8List:handler.playlist];
    [self.downloader addObserver:self forKeyPath:@"currentProgress" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil]; // 設置觀察者用來得到當前下載的進度
    [self.downloader addObserver:self forKeyPath:@"clearCaches" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil]; // 判斷是否清理緩存
    self.downloader.delegate = self;
    [self.downloader startDownloadVideo]; // 開始下載
}

#pragma mark - 通過觀察者監控下載進度顯示/緩存清理

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqualToString:@"clearCaches"]) {
        self.downloadButton.enabled = YES;
        [self.downloadButton setTitle:@"下載" forState:UIControlStateNormal];
        self.clearButton.enabled = NO;
        [[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithBool:NO] forKey:@"isDownload"];
        [[NSUserDefaults standardUserDefaults] synchronize];
        self.progressView.progress = 0.0;
        self.progressLabel.text = [NSString stringWithFormat:@"%.2f%%", 0.0];
    }else{
        self.progressLabel.text = [NSString stringWithFormat:@"%.2f%%", 100 * [[change objectForKey:@"new"] floatValue]];
        self.progressView.progress = [[change objectForKey:@"new"] floatValue];
        if (self.progressView.progress == 1) {
            [[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithBool:YES] forKey:@"isDownload"];
            [self.downloadButton setTitle:@"已完成" forState:UIControlStateNormal];
            [[NSUserDefaults standardUserDefaults] synchronize];
            self.clearButton.enabled = YES;
            self.downloadButton.enabled = NO;
        }
    }
    
}

#pragma mark - 視頻解析失敗
-(void)praseM3U8Failed:(M3U8Handler*)handler
{
    NSLog(@"視頻解析失敗-failed -- %@",handler);
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"噢,NO~