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iOS视频录制、压缩导出、取帧

概述

花了点时间研究了一下常用的视频获取、录制、压缩、取帧图功能,分享给大家了!相信阅读完本篇文章,会对你有很大的帮助的!

本篇文章研究几下以个功能:

需要真机测试,才能录制视频!

效果图

iOS视频录制、压缩导出、取帧

视频录制

首先,我们弹出系统的视频录制界面,也就是UIImagePickerController控制器来实现,但是我们需要验证用户授权,只有有录制视频的权限,才能继续往下。

我们还需要判断UIImagePickerControllerSourceTypeCamera是否支持,比如模拟器就不支持,当然真机是否有不支持的并不知道,不过更安全的写法是要这么写的。视频录制可以设置录制的视频的质量,也就是分辨率的高低,通过videoQuality属性来设置。我们还可以设置录制视频的最大时长,通过videoMaximumDuration属性设置,比如这里设置为5分钟。

  // 7.0 AVAuthorizationStatus authStatus = [AVCaptureDeviceauthorizationStatusForMediaType:AVMediaTypeVideo]; if (authStatus == AVAuthorizationStatusRestricted     || authStatus == AVAuthorizationStatusDenied) {   NSLog(@"摄像头已被禁用,您可在设置应用程序中进行开启");   return; }   if ([UIImagePickerControllerisSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {   UIImagePickerController *picker = [[UIImagePickerController alloc]init];   picker.delegate = self;   picker.allowsEditing = YES;   picker.sourceType = UIImagePickerControllerSourceTypeCamera;   picker.videoQuality = UIImagePickerControllerQualityType640x480; //录像质量   picker.videoMaximumDuration = 5 * 60.0f; // 限制视频录制最多不超过5分钟   picker.mediaTypes = @[(NSString *)kUTTypeMovie];   [selfpresentViewController:pickeranimated:YEScompletion:NULL];   self.shouldAsync = YES; } else {   NSLog(@"手机不支持摄像"); }   

然后实现代理,就可以拿到录制的视频了。

从相册选择视频

从相册选择视频与弹出录制视频的代码差不多,只是sourceType不一样而已。我们一样要求先判断权限,用户是否授权,若不允许,就没有办法了。

指定sourceType为UIImagePickerControllerSourceTypeSavedPhotosAlbum就是获取保存到相册中的media。我们还要指定mediaTypes,只需要设置为kUTTypeMovie就可以了。

  AVAuthorizationStatus authStatus = [AVCaptureDeviceauthorizationStatusForMediaType:AVMediaTypeVideo]; if (authStatus == AVAuthorizationStatusRestricted     || authStatus == AVAuthorizationStatusDenied) {   NSLog(@"摄像头已被禁用,您可在设置应用程序中进行开启");   return; }   if ([UIImagePickerControllerisSourceTypeAvailable:UIImagePickerControllerSourceTypeSavedPhotosAlbum]) {   UIImagePickerController *picker = [[UIImagePickerController alloc]init];   picker.delegate = self;   picker.allowsEditing = YES;   picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;   picker.mediaTypes = @[(NSString *)kUTTypeMovie];   [selfpresentViewController:pickeranimated:YEScompletion:NULL];   self.shouldAsync = NO; } else {   NSLog(@"手机不支持摄像"); }   

同样,实现代理方法,就可以取到所选择的视频了。

保存视频到相册

写入相册可以通过ALAssetsLibrary类来实现,它提供了写入相册的API,异步写入,完成是要回到主线程更新UI:

  NSURL *videoURL = [infoobjectForKey:UIImagePickerControllerMediaURL]; ALAssetsLibrary *library = [[ALAssetsLibrary alloc]init]; dispatch_async(dispatch_get_global_queue(0, 0), ^{   // 判断相册是否兼容视频,兼容才能保存到相册   if ([libraryvideoAtPathIsCompatibleWithSavedPhotosAlbum:videoURL]) {     [librarywriteVideoAtPathToSavedPhotosAlbum:videoURLcompletionBlock:^(NSURL *assetURL, NSError *error) {       dispatch_async(dispatch_get_main_queue(), ^{         // 写入相册         if (error == nil) {             NSLog(@"写入相册成功");         } else {           NSLog(@"写入相册失败");         }       }     }];   } });   

