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• Converting C# void* to byte[]

  - by Yurik

  In C#, I need to write T[] to a stream, ideally without any additional buffers. I have a dynamic code that converts T[] (where T is a no-objects struct) to a void* and fixes it in memory, and that works great. When the stream was a file, I could use native Windows API to pass the void * directly, but now I need to write to a generic Stream object that takes byte[]. Can anyone suggest a hack way to create a dummy array object which does not actually have any heap allocations, but rather points to an already existing (and fixed) heap location. This is the pseudo-code that I need: void Write(Stream stream, T[] buffer) { fixed( void* ptr = &buffer ) // done with dynamic code generation { int typeSize = sizeof(T); // done as well byte[] dummy = (byte[]) ptr; // <-- how do I create this fake array? stream.Write( dummy, 0, buffer.Length*typeSize ); } }

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• Line by line image swing

  - by user1046017

  I want to show an image as it is downloading, I have the URL, and I am trying to get the image parts like this: InputStream openStream = url.openStream(); DataInputStream dis = new DataInputStream(new BufferedInputStream(openStream)); ByteArrayOutputStream os = new ByteArrayOutputStream(); while ((s = dis.read(b)) != -1) { os.write(b , 0, s); support.firePropertyChange("stream", null, os); } This way, any listener get the stream and creates an image, this way: if("stream".equals(evt.getPropertyName())){ try { ByteArrayOutputStream stream = (ByteArrayOutputStream) evt.getNewValue(); byte[] byteArray = stream.toByteArray(); stream.flush(); Image createImage = Toolkit.getDefaultToolkit().createImage(byteArray); this.getContentPane().add(new JLabel(new ImageIcon(createImage))); } catch (IOException ex) { Logger.getLogger(ImageTest.class.getName()).log(Level.SEVERE, null, ex); } } However, I am getting a "Premature end of JPEG file sun.awt.image.ImageFormatException: JPEG datastream contains no image" error, the image is a JPG image format, is there any library or method known to make something similar?

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• Rails: Creating subfolders in model?

  - by keruilin

  I'm going to have a ton of subclasses, so want to organize them under a subfolder called stream. I added the following line to the environment.rb so that all classes in the subfolder would be loaded: Rails::Initializer.run do |config| ... config.load_paths += Dir["#{RAILS_ROOT}/app/models/*"].find_all { |f| File.stat(f).directory? } ... end I thought this would solve the issue in which by convention the model class is namespaced into an according module. However, when I try to call one of the classes called stream in the stream folder, I get the following error: NoMethodError: undefined method `new' for Stream:Module from (irb):28 from /usr/local/bin/irb:12:in `<main>' Here's the model for the parent and one child: class Stream end class EventStream < Stream end Any idea what the issue is?

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• Equivalent of %02d with std::stringstream?

  - by Andreas Brinck

  I wan't to output an integer to a std::stringstream with the equivalent format of printf's %02d. Is there an easier way to achieve this than: std::stringstream stream; stream.setfill('0'); stream.setw(2); stream << value; Is it possible to stream some sort of format flags to the stringstream, something like (pseudocode): stream << flags("%02d") << value;

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• NFS caching on Ubuntu

  - by stream

  We run a bunch of ubuntu servers (mostly 8.04 LTS) which all mount an nfs share at /nfs. We use the nfs primarily for two purposes: symlinking config files (such as apache vhosts) reading & writing uploaded files This all works great except it makes us fully dependent on the central NFS server (which is a DRBD cluster with heartbeat failover from primary to secondary, but we've still seen issues). What we'd like is if we could mount the NFS through some local caching layer which would make any file which had previously been read remain available even if /nfs isn't. Writes could be disabled for this period. Searching around it looks like cachefilesd may be an option. Unfortunately, it's only packaged for ubuntu 9.10 & 10.04 it looks like. I was also looking for a FUSE-based solution which might fit the bill, but hadn't found anything yet. Any suggestions would be greatly appreciated!

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• How to upload a CSV file and and read it's data in the client side itself and send the data as a stream through a ajax post?

  - by sunshine

  I need to upload a CSV file and get its contents form the client side itself. Then post it to the server where I can retriev the stream and do the string manipulations in the serer action methods. Is there any jquery plugin for this task to upload a csv file and send data as a stream using ajax or jason? I am really new to this area.I am working in VS2010 AND mvc3. Can some one give me a clear solution for this mater?? Any examples?? I did search a lot but did not find any suitable solution yet. Can anyone please help me with this matter. Thanks so much.

