我们正在xamarin本机上构建一个移动聊天应用程序。我们在视频方面遇到问题 由于某些编码问题，从IOS应用程序发送的视频无法在android设备的默认媒体播放器上播放。
为解决此问题，我们正在服务器上转换视频，而该服务器对此进行了大量处理。
建立此过程的方法是什么？也许在发送视频之前先在设备上对视频进行编码？
谢谢。
我们使用从建议中转换而来的内容，但未进行转换，并且选择器卡在了视频快照上：
Picker = new UIImagePickerController()
{
SourceType = type,
MediaTypes = UIImagePickerController.AvailableMediaTypes(type),
VideoExportPreset = AVAssetExportSessionPreset.Passthrough.GetConstant().ToString(),
VideoQuality = UIImagePickerControllerQualityType.Medium,
//AllowsImageEditing = false,
VideoMaximumDuration = 120f
};
var srcUrl = e.Info[UIImagePickerController.MediaURL] as NSUrl;
AVUrlAsset avAsset = new AVUrlAsset(srcUrl, new NSDictionary());
string[] compatiblePresets = AVAssetExportSession.ExportPresetsCompatibleWithAsset(avAsset);
if (compatiblePresets.Contains("AVAssetExportPresetLowQuality"))
{
AVAssetExportSession exportSession = new AVAssetExportSession(avAsset, AVAssetExportSessionPreset.Passthrough);
//var destFile = fileService.MoveFileToMyDocument(srcUrl.Path, ChatMessageType.Video);
string destFile = System.IO.Path.Combine(System.IO.Path.GetTempPath(), Guid.NewGuid().ToString() + ".mp4");
exportSession.OutputUrl = new NSUrl(destFile);
exportSession.OutputFileType = AVFileType.Mpeg4;
exportSession.ShouldOptimizeForNetworkUse = true;
exportSession.ExportAsynchronously(() =>
{
switch (exportSession.Status)
{
case AVAssetExportSessionStatus.Failed:
//If this fails, it might be because the temorary
//files weren't cleaned and this isn't overwriting
//the temporary filename
Console.WriteLine(@"Export failed: " + exportSession.Error.LocalizedDescription);
//Perform any failed logic
Picker.DismissViewControllerAsync(true);
break;
case AVAssetExportSessionStatus.Cancelled:
Console.WriteLine(@"Export canceled");
//Perform any cancel logic
Picker.DismissViewControllerAsync(true);
break;
default:
//This should have been a success
//File should be saved at filePath
//Upload file from here
var url = fileService.GetFullPath(exportSession.OutputUrl.ToString());
SendMedia(url, ChatMessageType.Video);
break;
}
});
}
这在日志中显示：
System.NotSupportedException: Specified method is not supported.
at Mono.Debugger.Soft.VirtualMachine.EncodeValue (Mono.Debugger.Soft.Value v, System.Collections.Generic.List`1[T] duplicates) [0x000df] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs:686
at Mono.Debugger.Soft.VirtualMachine.EncodeValues (System.Collections.Generic.IList`1[T] values, System.Collections.Generic.List`1[T] duplicates) [0x00010] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs:693
at Mono.Debugger.Soft.ObjectMirror.BeginInvokeMethod (Mono.Debugger.Soft.VirtualMachine vm, Mono.Debugger.Soft.ThreadMirror thread, Mono.Debugger.Soft.MethodMirror method, Mono.Debugger.Soft.Value this_obj, System.Collections.Generic.IList`1[T] arguments, Mono.Debugger.Soft.InvokeOptions options, System.AsyncCallback callback, System.Object state) [0x00094] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugger.Soft/Mono.Debugger.Soft/ObjectMirror.cs:311
at Mono.Debugger.Soft.ObjectMirror.InvokeMethod (Mono.Debugger.Soft.VirtualMachine vm, Mono.Debugger.Soft.ThreadMirror thread, Mono.Debugger.Soft.MethodMirror method, Mono.Debugger.Soft.Value this_obj, System.Collections.Generic.IList`1[T] arguments, Mono.Debugger.Soft.InvokeOptions options) [0x00000] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugger.Soft/Mono.Debugger.Soft/ObjectMirror.cs:387
