Playing video stream from mp4 file with moov atom at end using libvlcsharp

Question

I want to play video replay from low-end surveillance camera. Replays are saved on the camera in .mp4 format, with moov atom at the end. It's possible to retrieve file via http request using digset authentication. Approximate size of each video file is 20 MB, but download speed is only 3 Mbps, so downloading whole file takes about 60 s. This is to long, so I want to start displaying video before whole file will be downloaded.

Web browsers handles this kind of problem by reading end of file at the begining. I want to achieve same goal using c# and libvlcsharp, so created HttpMediaInput class.

public class HttpMediaInput : MediaInput
    {
        private static readonly NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger();

        private HttpClientHandler _handler;
        private HttpClient _httpClient;
        private string _url;
        Stream _stream = null;

        public HttpMediaInput(string url, string username, string password)
        {
            _url = url;
            _handler = new HttpClientHandler() { Credentials = new NetworkCredential(username, password) };
            _httpClient = new HttpClient(_handler);
        }

        public override bool Open(out ulong size)
        {
            size = ulong.MaxValue;
            try
            {
                _stream = _httpClient.GetStreamAsync(_url).Result;
                base.CanSeek = _stream.CanSeek;
                return true;
            }
            catch (Exception ex)
            {
                logger.Error(ex, $"Exception occurred during sending stream request to url: {_url}");
                return false;
            }
        }

        public unsafe override int Read(IntPtr buf, uint len)
        {
            try
            {
                byte[] buffer = new byte[len];
                int bytesReaded = _stream.Read(buffer, 0, buffer.Length);
                logger.Trace($"Bytes readed: {bytesReaded}");
                Span<byte> byteSpan = new Span<byte>(buf.ToPointer(), buffer.Length);
                buffer.CopyTo(byteSpan);
                
                return bytesReaded;
            }
            catch (Exception ex)
            {
                logger.Error(ex, "Stream read exception");
                return -1;
            }
        }

       ...
        
    }

It works great for mp4 files that have all necessary metadata stored on the beginning, but no video is displayed in case of my camera.

Assuming that I will be able to download moov atom from mp4 using http range requests, how to provide this data to libvlc? Is it even possible?

I'm developing application using C#, WPF, dotnet framework.

Answer 1

VLC cannot play files from camera because http digest auth with md5 is considered to be deprecated (related issue in VLC repo).

However, I was able to resolve this problem following cube45 suggestions, I implemented range requests.

    public override bool Open(out ulong size)
        {
            size = ulong.MaxValue;
            try
            {
                HttpRequestMessage requestMessage = new HttpRequestMessage { RequestUri = new Uri(_url) };
                requestMessage.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue();
                requestMessage.Method = HttpMethod.Head;
                var response = _httpClient.SendAsync(requestMessage).Result;
                size = (ulong)response.Content.Headers.ContentLength;
                _fileSize = size;
                logger.Trace($"Received content lenght | {size}");
                base.CanSeek = true;
                return true;
            }
            catch (Exception ex)
            {
                logger.Error(ex, $"Exception occurred during sending head request to url: {_url}");
                return false;
            }
        }

        public unsafe override int Read(IntPtr buf, uint len)
        {
            try
            {
                HttpRequestMessage requestMessage = new HttpRequestMessage { RequestUri = new Uri(_url) };
                long startReadPosition = (long)_currentPosition;
                long stopReadPosition = (long)_currentPosition + ((long)_numberOfBytesToReadInOneRequest - 1);
                if ((ulong)stopReadPosition > _fileSize)
                {
                    stopReadPosition = (long)_fileSize;
                }
                requestMessage.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue(startReadPosition, stopReadPosition);
                requestMessage.Method = HttpMethod.Get;
                HttpResponseMessage response = _httpClient.SendAsync(requestMessage).Result;
                byte[] readedBytes = response.Content.ReadAsByteArrayAsync().Result;
                int readedBytesCount = readedBytes.Length;
                _currentPosition += (ulong)readedBytesCount;
                logger.Trace($"Bytes readed | {readedBytesCount} | startReadPosition {startReadPosition} | stopReadPosition | {stopReadPosition}");
                Span<byte> byteSpan = new Span<byte>(buf.ToPointer(), (int)len);
                readedBytes.CopyTo(byteSpan);

                return readedBytesCount;
            }
            catch (Exception ex)
            {
                logger.Error(ex, "Media reading general exception");
                return -1;
            }
        }

        public override bool Seek(ulong offset)
        {
            try
            {
                logger.Trace($"Seeking media with offset | {offset}");
                _currentPosition = offset;
                return true;
            }
            catch (Exception ex)
            {
                logger.Error(ex, "MediaInput seekeing general error");
                return false;
            }
        }

This solution seams to work, but there are two unresolved problems:

1. There is about 8s lag between libvlcsharp starts reading stream and video goes live (waiting time in web browser is about 2s).
2. Some part of video file at the end is not displayed, because the buffer is too short to hold whole file inside. Related thread