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• Could the HTML 5 Video tag pick up an IP Multicast Stream?

  - by DrewBarbs

  I've been researching methods of getting an IP Multicast over UDP to the browser, and have found little that suggests I would be able to do it without using a plug-in like Java, Flash, or Silverlight in order to open a UDP port and (somehow) render the video. Checking out the HTML 5 <video> spec, there is (obviously) little in the way of specific implementation details, so as far as I can tell, there is nothing stopping a browser from parsing a address of the form "udp://224.1.1.1:8000" and joining a multicast group on that IP/port. Is this a correct understanding? Or must the resource pointed to by the <source> be a file?

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• ASMX Web Services with SOAP Extension

  - by digitall

  I am in the process of setting up a web service for an external client to connect to my client's application and update some information. I went the ASMX route (the rest of the application runs on WCF) because I knew the external client could be very difficult to deal with and I was trying to keep everything as simple as possible. They also aren't a .Net shop which makes things worse. After getting the service setup for them I provided the ASMX URL for them to see how to format the SOAP headers/message content. They have since come back and told me their tool is unable to send them in the format required by .Net and I can either come up with a different way to accept messages or we have to go with FTP. Based on this I have been researching how to intercept their message, reformat it the way my service requires it (which means adding two lines), and then let it process. This path led me to SOAP Extensions which I have been trying to work with but can't seem to figure out. When I have my sample application call the web service from the generated code Add Web Reference provides everything works great until I add in my extension. All it currently does is override ChainStream setting an internal stream equal to the one being passed in and returning a new stream, like this: private Stream newStream = null; private Stream oldStream = null; public override Stream ChainStream(Stream stream) { this.oldStream = stream; this.newStream = new MemoryStream(); return newStream; } I also override ProcessMessage and in it take the contents of oldStream and set newStream equal to that and then write to a different stream with an XmlWriter. I take that new stream and using a StreamReader read it into a string, with the end goal being manipulating it here and setting newStream (which is being used by ChainStream) equal to the contents of this. Here is that piece: public override void ProcessMessage(SoapMessage message) { switch (message.Stage) { case SoapMessageStage.BeforeDeserialize: this.Process(); break; default: break; } } private void Process() { this.newStream.Position = 0L; XmlTextReader reader = new XmlTextReader(this.oldStream); MemoryStream outStream = new MemoryStream(); using (XmlWriter writer = XmlWriter.Create(outStream)) { do { writer.WriteNode(reader, true); } while (reader.Read()); writer.Flush(); } outStream.Seek(0, SeekOrigin.Begin); StreamReader streamReader = new StreamReader(outStream); string message = streamReader.ReadToEnd(); newStream = outStream; newStream.Seek(0, SeekOrigin.Begin); streamReader.Close(); } By running this, which seems to me like it would be fine, my test application gets a 400 Bad Request back from the service. If I either don't use the extension or I don't do anything in ProcessMessage everything seems fine. Any suggestions to this? As a side note, once I get this working with the generated code from the WSDL I will be moving to a WebRequest to try sending the message to the service. Currently that bombs out with a 415 Unsupported Media Type response. I'm trying to keep this post to one question but if anyone has any tips with using a WebRequest to connect to an ASMX service it would be much appreciated!

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• KeepAliveException when using HttpWebRequest.GetResponse

