app付费视频30秒试看开发技术

在App开发中，实现付费视频功能是一个非常常见的需求，其中又会有很多用户希望能够提供30秒的试看时间，以便更好的决定是否进行购买。

下面我们来介绍一下实现这个功能的原理和方法。具体实现方式分为两种：客户端实现和服务器实现。

一、 客户端实现

1.客户端控制播放时间

客户端可以通过设置一个时间段，比如说30秒，然后在这个时间到达时暂停播放，等待用户操作去选择是否购买。

如下示例代码：

```

//设置一个30秒的定时器，时间到了暂停播放

CGRect videoViewFrame = CGRectMake(0, 0, self.view.frame.size.width, 200);

AVPlayerItem *playerItem = [[AVPlayerItem alloc] initWithURL:[NSURL URLWithString:@"http://example.com/video.mp4"]];

AVPlayer *player = [[AVPlayer alloc] initWithPlayerItem: playerItem];

//设置定时器时间为30秒

[player addPeriodicTimeObserverForInterval:CMTimeMakeWithSeconds(30, NSEC_PER_SEC) queue:nil usingBlock:^(CMTime time) {

//定时器时间到，暂停播放

[player pause];

}];

AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer: player];

playerLayer.frame = videoViewFrame;

[self.view.layer addSublayer: playerLayer];

[player play];

```

2.播放前缓存

在客户端播放视频之前，先缓存一定量的视频数据，同时控制播放进度和缓存进度的比例，当播放时间达到30秒时，则停止播放，并提示用户可以付费购买。此种方式需要做大量的本地缓存处理，对于流量比较高的视频来说显得有些低效。

如下示例代码：

```

//计算需要缓存的视频时长

NSUInteger duration = 30;

NSRange range = NSMakeRange(0, duration); //需要缓存的时长范围

AVPlayerItem *playerItem = [[AVPlayerItem alloc] initWithURL: [NSURL URLWithString: @"http://example.com/video.mp4"]];

AVAsset *asset = playerItem.asset;

AVAssetResourceLoader *resourceLoader = asset.resourceLoader;

AVURLAsset *urlAsset = (AVURLAsset *)asset;

NSURLComponents *components = [NSURLComponents componentsWithURL: [urlAsset.URL absoluteURL] resolvingAgainstBaseURL: NO];

components.scheme = @"custom";

//获取缓存区域的数据并存储到本地文件中

AVAssetResourceLoader *resourceLoader = asset.resourceLoader;

[resourceLoader setDelegate: self queue: dispatch_get_main_queue()];

__weak typeof(self) weakSelf = self;

self.resourceLoaderDelegate = [ResourceLoaderDelegate new];

[self.resourceLoaderDelegate addCompletionHandler: ^BOOL(NSData *data, NSError *__autoreleasing *error) {

BOOL success = NO;

if (range.length > 0 && self.requestTask) {

if (resourceLoader.localCachePath.length > 0) {

success = YES;

}

}

return success;

} forRequestTask: self.requestTask];

//计算缓存时长

int length = 1;

NSURL *customSchemeURL = [components URL];

AVURLAsset *urlAsset = [[AVURLAsset alloc] initWithURL: customSchemeURL options: nil];

NSArray *keys = @[@"duration"];

[urlAsset loadValuesAsynchronouslyForKeys:keys completionHandler:^{

NSError *error = nil;

AVKeyValueStatus durationStatus = [urlAsset statusOfValueForKey:@"duration" error:&error];

switch (durationStatus) {

case AVKeyValueStatusLoaded:

dispatch_async(dispatch_get_global_queue(0, DISPATCH_QUEUE_PRIORITY_DEFAULT), ^{

//1.计算需要缓存的数据字节

unsigned long long offset = range.location;

unsigned long long length = range.length;

//2.向服务端请求需要缓存的数据

NSData *requestData = [self sendRequestWithOffset: offset length: length];

if (requestData) {

//3.将请求来的数据存储到本地缓存文件中

BOOL result = [self writeData: requestData atOffset:offset];

if (result) {

//异步回调

dispatch_async(dispatch_get_main_queue(), ^{

[urlAsset.resourceLoader setDelegate:nil queue: NULL];

//创建播放器

weakSelf.playerItem = [[AVPlayerItem alloc] initWithURL: [NSURL URLWithString: @"http://example.com/video.mp4"]];

weakSelf.player = [AVPlayer playerWithPlayerItem:weakSelf.playerItem];

weakSelf.playerLayer = [AVPlayerLayer playerLayerWithPlayer:weakSelf.player];

weakSelf.playerLayer.frame = CGRectMake(0, 0, weakSelf.view.frame.size.width, 200);

[weakSelf.view.layer addSublayer: weakSelf.playerLayer];

[weakSelf.player play];

});

}

}

});

break;

default:

break;

}

}];

```

二、服务器实现

1.前端只需调用API

在服务器实现的方式中，前端只需调用服务端提供的API，即可在客户端以流的方式播放视频内容。在API中，可以设置视频内容试看的时间长度为30秒，超过30秒部分的内容需要付费才可以继续观看。

