[英]Getting video from ALAsset
使用iOS 4中提供的新資產庫框架,我看到我可以使用UIImagePickerControllerReferenceURL獲取給定視頻的URL。 返回的url采用以下格式:
assets-library://asset/asset.M4V?id=1000000004&ext=M4V
我正在嘗試將此視頻上傳到網站,以便快速證明我正在嘗試以下內容
NSData *data = [NSData dataWithContentsOfURL:videourl];
[data writeToFile:tmpfile atomically:NO];
在這種情況下,數據永遠不會初始化。 有沒有人設法通過新資產庫直接訪問網址? 謝謝你的幫助。
我在ALAsset
上使用以下類別:
static const NSUInteger BufferSize = 1024*1024;
@implementation ALAsset (Export)
- (BOOL) exportDataToURL: (NSURL*) fileURL error: (NSError**) error
{
[[NSFileManager defaultManager] createFileAtPath:[fileURL path] contents:nil attributes:nil];
NSFileHandle *handle = [NSFileHandle fileHandleForWritingToURL:fileURL error:error];
if (!handle) {
return NO;
}
ALAssetRepresentation *rep = [self defaultRepresentation];
uint8_t *buffer = calloc(BufferSize, sizeof(*buffer));
NSUInteger offset = 0, bytesRead = 0;
do {
@try {
bytesRead = [rep getBytes:buffer fromOffset:offset length:BufferSize error:error];
[handle writeData:[NSData dataWithBytesNoCopy:buffer length:bytesRead freeWhenDone:NO]];
offset += bytesRead;
} @catch (NSException *exception) {
free(buffer);
return NO;
}
} while (bytesRead > 0);
free(buffer);
return YES;
}
@end
這不是最好的方法。 我正在回答這個問題,以防另一個SO用戶遇到同樣的問題。
基本上我的需要是能夠將視頻文件假脫機到tmp文件,以便我可以使用ASIHTTPFormDataRequest將其上傳到網站。 可能有一種從資產網址流式傳輸到ASIHTTPFormDataRequest上傳的方法,但我無法理解。 相反,我編寫了以下函數將文件刪除到tmp文件以添加到ASIHTTPFormDataRequest。
+(NSString*) videoAssetURLToTempFile:(NSURL*)url
{
NSString * surl = [url absoluteString];
NSString * ext = [surl substringFromIndex:[surl rangeOfString:@"ext="].location + 4];
NSTimeInterval ti = [[NSDate date]timeIntervalSinceReferenceDate];
NSString * filename = [NSString stringWithFormat: @"%f.%@",ti,ext];
NSString * tmpfile = [NSTemporaryDirectory() stringByAppendingPathComponent:filename];
ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset)
{
ALAssetRepresentation * rep = [myasset defaultRepresentation];
NSUInteger size = [rep size];
const int bufferSize = 8192;
NSLog(@"Writing to %@",tmpfile);
FILE* f = fopen([tmpfile cStringUsingEncoding:1], "wb+");
if (f == NULL) {
NSLog(@"Can not create tmp file.");
return;
}
Byte * buffer = (Byte*)malloc(bufferSize);
int read = 0, offset = 0, written = 0;
NSError* err;
if (size != 0) {
do {
read = [rep getBytes:buffer
fromOffset:offset
length:bufferSize
error:&err];
written = fwrite(buffer, sizeof(char), read, f);
offset += read;
} while (read != 0);
}
fclose(f);
};
ALAssetsLibraryAccessFailureBlock failureblock = ^(NSError *myerror)
{
NSLog(@"Can not get asset - %@",[myerror localizedDescription]);
};
if(url)
{
ALAssetsLibrary* assetslibrary = [[[ALAssetsLibrary alloc] init] autorelease];
[assetslibrary assetForURL:url
resultBlock:resultblock
failureBlock:failureblock];
}
return tmpfile;
}
你去......
