好的,我明白了。基本上,解决方案有两个部分:
- 手动进行HTTP请求(使用任何必需的凭据或标头)
- 将响应流包装在自定义的
IRandomAccessStream
中,该流通过向服务器发出另一个请求来实现Seek
,并使用Range
标头指定我需要的流的哪个部分。
这是RandomAccessStream
实现:
delegate Task<Stream> AsyncRangeDownloader(ulong start, ulong? end);
class StreamingRandomAccessStream : IRandomAccessStream
{
private readonly AsyncRangeDownloader _downloader;
private readonly ulong _size;
public StreamingRandomAccessStream(Stream startStream, AsyncRangeDownloader downloader, ulong size)
{
if (startStream != null)
_stream = startStream.AsInputStream();
_downloader = downloader;
_size = size;
}
private IInputStream _stream;
private ulong _requestedPosition;
public void Dispose()
{
if (_stream != null)
_stream.Dispose();
}
public IAsyncOperationWithProgress<IBuffer, uint> ReadAsync(IBuffer buffer, uint count, InputStreamOptions options)
{
return AsyncInfo.Run<IBuffer, uint>(async (cancellationToken, progress) =>
{
progress.Report(0);
if (_stream == null)
{
var netStream = await _downloader(_requestedPosition, null);
_stream = netStream.AsInputStream();
}
var result = await _stream.ReadAsync(buffer, count, options).AsTask(cancellationToken, progress);
return result;
});
}
public void Seek(ulong position)
{
if (_stream != null)
_stream.Dispose();
_requestedPosition = position;
_stream = null;
}
public bool CanRead { get { return true; } }
public bool CanWrite { get { return false; } }
public ulong Size { get { return _size; } set { throw new NotSupportedException(); } }
public IAsyncOperationWithProgress<uint, uint> WriteAsync(IBuffer buffer) { throw new NotSupportedException(); }
public IAsyncOperation<bool> FlushAsync() { throw new NotSupportedException(); }
public IInputStream GetInputStreamAt(ulong position) { throw new NotSupportedException(); }
public IOutputStream GetOutputStreamAt(ulong position) { throw new NotSupportedException(); }
public IRandomAccessStream CloneStream() { throw new NotSupportedException(); }
public ulong Position { get { throw new NotSupportedException(); } }
}
以下是使用方法:
private HttpClient _client;
private void InitClient()
{
_client = new HttpClient();
}
private async Task StartVideoStreamingAsync(Uri uri)
{
var request = new HttpRequestMessage(HttpMethod.Get, uri);
var response = await _client.SendAsync(request);
ulong length = (ulong)response.Content.Headers.ContentLength;
string mimeType = response.Content.Headers.ContentType.MediaType;
Stream responseStream = await response.Content.ReadAsStreamAsync();
AsyncRangeDownloader downloader = async (start, end) =>
{
var request2 = new HttpRequestMessage();
request2.Headers.Range = new RangeHeaderValue((long?)start, (long?)end);
var response2 = await _client.SendAsync(request2);
return await response2.Content.ReadAsStreamAsync();
};
var videoStream = new StreamingRandomAccessStream(responseStream, downloader, length);
_mediaElement.SetSource(videoStream, mimeType);
}
用户可以在视频中任意位置进行搜索,流媒体将发出另一个请求以获取指定位置的流。这仍然比我想象的要复杂,但它能够工作...请注意,服务器必须支持请求中的“Range”头,并且必须在初始响应中发出“Content-Length”头。
MediaElement
的源设置为该流。 - Nate DiamondRandomAccessStream
。 - Nate Diamond