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• Use FFMPEG to stream images from one client to another through IIS (or other) server

  20 avril 2012, par eselk

  I'm new to FFMPEG and maybe I should post this in their forums, but you guys here seem to know everything, so here goes. I have a client app that takes screen shots and saves them as images (256 color bitmaps currently, can change if needed), it does this at a rate of about 4 fps. I currently use my own socket code written in C# to push these to my socket server (also C#) running on a Windows 2008 server. That server then sends these images out to several clients that display them as they are received and also buffers them to allow for rewind, pause, etc, like a DVR. My current format requires approx 100KB per frame, and thus only works for a very small number of clients.

  I started looking at FFMPEG and the compression with MPEG1 and especially MPEG4 is amazing, and so is the quality. What I'm looking for is a basic guide, tutorial, or steps, to produce something similar to my current design, but using FFMPEG and actual video streaming. Ideally the player side could be something like Flash or anything that is easy to embed in a .NET WinForm (or a browser control I can host in the WinForm), and it would need to support buffering still so they can pause and rewind (about 5 or 10 mins, which seems like a lot, but remember this is only 4 fps and 256 color, about 1 or 2 MB per min in my testing).

  I see that FFMPEG, the command-line utility, and I assume the API, even has options for posting to a server via UDP or TCP, so maybe I'll use that instead of my own socket code. Ideally my app would feed images to FFMPEG library at a rate of 4fps as they come from the screen-shot unit, and it would send these up to my IIS server (or another server ?) which would then server them to client(s) that could use them similar to a YouTube video.

• Node.js Live Streaming : Avoid buffering

  27 octobre 2012, par Shirish Kamath

  I've written a small nodeJS server that outputs system audio captured by ffmpeg on Windows (using DirectShow) to the browser as a streaming MP3 file. The audio needs to be as live as possible, with minimum/no buffering, and a "skipping" effect in the audio is perfectly acceptable.

  When I play the audio in Chrome using the HTML5 audio tag, there's a delay of about 8-10 secs over a low-latency LAN connection. I suspected this to be a client-side buffer, and used a Flash MP3 player on the client-side, which brought down the delay to 2-3 secs.

  Now, the buffering seems to taking place on the server-side. The documentation for NodeJS's response.write mentions that the data is written kernel buffers. How do I go about avoiding any buffering altogether or at least getting around it, so that the client always gets the latest audio data ? Strategies for handling 'drain' events to always push live data ?

  On the request object, I've used setNoDelay(true) to avoid the use of Nagle's algorithm. Following is a snippet of how data is written when the spawned ffmpeg process emits data.

  var clients = []; //List of client connections currently being served
  
  ffmpeg.stdout.on('data', function(data) {
  
      for(var i = 0; i < clients.length; i++){
  
          clients[i].res.write(data);
  
      }
  
  });

• Correcting color cast with ffmpeg

  16 mai 2018, par Henry H

  I have two videos that have a pretty significant blue cast to them. I took some stills at the same time and I’m happy enough with the colors on those and I’d like to re-encode the videos, adjusting the colors to something similar to the stills.

  • A frame from the original video can be seen here : http://www.dotrose.com/temp/img_20180513_153484_original.png
  • An attempt at correcting the color, which would be acceptable : http://www.dotrose.com/temp/img_20180513_153484_corrected.png
  • A still image taken at the same time (but with some help from a flash) : http://www.dotrose.com/temp/img_20180513_153476.jpg

  I understand I could either create a large collection of jpg images from the video and color correct them before reassembling them into a new video or I could use ffmpeg’s color level’s filter to do it directly. What I don’t know is how to get the numbers to pass to the filter. I’m assuming I want to do something like this :

  ffmpeg -i video.mov -vf "colorlevels=rimin=##/255:gimin=##/255:bimin=#/255:rimax=###/255:gimax=###/255:bimax=###/255, eq=gamma=#.##" -y out.mov

  How do I get the values to use for each of the r, g, and b min and max settings and gamma to use in place of the ###s ? Assuming this is the right approach, of course.

  Update : Perhaps this question would be better asked in a forum for gimp or photoshop. But I know how to adjust the color in those. What I need to know is how I translate those changes to what ffmpeg is expecting.