获取视频帧图

同步获取帧图

同步获取中间帧,需要指定哪个时间点的帧,当获取到以后,返回来的图片对象是CFRetained过的,需要外面手动CGImageRelease一下,释放内存。通过AVAsset来访问具体的视频资源,然后通过AVAssetImageGenerator图片生成器来生成某个帧图片:

  // Get the video's center frame as video poster image - (UIImage *)frameImageFromVideoURL:(NSURL *)videoURL {   // result   UIImage *image = nil;      // AVAssetImageGenerator   AVAsset *asset = [AVAssetassetWithURL:videoURL];   AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc]initWithAsset:asset];   imageGenerator.appliesPreferredTrackTransform = YES;      // calculate the midpoint time of video   Float64 duration = CMTimeGetSeconds([assetduration]);   // 取某个帧的时间,参数一表示哪个时间(秒),参数二表示每秒多少帧   // 通常来说,600是一个常用的公共参数,苹果有说明:   // 24 frames per second (fps) for film, 30 fps for NTSC (used for TV in North America and   // Japan), and 25 fps for PAL (used for TV in Europe).   // Using a timescale of 600, you can exactly represent any number of frames in these systems   CMTime midpoint = CMTimeMakeWithSeconds(duration / 2.0, 600);      // get the image from   NSError *error = nil;   CMTime actualTime;   // Returns a CFRetained CGImageRef for an asset at or near the specified time.   // So we should mannully release it   CGImageRef centerFrameImage = [imageGeneratorcopyCGImageAtTime:midpoint                                                        actualTime:&actualTime                                                             error:&error];      if (centerFrameImage != NULL) {     image = [[UIImage alloc]initWithCGImage:centerFrameImage];     // Release the CFRetained image     CGImageRelease(centerFrameImage);   }      return image; }   

异步获取帧图

异步获取某个帧的图片,与同步相比,只是调用API不同,可以传多个时间点,然后计算出实际的时间并返回图片,但是返回的图片不需要我们手动再release了。有可能取不到图片,所以还需要判断是否是AVAssetImageGeneratorSucceeded,是才转换图片:

  // 异步获取帧图片,可以一次获取多帧图片 - (void)centerFrameImageWithVideoURL:(NSURL *)videoURLcompletion:(void (^)(UIImage *image))completion {   // AVAssetImageGenerator   AVAsset *asset = [AVAssetassetWithURL:videoURL];   AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc]initWithAsset:asset];   imageGenerator.appliesPreferredTrackTransform = YES;      // calculate the midpoint time of video   Float64 duration = CMTimeGetSeconds([assetduration]);   // 取某个帧的时间,参数一表示哪个时间(秒),参数二表示每秒多少帧   // 通常来说,600是一个常用的公共参数,苹果有说明:   // 24 frames per second (fps) for film, 30 fps for NTSC (used for TV in North America and   // Japan), and 25 fps for PAL (used for TV in Europe).   // Using a timescale of 600, you can exactly represent any number of frames in these systems   CMTime midpoint = CMTimeMakeWithSeconds(duration / 2.0, 600);      // 异步获取多帧图片   NSValue *midTime = [NSValuevalueWithCMTime:midpoint];   [imageGeneratorgenerateCGImagesAsynchronouslyForTimes:@[midTime]completionHandler:^(CMTime requestedTime, CGImageRef  _Nullableimage, CMTime actualTime, AVAssetImageGeneratorResult result, NSError * _Nullableerror) {     if (result == AVAssetImageGeneratorSucceeded && image != NULL) {       UIImage *centerFrameImage = [[UIImage alloc]initWithCGImage:image];       dispatch_async(dispatch_get_main_queue(), ^{         if (completion) {           completion(centerFrameImage);         }       });     } else {       dispatch_async(dispatch_get_main_queue(), ^{         if (completion) {           completion(nil);         }       });     }   }]; }   

压缩并导出视频

压缩视频是因为视频分辨率过高所生成的视频的大小太大了,对于移动设备来说,内存是不能太大的,如果不支持分片上传到服务器,或者不支持流上传、文件上传,而只能支持表单上传,那么必须要限制大小,压缩视频。

就像我们在使用某平台的视频的上传的时候,到现在还没有支持流上传,也不支持文件上传,只支持表单上传,导致视频大一点就会闪退。流上传是上传成功了,但是人家后台不识别,这一次让某平台坑坏了。直接用file上传,也传过去了,上传进度100%了,但是人家那边还是作为失败处理,无奈!

