Stream disconnect when scene changes from total darkness abruptly

[dustinkerstein]

First of all, thanks for this awesome demo. It's working perfectly 99% of the time.

A minor issue, though definitely a snag for my usage, is when the scene changes from total darkness (ie. taking lens cap off) the stream will disconnect with the error:

Error received while reading the MJPEG.

Any ideas on why this could be happening? Are you able to replicate? Thanks!

[DanielArnett]

Weird. Before I try to replicate, what if you add in a try, catch around the part that's failing? Maybe it's just one frame that's messed up, and if we just skip it and wait for the frame after it'll be fine?

…

On Sun, Nov 15, 2020, 8:25 AM dustinkerstein ***@***.***> wrote: First of all, thanks for this awesome demo. It's working perfectly 99% of the time. A minor issue, though definitely a snag for my usage, is when the scene changes from total darkness (ie. taking lens cap off) the stream will disconnect with the error: Error received while reading the MJPEG. Any ideas on why this could be happening? Are you able to replicate? Thanks! — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#4>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAXDT7T2GCDS4V2UEQQZK73SP7JF3ANCNFSM4TWGGQAA> .

[dustinkerstein]

Yeah, that sound good. It's happening somewhere in OnGetResponse which already has a try, catch. I can definitely add some more, but do you have any inclination as to which part inside that chunk of code I should debug first? Thanks for the quick reply!

[dustinkerstein]

Here's that chunk of code for reference:

private void OnGetResponse(IAsyncResult asyncResult)
    {
        responseReceived = true;
        //Debug.Log("OnGetResponse");
        byte[] imageBuffer = new byte[1024 * 1024];

        //Debug.Log("Starting request");
        // get the response
        HttpWebRequest req = (HttpWebRequest)asyncResult.AsyncState;

        try
        {
            //Debug.Log("OnGetResponse try entered.");
            HttpWebResponse resp = (HttpWebResponse)req.EndGetResponse(asyncResult);
            //Debug.Log("response received");
            // find our magic boundary value
            string contentType = resp.Headers["Content-Type"];
            if (!string.IsNullOrEmpty(contentType) && !contentType.Contains("="))
            {
                Debug.Log("MJPEG Exception thrown");
                throw new Exception("Invalid content-type header.  The camera is likely not returning a proper MJPEG stream.");
            }

            string boundary = resp.Headers["Content-Type"].Split('=')[1].Replace("\"", "");
            byte[] boundaryBytes = Encoding.UTF8.GetBytes(boundary.StartsWith("--") ? boundary : "--" + boundary);

            Stream s = resp.GetResponseStream();
            BinaryReader br = new BinaryReader(s);

            _streamActive = true;
            byte[] buff = br.ReadBytes(_chunkSize);

            while (_streamActive)
            {
                // find the JPEG header
                int imageStart = FindBytes(buff, JpegHeader);// buff.Find(JpegHeader);

                if (imageStart != -1)
                {
                    // copy the start of the JPEG image to the imageBuffer
                    int size = buff.Length - imageStart;
                    Array.Copy(buff, imageStart, imageBuffer, 0, size);

                    while (true)
                    {
                        buff = br.ReadBytes(_chunkSize);

                        // Find the end of the jpeg
                        int imageEnd = FindBytes(buff, boundaryBytes);
                        if (imageEnd != -1)
                        {
                            // copy the remainder of the JPEG to the imageBuffer
                            Array.Copy(buff, 0, imageBuffer, size, imageEnd);
                            size += imageEnd;

                            // Copy the latest frame into `CurrentFrame`
                            byte[] frame = new byte[size];
                            Array.Copy(imageBuffer, 0, frame, 0, size);
                            CurrentFrame = frame;

                            // tell whoever's listening that we have a frame to draw
                            if (FrameReady != null)
                                FrameReady(this, new FrameReadyEventArgs());
                            // copy the leftover data to the start
                            Array.Copy(buff, imageEnd, buff, 0, buff.Length - imageEnd);

                            // fill the remainder of the buffer with new data and start over
                            byte[] temp = br.ReadBytes(imageEnd);

                            Array.Copy(temp, 0, buff, buff.Length - imageEnd, temp.Length);
                            break;
                        }

                        // copy all of the data to the imageBuffer
                        Array.Copy(buff, 0, imageBuffer, size, buff.Length);
                        size += buff.Length;

                        if (!_streamActive)
                        {
                            //Debug.Log("CLOSING");
                            resp.Close();
                            break;
                        }
                    }
                }
            }
            resp.Close();
        }
        catch (Exception ex)
        {
            if (Error != null)
                _context.Post(delegate { Error(this, new ErrorEventArgs() { Message = ex.Message }); }, null);

            return;
        }
    }
}

[DanielArnett]

IDK I wrote it years ago. You know more about it than I do at this point. Keep throwing debug and print statements until you find the error. Also it might have try catches where the bad image is coming in, but still trying to use the empty image. If you can tell me where the actual crash is happening I might be able to help more.

