c# - IOS 客户端的流视频问题(在 ASP.NET WEB API 2 上开发的服务器)

Question

我对流式视频有疑问。我在 ASP.NET Web API 2 上开发了服务器并实现了 2 种方法:

第一种方法:

if (Request.Headers.Range != null)
    {
        try
        {
            var httpResponce = Request.CreateResponse();
            httpResponce.Content =
                new PushStreamContent((Action<Stream, HttpContent, TransportContext>) WriteContentToStream);

            return httpResponce;
        }
        catch (Exception ex)
        {
            return new HttpResponseMessage(HttpStatusCode.InternalServerError);
        }
    }
    else
    {
        return new HttpResponseMessage(HttpStatusCode.RequestedRangeNotSatisfiable);
    }

/*method for streaming*/

private async void WriteContentToStream(Stream outputStream, HttpContent content, TransportContext transportContext)
{
    string relativeFilePath = "~/App_Data/Videos/4.mp4";
    try
    {
        var filePath = System.Web.Hosting.HostingEnvironment.MapPath(relativeFilePath);

        int bufferSize = 1000;
        byte[] buffer = new byte[bufferSize];
        using (var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read))
        {
            int totalSize = (int)fileStream.Length;
            while (totalSize > 0)
            {
                int count = totalSize > bufferSize ? bufferSize : totalSize;
                int sizeOfReadedBuffer = fileStream.Read(buffer, 0, count);
                await outputStream.WriteAsync(buffer, 0, sizeOfReadedBuffer);
                totalSize -= sizeOfReadedBuffer;
            }
        }
    }
    catch (HttpException ex)
    {
        if (ex.ErrorCode == -2147023667)  
        {
            return;
        }
    }
    finally
    {
        outputStream.Close();
    }
}

2)第二种方法:

public HttpResponseMessage Test()
{
    if (Request.Headers.Range != null)
    {
        try 
        {
            string relativeFilePath = "~/App_Data/Videos/4.mp4";
            var filePath = System.Web.Hosting.HostingEnvironment.MapPath(relativeFilePath);
            HttpResponseMessage partialResponse = Request.CreateResponse(HttpStatusCode.PartialContent);
            partialResponse.Headers.AcceptRanges.Add("bytes");
            var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
            partialResponse.Content = new ByteRangeStreamContent(stream, Request.Headers.Range, new MediaTypeHeaderValue("video/mp4")); 
            return partialResponse;
        }
        catch (Exception)
        {
            return new HttpResponseMessage(HttpStatusCode.InternalServerError);
        }
    }   
    else
    {
        return new HttpResponseMessage(HttpStatusCode.RequestedRangeNotSatisfiable);    
    }
}

这两种方法在Web客户端和Android客户端都有效，但iOS客户端不显示视频。

我认为，这个问题可能出在视频的编解码器(但我使用的是推荐 Apple 的编解码器)或 http-headers。

Answer 1

我刚刚解决了这个问题，这是因为 Content-Length header 具有(iOS 认为的)无效值。

我的解决方案基于上面的方法 #2...这是我的代码中实际有效的重要部分。

if (!file.Exists) {
    response.StatusCode = HttpStatusCode.NotFound;
    response.ReasonPhrase = "Deleted";
} else {
    var range = Request.Headers.Range?.Ranges?.FirstOrDefault();
    if (range == null) {
        using (var stream = new MemoryStream()) {
            using (var video = file.OpenRead()) await video.CopyToAsync(stream);
            response.Content = new ByteArrayContent(stream.ToArray());
        }
        response.Content.Headers.ContentType = new MediaTypeHeaderValue("video/mp4");
        response.Content.Headers.ContentLength = file.Length;
    } else {
        var stream = new MemoryStream();
        using (var video = file.OpenRead()) await video.CopyToAsync(stream);
        response.Content = new ByteRangeStreamContent(
            stream,
            new RangeHeaderValue(range.From, range.To),
            new MediaTypeHeaderValue("video/mp4")
        );
        //  response.Content.Headers.ContentLength = file.Length;
        // this is what makes iOS work
        response.Content.Headers.ContentLength = (range.To.HasValue ? range.To.Value + 1 : file.Length) - (range.From ?? 0);
    }
    response.StatusCode = HttpStatusCode.OK;
}

在处理范围时，我可能应该设置 HTTP 206(部分内容)状态，但在提出解决方案之前我已经为此工作了将近两天。

我尚未完全查明的唯一问题是，Application_EndRequest 有时不会为其中的某些请求触发。我能够记录端点发送的响应，但它就像 iOS 在某处断开连接并且请求挂起，直到它在内部超时。