如下示例代码：

```

//前端根据用户ID和视频ID向API发起请求获取播放URL

NSString *userId = @"user-123456";

NSString *videoId = @"video-123456";

NSString *urlStr = [NSString stringWithFormat:@"api/v1/playUrl?userId=%@&videoId=%@", userId, videoId];

NSURLSession *session = [NSURLSession sharedSession];

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlStr]];

[request setHTTPMethod:@"GET"];

NSURLSessionDataTask *task = [session dataTaskWithRequest:request

completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {

if(error) {

//请求出现错误，处理异常

}else {

//解析返回结果

NSDictionary *result = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];

NSString *playUrl = result[@"playUrl"];

//根据返回的URL展示视频播放器

AVPlayer *player = [[AVPlayer alloc] initWithURL:[NSURL URLWithString:playUrl]];

AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:player];

playerLayer.frame = CGRectMake(0, 0, self.view.width, 200);

[self.view.layer addSublayer:playerLayer];

[player play];

}

}];

[task resume];

//api/v1/playUrl接口的实现,服务端根据用户ID和视频ID获取播放URL

public String getPlayUrl(String userId, String videoId) {

//1.根据用户ID和视频ID获取对应的视频信息

Video video = videoMapper.getVideoInfo(userId, videoId);

if(video == null) {

throw new BusinessException("该视频不存在！");

}

//2.检查该用户是否已经购买了该视频

boolean buyed = userService.checkUserBuyedVideo(userId, videoId);

if(buyed) {

//已购买，返回完整播放URL

return video.getUrl();

}else {

//未购买，返回试看URL（试看时间为30秒）

return video.getTrialUrl();

}

}

```

2.服务端自动截取前30秒

另外，服务端也可以通过自动截取视频前30秒，来实现视频试看功能。具体实现原理与上述两种方式类似。

如下示例代码：

```

//客户端请求服务端播放视频

NSString *userId = @"user-123456";

NSString *videoId = @"video-123456";

NSString *urlStr = [NSString stringWithFormat:@"api/v1/playUrl?userId=%@&videoId=%@", userId, videoId];

NSURLSession *session = [NSURLSession sharedSession];

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlStr]];

[request setHTTPMethod:@"GET"];

NSURLSessionDataTask *task = [session dataTaskWithRequest:request

completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {

if(error) {

//请求出现错误，处理异常

}else {

//解析返回结果

NSDictionary *result = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];

NSString *playUrl = result[@"playUrl"];

//根据返回的URL展示视频播放器

AVPlayer *player = [[AVPlayer alloc] initWithURL:[NSURL URLWithString:playUrl]];

AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:player];

playerLayer.frame = CGRectMake(0, 0, self.view.width, 200);

[self.view.layer addSublayer:playerLayer];

[player play];

}

}];

[task resume];

//api/v1/playUrl接口截取前30秒的实现

public String getPlayUrl(String userId, String videoId) {

//1.根据用户ID和视频ID获取对应的视频信息

Video video = videoMapper.getVideoInfo(userId, videoId);

if(video == null) {

throw new BusinessException("该视频不存在！");

}

//2.检查该用户是否已经购买了该视频

boolean buyed = userService.checkUserBuyedVideo(userId, videoId);

if(buyed) {

//已购买完整视频，返回完整播放URL

return video.getUrl();

}else {

//未购买，返回截取前30秒试看，并给出购买提示

//先获取完整视频URL

String fullVideoUrl = video.getUrl();

//调用接口截取视频前30秒，并获取新的URL

String trialUrl = videoService.cutVideoToUrl(fullVideoUrl, 0, 30);

return trialUrl;

}

}

//VideoService中截取视频前30秒的实现

public String cutVideoToUrl(String videoUrl, int startSecond, int endSecond) {

FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(videoUrl);

try {

grabber.start();

if(startSecond >= grabber.getLengthInTime()/1000000) {

throw new BusinessException("截取起始时间不能超过总时长！");

}

FFmpegFrameRecorder recorder = new FFmpegFrameRecorder("out.mp4", grabber.getImageWidth(), grabber.getImageHeight(), grabber.getAudioChannels());

recorder.setVideoCodec(avcodec.AV_CODEC_ID_MPEG4);

recorder.setFormat("mp4");

recorder.setFrameRate(grabber.getFrameRate());

recorder.setSampleRate(grabber.getSampleRate());

recorder.setAudioChannels(grabber.getAudioChannels());

recorder.start();

long start = startSecond * 1000000;

long end = endSecond * 1000000;

Frame frame = null;

while((frame = grabber.grab()) != null) {

if(frame.timestamp > start && frame.timestamp <= end) { //在截取的范围内

recorder.record(frame);

}

if(frame.timestamp > end) { //超出截取范围

break;

}

}

grabber.stop();

grabber.release();

recorder.stop();

recorder.release();

return "http://example.com/out.mp4";

} catch (Exception e) {

throw new BusinessException("截取视频失败！");

}

}

```

综上所述，客户端实现和服务端实现都可以实现给用户提供30秒试看的功能，实现的方式各不相同，具体实现方案应根据实际情况来选择。