  - by Lucas

  I am trying to POST an attachment to CouchDB using the HttpWebRequest. However, when I attempt "response = (HttpWebResponse)httpWebRequest.GetResponse();" I receive a WebException with the message "The underlying connection was closed: A connection that was expected to be kept alive was closed by the server." I have found some articles stating that setting the keepalive to false and httpversion to 1.0 resolves the situation. I am finding that it does not yeilding the exact same error, plus I do not want to take that approach as I do not want to use the 1.0 version due to how it handles the connection. Any suggestions or ideas are welcome. I'll try them all until one works! public ServerResponse PostAttachment(Server server, Database db, Attachment attachment) { Stream dataStream; HttpWebResponse response = null; StreamReader sr = null; byte[] buffer; string json; string boundary = "----------------------------" + DateTime.Now.Ticks.ToString("x"); string headerTemplate = "Content-Disposition: form-data; name=\"_attachments\"; filename=\"" + attachment.Filename + "\"\r\n Content-Type: application/octet-stream\r\n\r\n"; byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(headerTemplate); byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n"); HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create("http://" + server.Host + ":" + server.Port.ToString() + "/" + db.Name + "/" + attachment.Document.Id); httpWebRequest.ContentType = "multipart/form-data; boundary=" + boundary; httpWebRequest.Method = "POST"; httpWebRequest.KeepAlive = true; httpWebRequest.ContentLength = attachment.Stream.Length + headerbytes.Length + boundarybytes.Length; if (!string.IsNullOrEmpty(server.EncodedCredentials)) httpWebRequest.Headers.Add("Authorization", server.EncodedCredentials); if (!attachment.Stream.CanRead) throw new System.NotSupportedException("The stream cannot be read."); // Get the request stream try { dataStream = httpWebRequest.GetRequestStream(); } catch (Exception e) { throw new WebException("Failed to get the request stream.", e); } buffer = new byte[server.BufferSize]; int bytesRead; dataStream.Write(headerbytes,0,headerbytes.Length); attachment.Stream.Position = 0; while ((bytesRead = attachment.Stream.Read(buffer, 0, buffer.Length)) > 0) { dataStream.Write(buffer, 0, bytesRead); } dataStream.Write(boundarybytes, 0, boundarybytes.Length); dataStream.Close(); // send the request and get the response try { response = (HttpWebResponse)httpWebRequest.GetResponse(); } catch (Exception e) { throw new WebException("Invalid response received from server.", e); } // get the server's response json try { dataStream = response.GetResponseStream(); sr = new StreamReader(dataStream); json = sr.ReadToEnd(); } catch (Exception e) { throw new WebException("Failed to access the response stream.", e); } // close up all our streams and response sr.Close(); dataStream.Close(); response.Close(); // Deserialize the server response return ConvertTo.JsonToServerResponse(json); }

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• Is it possible to stream a file to and from servers without holding the data in ram?

  - by Chris Denman

  Hi everyone! PHP question (new to PHP after 10 years of Perl, arrggghhh!). I have a 100mb file that I want to send to another server. I have managed to read the file in and "post" it without curl (cannot use curl for this app). Everything is working fine on smaller files. However, with the larger files, PHP complains about not being able to allocate memory. Is there a way to open a file, line by line, and send it as a post ALSO line by line? This way nothing is held in ram thus preventing my errors and getting around strict limitations. Chris

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• Query Tuning Mastery at PASS Summit 2012: The Video

  - by Adam Machanic

  An especially clever community member was kind enough to reverse-engineer the video stream for me, and came up with a direct link to the PASS TV video stream for my Query Tuning Mastery: The Art and Science of Manhandling Parallelism talk, delivered at the PASS Summit last Thursday. I'm not sure how long this link will work , but I'd like to share it for my readers who were unable to see it in person or live on the stream. Start here. Skip past the keynote, to the 149 minute mark. Enjoy!...(read more)

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• Query Tuning Mastery at PASS Summit 2012: The Video

  - by Adam Machanic

  An especially clever community member was kind enough to reverse-engineer the video stream for me, and came up with a direct link to the PASS TV video stream for my Query Tuning Mastery: The Art and Science of Manhandling Parallelism talk, delivered at the PASS Summit last Thursday. I'm not sure how long this link will work , but I'd like to share it for my readers who were unable to see it in person or live on the stream. Start here. Skip past the keynote, to the 149 minute mark. Enjoy!...(read more)

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• Embed audio broadcasting on web page

  - by giargo

  Hi, I'd like to embed simple audio player on my webpage and I want it to get the audio from a stream broadcasted from my server. I read I can use IceCast on my web-server, getting an audio stream from a client using IceS (or this is what i got from other questions and articles) but once I have my stream, IceCast is supposed to broadcast it on an URL, that can be opened from pkayers like winamp or similar. I've found out this is quite a rare topic, usually people just want to broadcast "radio" where files are taken from a static playlist. In this case I have to get a stream from an IceCast URL and embed it with a player on a web page. Thank.

