How to stream a video or a file considering request and response range headers? - asp.net-core-mvc

Question

I am now using FileStreamResult and it works to stream a video, but can't seek it. It always starts again from the beginning.
I was using ByteRangeStreamContent but it seems that it is not available anymore with dnxcore50.
So how to proceed ?
Do i need to manually parse the request range headers and write a custom FileResult that sets the response Content-Range and the rest of the headers and writes the buffer range to the response body or is there something already implemented and i'm missing it ?

Answer 1

Here is a naive implementation of a VideoStreamResult. I am using at the moment (the multipart content part is not tested):
public class VideoStreamResult : FileStreamResult
{
// default buffer size as defined in BufferedStream type
private const int BufferSize = 0x1000;
private string MultipartBoundary = "<qwe123>";
public VideoStreamResult(Stream fileStream, string contentType)
: base(fileStream, contentType)
{
}
public VideoStreamResult(Stream fileStream, MediaTypeHeaderValue contentType)
: base(fileStream, contentType)
{
}
private bool IsMultipartRequest(RangeHeaderValue range)
{
return range != null && range.Ranges != null && range.Ranges.Count > 1;
}
private bool IsRangeRequest(RangeHeaderValue range)
{
return range != null && range.Ranges != null && range.Ranges.Count > 0;
}
protected async Task WriteVideoAsync(HttpResponse response)
{
var bufferingFeature = response.HttpContext.Features.Get<IHttpBufferingFeature>();
bufferingFeature?.DisableResponseBuffering();
var length = FileStream.Length;
var range = response.HttpContext.GetRanges(length);
if (IsMultipartRequest(range))
{
response.ContentType = $"multipart/byteranges; boundary={MultipartBoundary}";
}
else
{
response.ContentType = ContentType.ToString();
}
response.Headers.Add("Accept-Ranges", "bytes");
if (IsRangeRequest(range))
{
response.StatusCode = (int)HttpStatusCode.PartialContent;
if (!IsMultipartRequest(range))
{
response.Headers.Add("Content-Range", $"bytes {range.Ranges.First().From}-{range.Ranges.First().To}/{length}");
}
foreach (var rangeValue in range.Ranges)
{
if (IsMultipartRequest(range)) // I don't know if multipart works
{
await response.WriteAsync($"--{MultipartBoundary}");
await response.WriteAsync(Environment.NewLine);
await response.WriteAsync($"Content-type: {ContentType}");
await response.WriteAsync(Environment.NewLine);
await response.WriteAsync($"Content-Range: bytes {range.Ranges.First().From}-{range.Ranges.First().To}/{length}");
await response.WriteAsync(Environment.NewLine);
}
await WriteDataToResponseBody(rangeValue, response);
if (IsMultipartRequest(range))
{
await response.WriteAsync(Environment.NewLine);
}
}
if (IsMultipartRequest(range))
{
await response.WriteAsync($"--{MultipartBoundary}--");
await response.WriteAsync(Environment.NewLine);
}
}
else
{
await FileStream.CopyToAsync(response.Body);
}
}
private async Task WriteDataToResponseBody(RangeItemHeaderValue rangeValue, HttpResponse response)
{
var startIndex = rangeValue.From ?? 0;
var endIndex = rangeValue.To ?? 0;
byte[] buffer = new byte[BufferSize];
long totalToSend = endIndex - startIndex;
int count = 0;
long bytesRemaining = totalToSend + 1;
response.ContentLength = bytesRemaining;
FileStream.Seek(startIndex, SeekOrigin.Begin);
while (bytesRemaining > 0)
{
try
{
if (bytesRemaining <= buffer.Length)
count = FileStream.Read(buffer, 0, (int)bytesRemaining);
else
count = FileStream.Read(buffer, 0, buffer.Length);
if (count == 0)
return;
await response.Body.WriteAsync(buffer, 0, count);
bytesRemaining -= count;
}
catch (IndexOutOfRangeException)
{
await response.Body.FlushAsync();
return;
}
finally
{
await response.Body.FlushAsync();
}
}
}
public override async Task ExecuteResultAsync(ActionContext context)
{
await WriteVideoAsync(context.HttpContext.Response);
}
}
And parse request headers range:
public static RangeHeaderValue GetRanges(this HttpContext context, long contentSize)
{
RangeHeaderValue rangesResult = null;
string rangeHeader = context.Request.Headers["Range"];
if (!string.IsNullOrEmpty(rangeHeader))
{
// rangeHeader contains the value of the Range HTTP Header and can have values like:
// Range: bytes=0-1 * Get bytes 0 and 1, inclusive
// Range: bytes=0-500 * Get bytes 0 to 500 (the first 501 bytes), inclusive
// Range: bytes=400-1000 * Get bytes 500 to 1000 (501 bytes in total), inclusive
// Range: bytes=-200 * Get the last 200 bytes
// Range: bytes=500- * Get all bytes from byte 500 to the end
//
// Can also have multiple ranges delimited by commas, as in:
// Range: bytes=0-500,600-1000 * Get bytes 0-500 (the first 501 bytes), inclusive plus bytes 600-1000 (401 bytes) inclusive
// Remove "Ranges" and break up the ranges
string[] ranges = rangeHeader.Replace("bytes=", string.Empty).Split(",".ToCharArray());
rangesResult = new RangeHeaderValue();
for (int i = 0; i < ranges.Length; i++)
{
const int START = 0, END = 1;
long endByte, startByte;
long parsedValue;
string[] currentRange = ranges[i].Split("-".ToCharArray());
if (long.TryParse(currentRange[END], out parsedValue))
endByte = parsedValue;
else
endByte = contentSize - 1;
if (long.TryParse(currentRange[START], out parsedValue))
startByte = parsedValue;
else
{
// No beginning specified, get last n bytes of file
// We already parsed end, so subtract from total and
// make end the actual size of the file
startByte = contentSize - endByte;
endByte = contentSize - 1;
}
rangesResult.Ranges.Add(new RangeItemHeaderValue(startByte, endByte));
}
}
return rangesResult;
}

Answer 2

FYI, built-in support for range requests will be present in .NET Core 2.1
https://github.com/aspnet/Mvc/pull/6895