…

On Sun, Nov 15, 2020, 8:52 AM dustinkerstein ***@***.***> wrote: Here's that chunk of code for reference: private void OnGetResponse(IAsyncResult asyncResult) { responseReceived = true; //Debug.Log("OnGetResponse"); byte[] imageBuffer = new byte[1024 * 1024]; //Debug.Log("Starting request"); // get the response HttpWebRequest req = (HttpWebRequest)asyncResult.AsyncState; try { //Debug.Log("OnGetResponse try entered."); HttpWebResponse resp = (HttpWebResponse)req.EndGetResponse(asyncResult); //Debug.Log("response received"); // find our magic boundary value string contentType = resp.Headers["Content-Type"]; if (!string.IsNullOrEmpty(contentType) && !contentType.Contains("=")) { Debug.Log("MJPEG Exception thrown"); throw new Exception("Invalid content-type header. The camera is likely not returning a proper MJPEG stream."); } string boundary = resp.Headers["Content-Type"].Split('=')[1].Replace("\"", ""); byte[] boundaryBytes = Encoding.UTF8.GetBytes(boundary.StartsWith("--") ? boundary : "--" + boundary); Stream s = resp.GetResponseStream(); BinaryReader br = new BinaryReader(s); _streamActive = true; byte[] buff = br.ReadBytes(_chunkSize); while (_streamActive) { // find the JPEG header int imageStart = FindBytes(buff, JpegHeader);// buff.Find(JpegHeader); if (imageStart != -1) { // copy the start of the JPEG image to the imageBuffer int size = buff.Length - imageStart; Array.Copy(buff, imageStart, imageBuffer, 0, size); while (true) { buff = br.ReadBytes(_chunkSize); // Find the end of the jpeg int imageEnd = FindBytes(buff, boundaryBytes); if (imageEnd != -1) { // copy the remainder of the JPEG to the imageBuffer Array.Copy(buff, 0, imageBuffer, size, imageEnd); size += imageEnd; // Copy the latest frame into `CurrentFrame` byte[] frame = new byte[size]; Array.Copy(imageBuffer, 0, frame, 0, size); CurrentFrame = frame; // tell whoever's listening that we have a frame to draw if (FrameReady != null) FrameReady(this, new FrameReadyEventArgs()); // copy the leftover data to the start Array.Copy(buff, imageEnd, buff, 0, buff.Length - imageEnd); // fill the remainder of the buffer with new data and start over byte[] temp = br.ReadBytes(imageEnd); Array.Copy(temp, 0, buff, buff.Length - imageEnd, temp.Length); break; } // copy all of the data to the imageBuffer Array.Copy(buff, 0, imageBuffer, size, buff.Length); size += buff.Length; if (!_streamActive) { //Debug.Log("CLOSING"); resp.Close(); break; } } } } resp.Close(); } catch (Exception ex) { if (Error != null) _context.Post(delegate { Error(this, new ErrorEventArgs() { Message = ex.Message }); }, null); return; } } } — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAXDT7R7HBD22WKEPBUK2LDSP7MJJANCNFSM4TWGGQAA> .

[dustinkerstein]

It looks like it's happening here:

Array.Copy(buff, 0, imageBuffer, size, buff.Length);

But none of the variables are zero/null as when I Debug.Log("size: " + size + " imageBuffer length: " + imageBuffer.Length + " buff.Length: " + buff.Length) before that line I get:

size: 1048515 imageBuffer length: 1048576 buff.Length: 4096

I'll try a little more debug now.

[dustinkerstein]

Ah, the buffer size was too small based on the 4096 offset. I increased the buffer to byte[] imageBuffer = new byte[2048 * 2048] and it seems to have resolved this issue. Let me know if you see a better way to address that. Thanks!