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• XNA Easy Storage XBOX 360 High Scores

  - by user1003211

  To followup from a previous query - I need some help with the implementation of easystorage high scores, which is bringing up some errors on the xbox. I get the prompt screen, a savedevice is selected and a file are all created! However the file remains empty, (I've tried prepopulating but still get errors). The full portions of the scoring code can be found here: http://pastebin.com/74v897Yt The current issue in particular is in LoadHighScores() - "There is an error in XML document (0, 0)." under line data = (HighScoreData)serializer.Deserialize(stream); I'm not sure whether this line is correct either: HighScoreData data = new HighScoreData(); public static HighScoreData LoadHighScores(string container, string filename) { HighScoreData data = new HighScoreData(); if (Global.SaveDevice.FileExists(container, filename)) { Global.SaveDevice.Load(container, filename, stream => { File.Open(Global.fileName_options, FileMode.OpenOrCreate, FileAccess.Read); try { // Read the data from the file XmlSerializer serializer = new XmlSerializer(typeof(HighScoreData)); data = (HighScoreData)serializer.Deserialize(stream); } finally { // Close the file stream.Close(); // stream.Dispose(); } }); } return (data); } I call: PromptMe(); when the Start button is pressed at the beginning. I call: if (Global.SaveDevice.IsReady){entries = LoadHighScores(HighScoresContainer, HighScoresFilename);} during the menu screen to try and display the highscore screen. I call: SaveHighScore(); when game ends. I've tried altering the struct code to a class but still no luck. Any help greatly appreciated.

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• Media Streaming Server

  - by Ehsan

  I'm looking for a media stream server (specially audio streams) for installing on my Ubuntu server box. Is there any lightweight, easy configurable solution? It's awesome if this solution is able to install on a high bandwidth server and gets a stream from a low bandwidth server and serves it for many clients. (simply because the original server hasn't enough BW to serve media for many clients) (My server is a LAMP server, but I'm looking for a good solution for one of my clients to stream his audio for one hour every week)

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• How To Extract .flv Stream from JW Player 5.1?

  - by Catfish

  The problem is I've a slow internet connection, and the video doesn't buffer like in YouTube. Therefore I was wondering weather I can extract the url of the .flv file which is being streamed in JW Player and directly download it. Doing some preliminary research, I've found the following info: Main Video URL: http://ijf10.ilcannocchiale.tv/video/2263 Link Only To Video: http://ijf10.ilcannocchiale.tv/js/mediaplayer.swf?... XML File: http://ijf10.ilcannocchiale.tv/xml/video/2263 Actual File Name: 20100425_mother.flv

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• How to play a pure PCM raw stream with C#?

  - by Jader Dias

  I was looking into System.Media.SoundPlayer and NAudio, and AFAIK they only play WAVE streams. The WAVE file is composed of the pure PCM data plus a format header. I don't have this header. How to play the PCM data without the header?

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• IWebBrowser: How to specify the encoding when loading html from a stream?

  - by Ian Boyd

  Using the concepts from the sample code provided by Microsoft for loading HTML content into an IWebBrowser from an IStream using the web browser's IPersistStreamInit interface: HRESULT LoadWebBrowserFromStream(IWebBrowser* pWebBrowser, IStream* pStream) { [snip] } How can one specify the encoding of the html inside the IStream? The IStream will contain a series of bytes, but the problem is what do those bytes represent? They could, for example, contain bytes where: each byte represents a character from the current Windows code-page (e.g. 1252) each byte could represent a character from the ISO-8859-1 character set the bytes could represent UTF-8 encoded characters every 2 bytes could represent a character, using UTF-16 encoding In my particular case, i am providing the IWebBrowser an IStream that contains a series of double-bytes characters (UTF-16), but the browser (incorrectly) believes that UTF-8 encoding is in effect. This results in garbled characters.