言归正传,压缩、导出视频,需要通过AVAssetExportSession来实现,我们需要指定一个preset,并判断是否支持这个preset,只有支持才能使用。

我们这里设置的preset为AVAssetExportPreset640x480,属于压缩得比较厉害的了,这需要根据服务器视频上传的支持程度而选择的。然后通过调用异步压缩并导出视频:

  - (void)compressVideoWithVideoURL:(NSURL *)videoURL                         savedName:(NSString *)savedName                        completion:(void (^)(NSString *savedPath))completion {   // Accessing video by URL   AVURLAsset *videoAsset = [[AVURLAsset alloc]initWithURL:videoURLoptions:nil];      // Find compatible presets by video asset.   NSArray *presets = [AVAssetExportSessionexportPresetsCompatibleWithAsset:videoAsset];      // Begin to compress video   // Now we just compress to low resolution if it supports   // If you need to upload to the server, but server does't support to upload by streaming,   // You can compress the resolution to lower. Or you can support more higher resolution.   if ([presetscontainsObject:AVAssetExportPreset640x480]) {     AVAssetExportSession *session = [[AVAssetExportSession alloc]initWithAsset:videoAsset  presetName:AVAssetExportPreset640x480];          NSString *doc = [NSHomeDirectory()stringByAppendingPathComponent:@"Documents"];     NSString *folder = [docstringByAppendingPathComponent:@"HYBVideos"];     BOOL isDir = NO;     BOOL isExist = [[NSFileManager defaultManager]fileExistsAtPath:folderisDirectory:&isDir];     if (!isExist || (isExist && !isDir)) {       NSError *error = nil;       [[NSFileManager defaultManager]createDirectoryAtPath:folder                                 withIntermediateDirectories:YES                                                  attributes:nil                                                       error:&error];       if (error == nil) {         NSLog(@"目录创建成功");       } else {         NSLog(@"目录创建失败");       }     }          NSString *outPutPath = [folderstringByAppendingPathComponent:savedName];     session.outputURL = [NSURLfileURLWithPath:outPutPath];          // Optimize for network use.     session.shouldOptimizeForNetworkUse = true;          NSArray *supportedTypeArray = session.supportedFileTypes;     if ([supportedTypeArraycontainsObject:AVFileTypeMPEG4]) {       session.outputFileType = AVFileTypeMPEG4;     } else if (supportedTypeArray.count == 0) {       NSLog(@"No supported file types");       return;     } else {       session.outputFileType = [supportedTypeArrayobjectAtIndex:0];     }          // Begin to export video to the output path asynchronously.     [sessionexportAsynchronouslyWithCompletionHandler:^{       if ([sessionstatus] == AVAssetExportSessionStatusCompleted) {         dispatch_async(dispatch_get_main_queue(), ^{           if (completion) {             completion([session.outputURLpath]);           }         });       } else {         dispatch_async(dispatch_get_main_queue(), ^{           if (completion) {             completion(nil);           }         });       }     }];   } }   

解决iOS8上录视频引起的偏移bug

在iOS8上有这么一样bug:弹出录制视频页面,再回来发现整个view都往下移动了,可能网上有很多解决办法,下面只是其中一种:

  [pickerdismissViewControllerAnimated:YEScompletion:^{     // for fixing iOS 8.0 problem that frame changed when open camera to record video.     self.tabBarController.view.frame  = [[UIScreen mainScreen]bounds];     [self.tabBarController.viewlayoutIfNeeded]; }];   

Tip:记得在选择或者取消的代理中都调用!

小结

做每种需求,都可能会遇到坑,不过再多的坑也抵不过一颗对技术执着追求的心,必定荡平一切的坑。以前也没有怎么弄过视频类的需求,而别人超过的路,即使有坑也不会告诉后来的人坑在哪里,往往只是心里记着有个坑就算了。

今天给大家分享出来,是帮助有困难的同志们,这里立了一个牌:坑,请大家不要再跳到坑里了。看完本篇文章,是否有所了解了呢?如果您正在做这方面的需求,代码完全可以直接Copy过去使用哦!

源代码

下载源代码,记得star一下,分享出去:

标哥的技术博客:【 VideoCaptureDemo

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