at Mono.Debugger.Soft.TypeMirror.NewInstance (Mono.Debugger.Soft.ThreadMirror thread, Mono.Debugger.Soft.MethodMirror method, System.Collections.Generic.IList`1[T] arguments, Mono.Debugger.Soft.InvokeOptions options) [0x00026] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugger.Soft/Mono.Debugger.Soft/TypeMirror.cs:837
at Mono.Debugger.Soft.TypeMirror.NewInstance (Mono.Debugger.Soft.ThreadMirror thread, Mono.Debugger.Soft.MethodMirror method, System.Collections.Generic.IList`1[T] arguments) [0x00000] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugger.Soft/Mono.Debugger.Soft/TypeMirror.cs:827
at Mono.Debugging.Soft.SoftDebuggerAdaptor.CreateValue (Mono.Debugging.Evaluation.EvaluationContext ctx, System.Object type, System.Object[] argValues) [0x0019e] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugging.Soft/SoftDebuggerAdaptor.cs:524
at Mono.Debugging.Evaluation.NRefactoryExpressionEvaluatorVisitor.VisitObjectCreateExpression (ICSharpCode.NRefactory.CSharp.ObjectCreateExpression objectCreateExpression) [0x0005e] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugging/Mono.Debugging.Evaluation/NRefactoryExpressionEvaluatorVisitor.cs:1081
at ICSharpCode.NRefactory.CSharp.ObjectCreateExpression.AcceptVisitor[T] (ICSharpCode.NRefactory.CSharp.IAstVisitor`1[S] visitor) [0x00000] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/nrefactory/ICSharpCode.NRefactory.CSharp/Ast/Expressions/ObjectCreateExpression.cs:90
at Mono.Debugging.Evaluation.NRefactoryExpressionEvaluator.Evaluate (Mono.Debugging.Evaluation.EvaluationContext ctx, System.String expression, System.Object expectedType) [0x00157] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugging/Mono.Debugging.Evaluation/NRefactoryExpressionEvaluator.cs:82
at Mono.Debugging.Evaluation.ExpressionEvaluator.Evaluate (Mono.Debugging.Evaluation.EvaluationContext ctx, System.String exp) [0x00000] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugging/Mono.Debugging.Evaluation/ExpressionEvaluator.cs:43
at Mono.Debugging.Evaluation.ObjectValueAdaptor.GetExpressionValue (Mono.Debugging.Evaluation.EvaluationContext ctx, System.String exp) [0x00000] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/external/debugger-libs/Mono.Debugging/Mono.Debugging.Evaluation/ObjectValueAdaptor.cs:1416 Thread started: #13
Thread finished: <Thread Pool> #6
2019-07-10 10:14:25.501 MyApp[319:18031] Export failed: The operation could not be completed
答案 0 :(得分：0)
据我所知，由于iPhone拥有的视频类型为MOV，因此会出现此问题，但是当您在Android上播放该视频类型时，由于默认情况下它不支持Android，因此您需要像VLC这样的视频播放器为它工作。如果您问我，解决此问题的最佳方法是视频转换，可以在Xamarin iOS中使用AVAssetExportSession。
您所做的是这样的：
var asset = AVAsset.FromUrl( NSUrl.FromFilename( sourceFilePath ) )
AVAssetExportSession export = new AVAssetExportSession (asset, AVAssetExportSession.PresetLowQuality );
export.OutputUrl = new NSUrl ( downloadFilePath );
export.OutputFileType = AVFileType.Mpeg4;
export.ShouldOptimizeForNetworkUse = true;
export.ExportAsynchronously( ( ) =>
{
System.Diagnostics.Debug.WriteLine( export.Error.LocalizedDescription );
});
您可以检查此Xamarin Forums discussion以获得更多详细信息。
您还可以检查此StackOverflow问题，该问题处理类似MOV to Mp4 video conversion iPhone programmatically