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• FFMPEG Segfault Solutions

  - by Brentley_11

  I'm trying to convert a bunch of movies into h.264 mp4's using FFMPEG. These movies are sourced from various portable camcorders such as the Flip Mino HD and the Kodak ZI8. One issue I'm having with video from the ZI8 is it seems to be causing FFMPEG to segfault. Here is my command: ffmpeg -i 'XmasSailor720p60fps.MOV' -threads 2 -acodec libfaac -ab 96kb -vcodec libx264 -vpre hq -b 500kb -s 484x272 XmasSailor.mp4 Here is the output: FFmpeg version SVN-r20668, Copyright (c) 2000-2009 Fabrice Bellard, et al. built on Dec 2 2009 18:37:34 with gcc 4.2.4 (Ubuntu 4.2.4-1ubuntu4) configuration: --enable-libfaac --enable-libfaad --enable-libmp3lame --enable-libx264 --enable-gpl --enable-nonfree --enable-postproc --enable-pthreads --enable-shared libavutil 50. 5. 1 / 50. 5. 1 libavcodec 52.42. 0 / 52.42. 0 libavformat 52.39. 2 / 52.39. 2 libavdevice 52. 2. 0 / 52. 2. 0 libswscale 0. 7. 2 / 0. 7. 2 libpostproc 51. 2. 0 / 51. 2. 0 Seems stream 0 codec frame rate differs from container frame rate: 59.94 (60000/1001) -> 29.97 (30000/1001) Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'XmasSailor720p60fps.MOV': Duration: 00:00:05.37, start: 0.000000, bitrate: 12021 kb/s Stream #0.0(eng): Video: h264, yuv420p, 1280x720 [PAR 1:1 DAR 16:9], 11994 kb/s, 29.97 tbr, 90k tbn, 59.94 tbc Stream #0.1(eng): Audio: aac, 48000 Hz, stereo, s16, 128 kb/s Metadata major_brand : qt minor_version : 0 compatible_brands: qt comment : KODAK Zi8 Pocket Video Camera comment-eng : KODAK Zi8 Pocket Video Camera [libx264 @ 0x99e1020]using SAR=1/1 [libx264 @ 0x99e1020]using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.1 Cache64 [libx264 @ 0x99e1020]profile High, level 2.1 Output #0, mp4, to 'XmasSailor.mp4': Stream #0.0(eng): Video: libx264, yuv420p, 484x272 [PAR 1:1 DAR 121:68], q=10-51, 500 kb/s, 30k tbn, 29.97 tbc Stream #0.1(eng): Audio: aac, 48000 Hz, stereo, s16, 96 kb/s Metadata comment : Encoded with the Statusfirm Video Transcoder Stream mapping: Stream #0.0 -> #0.0 Stream #0.1 -> #0.1 Press [q] to stop encoding [h264 @ 0x99de950]B picture before any references, skipping [h264 @ 0x99de950]decode_slice_header error [h264 @ 0x99de950]no frame! Error while decoding stream #0.0 [h264 @ 0x99de950]B picture before any references, skipping [h264 @ 0x99de950]decode_slice_header error [h264 @ 0x99de950]no frame! Error while decoding stream #0.0 frame= 20 fps= 0 q=13797729.0 size= 0kB time=0.66 bitrate= 0.6kbits/s frame= 39 fps= 37 q=13797729.0 size= 0kB time=1.30 bitrate= 0.3kbits/s frame= 48 fps= 30 q=33.0 size= 11kB time=0.10 bitrate= 903.0kbits/s frame= 58 fps= 27 q=31.0 size= 22kB time=0.43 bitrate= 421.0kbits/s frame= 67 fps= 25 q=29.0 size= 41kB time=0.73 bitrate= 462.6kbits/s frame= 75 fps= 23 q=29.0 size= 59kB time=1.00 bitrate= 486.7kbits/s frame= 83 fps= 22 q=29.0 size= 81kB time=1.27 bitrate= 521.9kbits/s frame= 90 fps= 21 q=29.0 size= 97kB time=1.50 bitrate= 530.1kbits/s frame= 98 fps= 20 q=29.0 size= 114kB time=1.77 bitrate= 526.9kbits/s frame= 106 fps= 20 q=29.0 size= 134kB time=2.04 bitrate= 537.7kbits/s frame= 114 fps= 19 q=29.0 size= 150kB time=2.30 bitrate= 533.7kbits/s frame= 122 fps= 19 q=29.0 size= 172kB time=2.57 bitrate= 547.8kbits/s frame= 130 fps= 19 q=29.0 size= 193kB time=2.84 bitrate= 557.5kbits/s frame= 136 fps= 18 q=29.0 size= 211kB time=3.04 bitrate= 570.0kbits/s frame= 144 fps= 18 q=29.0 size= 242kB time=3.30 bitrate= 599.5kbits/s frame= 152 fps= 17 q=30.0 size= 261kB time=3.57 bitrate= 598.6kbits/s frame= 157 fps= 15 q=-1.0 Lsize= 368kB time=5.21 bitrate= 579.3kbits/s video:302kB audio:61kB global headers:0kB muxing overhead 1.416371% [libx264 @ 0x99e1020]frame I:1 Avg QP:27.22 size: 8720 [libx264 @ 0x99e1020]frame P:48 Avg QP:25.15 size: 3759 [libx264 @ 0x99e1020]frame B:108 Avg QP:30.10 size: 1105 [libx264 @ 0x99e1020]consecutive B-frames: 0.6% 11.5% 28.8% 59.0% [libx264 @ 0x99e1020]mb I I16..4: 28.5% 47.6% 23.9% [libx264 @ 0x99e1020]mb P I16..4: 0.8% 1.3% 0.5% P16..4: 50.6% 17.7% 13.1% 0.0% 0.0% skip:15.9% [libx264 @ 0x99e1020]mb B I16..4: 0.2% 0.3% 0.1% B16..8: 44.0% 1.2% 2.6% direct: 5.1% skip:46.5% L0:45.5% L1:51.0% BI: 3.5% [libx264 @ 0x99e1020]final ratefactor: 23.51 [libx264 @ 0x99e1020]8x8 transform intra:49.9% inter:67.9% [libx264 @ 0x99e1020]direct mvs spatial:98.1% temporal:1.9% [libx264 @ 0x99e1020]coded y,uvDC,uvAC intra: 54.7% 76.1% 41.4% inter: 17.1% 24.4% 7.8% [libx264 @ 0x99e1020]i16 v,h,dc,p: 18% 52% 5% 25% [libx264 @ 0x99e1020]i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 12% 22% 9% 7% 10% 10% 9% 8% 13% [libx264 @ 0x99e1020]i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 13% 18% 8% 8% 10% 13% 10% 9% 12% [libx264 @ 0x99e1020]Weighted P-Frames: Y:10.4% [libx264 @ 0x99e1020]ref P L0: 60.2% 15.3% 11.0% 7.6% 5.2% 0.7% [libx264 @ 0x99e1020]ref B L0: 72.6% 15.6% 11.8% [libx264 @ 0x99e1020]kb/s:471.17 Segmentation fault I'm wondering if anyone else has ran into similar issues. I wasn't able to find anything helpful via Google. Another question I have is if anyone knows of a company that offers paid support for FFMPEG. Thank you for your time.