AVAssetExportSession* m_session=nil;
-(void)export:(ALAsset*)asset withHandler:(void (^)(NSURL* url, NSError* error))handler
{
ALAssetRepresentation* representation=asset.defaultRepresentation;
m_session=[AVAssetExportSession exportSessionWithAsset:[AVURLAsset URLAssetWithURL:representation.url options:nil] presetName:AVAssetExportPresetPassthrough];
m_session.outputFileType=AVFileTypeQuickTimeMovie;
m_session.outputURL=[NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"%f.mov",[NSDate timeIntervalSinceReferenceDate]]]];
[m_session exportAsynchronouslyWithCompletionHandler:^
{
if (m_session.status!=AVAssetExportSessionStatusCompleted)
{
NSError* error=m_session.error;
m_session=nil;
handler(nil,error);
return;
}
NSURL* url=m_session.outputURL;
m_session=nil;
handler(url,nil);
}];
}
如果要重新編碼影片,可以使用不同的預設鍵(例如AVAssetExportPresetMediumQuality
)
這是一個干凈利落的快速解決方案,可以將視頻作為NSData。 它使用Photos框架,因為從iOS9開始不推薦使用ALAssetLibrary:
重要
從iOS 9.0開始,不推薦使用Assets Library框架。 相反,請使用Photos框架,在iOS 8.0及更高版本中,它可以為用戶的照片庫提供更多功能和更好的性能。 有關更多信息,請參閱照片框架參考。
import Photos
func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
self.dismissViewControllerAnimated(true, completion: nil)
if let referenceURL = info[UIImagePickerControllerReferenceURL] as? NSURL {
let fetchResult = PHAsset.fetchAssetsWithALAssetURLs([referenceURL], options: nil)
if let phAsset = fetchResult.firstObject as? PHAsset {
PHImageManager.defaultManager().requestAVAssetForVideo(phAsset, options: PHVideoRequestOptions(), resultHandler: { (asset, audioMix, info) -> Void in
if let asset = asset as? AVURLAsset {
let videoData = NSData(contentsOfURL: asset.URL)
// optionally, write the video to the temp directory
let videoPath = NSTemporaryDirectory() + "tmpMovie.MOV"
let videoURL = NSURL(fileURLWithPath: videoPath)
let writeResult = videoData?.writeToURL(videoURL, atomically: true)
if let writeResult = writeResult where writeResult {
print("success")
}
else {
print("failure")
}
}
})
}
}
}
這是Alonzo答案的Objective C解決方案,使用照片框架
-(NSURL*)createVideoCopyFromReferenceUrl:(NSURL*)inputUrlFromVideoPicker{
NSURL __block *videoURL;
PHFetchResult *phAssetFetchResult = [PHAsset fetchAssetsWithALAssetURLs:@[inputUrlFromVideoPicker ] options:nil];
PHAsset *phAsset = [phAssetFetchResult firstObject];
dispatch_group_t group = dispatch_group_create();
dispatch_group_enter(group);
[[PHImageManager defaultManager] requestAVAssetForVideo:phAsset options:nil resultHandler:^(AVAsset *asset, AVAudioMix *audioMix, NSDictionary *info) {
if ([asset isKindOfClass:[AVURLAsset class]]) {
NSURL *url = [(AVURLAsset *)asset URL];
NSLog(@"Final URL %@",url);
NSData *videoData = [NSData dataWithContentsOfURL:url];
// optionally, write the video to the temp directory
NSString *videoPath = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"%f.mp4",[NSDate timeIntervalSinceReferenceDate]]];
videoURL = [NSURL fileURLWithPath:videoPath];
BOOL writeResult = [videoData writeToURL:videoURL atomically:true];
if(writeResult) {
NSLog(@"video success");
}
else {
NSLog(@"video failure");
}
dispatch_group_leave(group);
// use URL to get file content
}
}];
dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
return videoURL;
}
這來自Zoul的回答謝謝
Similar Code in Xamarin C#
Xamarin C#等效
IntPtr buffer = CFAllocator.Malloc.Allocate(representation.Size);
NSError error;
nuint buffered = representation.GetBytes(buffer, Convert.ToInt64(0.0),Convert.ToUInt32(representation.Size),out error);
NSData sourceData = NSData.FromBytesNoCopy(buffer,buffered,true);
NSFileManager fileManager = NSFileManager.DefaultManager;
NSFileAttributes attr = NSFileAttributes.FromDictionary(NSDictionary.FromFile(outputPath));
fileManager.CreateFile(outputPath, sourceData,attr);
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