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• Changes to the LINQ-to-StreamInsight Dialect

  - by Roman Schindlauer

  In previous versions of StreamInsight (1.0 through 2.0), CepStream<> represents temporal streams of many varieties: Streams with ‘open’ inputs (e.g., those defined and composed over CepStream<T>.Create(string streamName) Streams with ‘partially bound’ inputs (e.g., those defined and composed over CepStream<T>.Create(Type adapterFactory, …)) Streams with fully bound inputs (e.g., those defined and composed over To*Stream – sequences or DQC) The stream may be embedded (where Server.Create is used) The stream may be remote (where Server.Connect is used) When adding support for new programming primitives in StreamInsight 2.1, we faced a choice: Add a fourth variety (use CepStream<> to represent streams that are bound the new programming model constructs), or introduce a separate type that represents temporal streams in the new user model. We opted for the latter. Introducing a new type has the effect of reducing the number of (confusing) runtime failures due to inappropriate uses of CepStream<> instances in the incorrect context. The new types are: IStreamable<>, which logically represents a temporal stream. IQStreamable<> : IStreamable<>, which represents a queryable temporal stream. Its relationship to IStreamable<> is analogous to the relationship of IQueryable<> to IEnumerable<>. The developer can compose temporal queries over remote stream sources using this type. The syntax of temporal queries composed over IQStreamable<> is mostly consistent with the syntax of our existing CepStream<>-based LINQ provider. However, we have taken the opportunity to refine certain aspects of the language surface. Differences are outlined below. Because 2.1 introduces new types to represent temporal queries, the changes outlined in this post do no impact existing StreamInsight applications using the existing types! SelectMany StreamInsight does not support the SelectMany operator in its usual form (which is analogous to SQL’s “CROSS APPLY” operator): static IEnumerable<R> SelectMany<T, R>(this IEnumerable<T> source, Func<T, IEnumerable<R>> collectionSelector) It instead uses SelectMany as a convenient syntactic representation of an inner join. The parameter to the selector function is thus unavailable. Because the parameter isn’t supported, its type in StreamInsight 1.0 – 2.0 wasn’t carefully scrutinized. Unfortunately, the type chosen for the parameter is nonsensical to LINQ programmers: static CepStream<R> SelectMany<T, R>(this CepStream<T> source, Expression<Func<CepStream<T>, CepStream<R>>> streamSelector) Using Unit as the type for the parameter accurately reflects the StreamInsight’s capabilities: static IQStreamable<R> SelectMany<T, R>(this IQStreamable<T> source, Expression<Func<Unit, IQStreamable<R>>> streamSelector) For queries that succeed – that is, queries that do not reference the stream selector parameter – there is no difference between the code written for the two overloads: from x in xs from y in ys select f(x, y) Top-K The Take operator used in StreamInsight causes confusion for LINQ programmers because it is applied to the (unbounded) stream rather than the (bounded) window, suggesting that the query as a whole will return k rows: (from win in xs.SnapshotWindow() from x in win orderby x.A select x.B).Take(k) The use of SelectMany is also unfortunate in this context because it implies the availability of the window parameter within the remainder of the comprehension. The following compiles but fails at runtime: (from win in xs.SnapshotWindow() from x in win orderby x.A select win).Take(k) The Take operator in 2.1 is applied to the window rather than the stream: Before After (from win in xs.SnapshotWindow() from x in win orderby x.A select x.B).Take(k) from win in xs.SnapshotWindow() from b in     (from x in win     orderby x.A     select x.B).Take(k) select b Multicast We are introducing an explicit multicast operator in order to preserve expression identity, which is important given the semantics about moving code to and from StreamInsight. This also better matches existing LINQ dialects, such as Reactive. This pattern enables expressing multicasting in two ways: Implicit Explicit var ys = from x in xs          where x.A > 1          select x; var zs = from y1 in ys          from y2 in ys.ShiftEventTime(_ => TimeSpan.FromSeconds(1))          select y1 + y2; var ys = from x in xs          where x.A > 1          select x; var zs = ys.Multicast(ys1 =>     from y1 in ys1     from y2 in ys1.ShiftEventTime(_ => TimeSpan.FromSeconds(1))     select y1 + y2; Notice the product translates an expression using implicit multicast into an expression using the explicit multicast operator. The user does not see this translation. Default window policies Only default window policies are supported in the new surface. Other policies can be simulated by using AlterEventLifetime. Before After xs.SnapshotWindow(     WindowInputPolicy.ClipToWindow,     SnapshotWindowInputPolicy.Clip) xs.SnapshotWindow() xs.TumblingWindow(     TimeSpan.FromSeconds(1),     HoppingWindowOutputPolicy.PointAlignToWindowEnd) xs.TumblingWindow(     TimeSpan.FromSeconds(1)) xs.TumblingWindow(     TimeSpan.FromSeconds(1),     HoppingWindowOutputPolicy.ClipToWindowEnd) Not supported … LeftAntiJoin Representation of LASJ as a correlated sub-query in the LINQ surface is problematic as the StreamInsight engine does not support correlated sub-queries (see discussion of SelectMany). The current syntax requires the introduction of an otherwise unsupported ‘IsEmpty()’ operator. As a result, the pattern is not discoverable and implies capabilities not present in the server. The direct representation of LASJ is used instead: Before After from x in xs where     (from y in ys     where x.A > y.B     select y).IsEmpty() select x xs.LeftAntiJoin(ys, (x, y) => x.A > y.B) from x in xs where     (from y in ys     where x.A == y.B     select y).IsEmpty() select x xs.LeftAntiJoin(ys, x => x.A, y => y.B) ApplyWithUnion The ApplyWithUnion methods have been deprecated since their signatures are redundant given the standard SelectMany overloads: Before After xs.GroupBy(x => x.A).ApplyWithUnion(gs => from win in gs.SnapshotWindow() select win.Count()) xs.GroupBy(x => x.A).SelectMany(     gs =>     from win in gs.SnapshotWindow()     select win.Count()) xs.GroupBy(x => x.A).ApplyWithUnion(gs => from win in gs.SnapshotWindow() select win.Count(), r => new { r.Key, Count = r.Payload }) from x in xs group x by x.A into gs from win in gs.SnapshotWindow() select new { gs.Key, Count = win.Count() } Alternate UDO syntax The representation of UDOs in the StreamInsight LINQ dialect confuses cardinalities. Based on the semantics of user-defined operators in StreamInsight, one would expect to construct queries in the following form: from win in xs.SnapshotWindow() from y in MyUdo(win) select y Instead, the UDO proxy method is referenced within a projection, and the (many) results returned by the user code are automatically flattened into a stream: from win in xs.SnapshotWindow() select MyUdo(win) The “many-or-one” confusion is exemplified by the following example that compiles but fails at runtime: from win in xs.SnapshotWindow() select MyUdo(win) + win.Count() The above query must fail because the UDO is in fact returning many values per window while the count aggregate is returning one. Original syntax New alternate syntax from win in xs.SnapshotWindow() select win.UdoProxy(1) from win in xs.SnapshotWindow() from y in win.UserDefinedOperator(() => new Udo(1)) select y -or- from win in xs.SnapshotWindow() from y in win.UdoMacro(1) select y Notice that this formulation also sidesteps the dynamic type pitfalls of the existing “proxy method” approach to UDOs, in which the type of the UDO implementation (TInput, TOuput) and the type of its constructor arguments (TConfig) need to align in a precise and non-obvious way with the argument and return types for the corresponding proxy method. UDSO syntax UDSO currently leverages the DataContractSerializer to clone initial state for logical instances of the user operator. Initial state will instead be described by an expression in the new LINQ surface. Before After xs.Scan(new Udso()) xs.Scan(() => new Udso()) Name changes ShiftEventTime => AlterEventStartTime: The alter event lifetime overload taking a new start time value has been renamed. CountByStartTimeWindow => CountWindow

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• Facebook Connect Publish to Stream: how do I tag a user?

  - by Sean Cannon

  I have an application that allows martial arts trickers to 'battle' each other by initiating challenges and submitting videos and whatnot. When user A challenges user B, the application posts to the user's wall (the one who initiated the challenge). My question is how do I tag user B in the wall post? It essentially says "challenged John Do to a battle". I'd like "John Do" to link to his profile just like when you manually post something on your wall and use the @ symbol. I hope this makes sense. I've tried standard html for a link, and I've tried FBML. Neither are parsed and only render as plain text on the wall post. Thanks for any help!

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• How to trace a raw (character) device stream on Unix ?

  - by Fabien

  I'm trying to trace what is transiting in a raw (character) device on an Unix system (ex: /dev/tty.baseband) for DEBUG purpose. I am thinking of creating a deamon that would: upon start rename /dev/tty.baseband to /dev/tty.baseband.old. create a raw node /dev/tty.baseband spawn two threads: Thread 1: reading /dev/tty.baseband.old writing into /dev/tty.baseband Thread 2: reading /dev/tty.baseband writing into /dev/tty.baseband.old This would work a little bit like a MITM process. I wonder if there is not a 'standard' way to do this.

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• How can I decompress a gzip stream with zlib?

  - by Greg Hewgill

  Gzip format files (created with the gzip program, for example) use the "deflate" compression algorithm, which is the same compression algorithm as what zlib uses. However, when using zlib to inflate a gzip compressed file, the library returns a Z_DATA_ERROR. How can I use zlib to decompress a gzip file?

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• What HTTP headers do I need to stream an ASF file?

  - by SoaperGEM

  I have a simple PHP script that will either serve up a streaming ASF file or not, depending on whether you're logged in and have access to the file. It basically does this: <?php header('Content-Type: video/x-ms-asf'); header('Content-Disposition: inline; filename="file.asf"'); readfile('file.asf'); ?> This already works fine in Firefox; when you navigate to this file it starts the video streaming right away. But Internet Explorer is a different story. When I go to this link in IE, it consistently tries to download the file as if it were an attachment rather than streaming it in the browser. What I am missing that IE's getting hung up on?

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• How does Bitmap.Save(Stream, ImageFormat) format the data?

  - by Matt Jacobsen

  I have a non transparent, colour bitmap with length 2480 and width 3507. Using Bitmap.GetPixel(int x, int y) I am able to get the colour information of each pixel in the bitmap. If I squirt the bitmap into a byte[]: MemoryStream ms = new MemoryStream(); bmp.Save(ms, ImageFormat.Bmp); ms.Position = 0; byte[] bytes = ms.ToArray(); then I'd expect to have the same information, i.e. I can go to bytes[1000] and read the colour information for that pixel. It turns out that my array of bytes is larger than I anticipated. I thought I'd get an array with 2480 x 3507 = 8697360 elements. Instead I get an array with 8698438 elements - some sort of header I presume. In what format the bytes in my array stored? Is there a header 1078 bytes long followed by Alpha, Red, Green, Blue values for every byte element, or something else?

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