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• Dreamcast Track Sizes

  1er mars 2015, par Multimedia Mike — Sega Dreamcast

  I’ve been playing around with Sega Dreamcast discs lately. Not playing the games on the DC discs, of course, just studying their structure. To review, the Sega Dreamcast game console used special optical discs named GD-ROMs, where the GD stands for “gigadisc”. They are capable of holding about 1 gigabyte of data.

  You know what’s weird about these discs ? Each one manages to actually store a gigabyte of data. Each disc has a CD portion and a GD portion. The CD portion occupies the first 45000 sectors and can be read in any standard CD drive. This area is divided between a brief data track and a brief (usually) audio track.

  The GD region starts at sector 45000. Sometimes, it’s just one humongous data track that consumes the entire GD region. More often, however, the data track is split between the first track and the last track in the region and there are 1 or more audio tracks in between. But the weird thing is, the GD region is always full. I made a study of it (click for a larger, interactive graph) :

  
  
  

  Some discs put special data or audio bonuses in the CD region for players to discover. But every disc manages to fill out the GD region. I checked up on a lot of those audio tracks that divide the GD data and they’re legitimate music tracks. So what’s the motivation ? Why would the data track be split in 2 pieces like that ?

  I eventually realized that I probably answered this question in this blog post from 4 years ago. The read speed from the outside of an optical disc is higher than the inside of the same disc. When I inspect the outer data tracks of some of these discs, sure enough, there seem to be timing-sensitive multimedia FMV files living on the outer stretches.

  One day, I’ll write a utility to take apart the split ISO-9660 filesystem offset from a weird sector.

• fail continuous transfer video file into buffer

  9 décembre 2016, par chintitomasud

  here I want to process a video file transcoding on demand by using ffmpeg but I failed. without ffmpeg all code runs properly. but using ffmpeg I face some problem. it shows this message :

  Spawning new process /samiul113039/1080.mp4:GET
  piping ffmpeg output to client, pid 10016
  HTTP connection disrupted, killing ffmpeg : 10016
  Spawning new process /samiul113039/1080.mp4:GET
  piping ffmpeg output to client, pid 4796
  HTTP connection disrupted, killing ffmpeg : 4796
  ffmpeg didn’t quit on q, sending signals
  ffmpeg has exited : 10016, code null
  ffmpeg didn’t quit on q, sending signals
  ffmpeg has exited : 4796, code nul
  

  var fs=require('fs');
  
  
  
  var url=require("url");
  
  var urlvalue="http://csestudents.uiu.ac.bd/samiul113039/1080.mp4";
  
  
  
  
  
  var parseurl=url.parse(urlvalue);
  
  
  
  var HDHomeRunIP = parseurl.hostname;
  
  var HDHomeRunPort = parseurl.port;
  
  var childKillTimeoutMs = 1000;
  
  
  
  var parseArgs = require('minimist')(process.argv.slice(2));
  
  
  
  // define startsWith for string
  
  if (typeof String.prototype.startsWith != 'function') {
  
    // see below for better implementation!
  
    String.prototype.startsWith = function (str){
  
      return this.indexOf(str) == 0;
  
    };
  
  }
  
  // Called when the response object fires the 'close' handler, kills ffmpeg 
  
  function responseCloseHandler(command) {
  
    if (command.exited != true) {
  
      console.log('HTTP connection disrupted, killing ffmpeg: ' + command.pid);
  
      // Send a 'q' which signals ffmpeg to quit. 
  
      // Then wait half a second, send a nice signal, wait another half second
  
      // and send SIGKILL
  
      command.stdin.write('q\n');
  
      command.stdin.destroy();
  
      // install timeout and wait
  
      setTimeout(function() {
  
        if (command.exited != true) {
  
          console.log('ffmpeg didn\'t quit on q, sending signals');
  
          // still connected, do safe sig kills
  
          command.kill();
  
          try { 
  
            command.kill('SIGQUIT');
  
          } catch (err) {}
  
          try {
  
            command.kill('SIGINT');
  
          } catch (err) {} 
  
          // wait some more!
  
          setTimeout(function() {
  
            if (command.exited != true) {
  
              console.log('ffmpeg didn\'t quit on signals, sending SIGKILL');
  
              // at this point, just give up and whack it
  
              try {
  
                command.kill('SIGKILL');
  
              } catch (err) {}
  
            }
  
          }, childKillTimeoutMs);
  
        }    
  
      }, childKillTimeoutMs);
  
    }
  
  }
  
  
  
  // Performs a proxy. Copies data from proxy_request into response
  
  function doProxy(request,response,http,options) {
  
    var proxy_request = http.request(options, function (proxy_response) {
  
      proxy_response.on('data', function(chunk) {
  
        response.write(chunk, 'binary');
  
      });
  
      proxy_response.on('end', function() {
  
        response.end();
  
      });
  
      response.writeHead(proxy_response.statusCode, proxy_response.headers);
  
    });
  
    request.on('data', function(chunk) {
  
      proxy_request.write(chunk, 'binary');
  
    });
  
    // error handler
  
    proxy_request.on('error', function(e) {
  
      console.log('problem with request: ' + e.message);
  
      response.writeHeader(500);
  
      response.end();
  
    });
  
  
  
    proxy_request.end();
  
  }
  
  
  
  var child_process = require('child_process');
  
  var auth = require('./auth');
  
  // Performs the transcoding after the URL is validated
  
  function doTranscode(request,response) {
  
    //res.setHeader("Accept-Ranges", "bytes");
  
    response.setHeader("Accept-Ranges", "bytes");
  
    response.setHeader("Content-Type", "video/mp4");        
  
    response.setHeader("Connection","close");
  
    response.setHeader("Cache-Control","no-cache");
  
    response.setHeader("Pragma","no-cache");
  
  
  
    // always write the header
  
    response.writeHeader(200);
  
  
  
    // if get, spawn command stream it
  
    if (request.method == 'GET') {
  
      console.log('Spawning new process ' + request.url + ":" + request.method);
  
  
  
  var command = child_process.spawn('ffmpeg', 
  
                                        ['-i','http://csestudents.uiu.ac.bd/samiul113039/1080.mp4','-f','mpegts','-'],
  
                                        { stdio: ['pipe','pipe','ignore'] }); 
  
  
  
       command.exited = false;
  
      // handler for when ffmpeg dies unexpectedly
  
      command.on('exit',function(code,signal) {
  
        console.log('ffmpeg has exited: ' + command.pid + ", code " + code);
  
        // set flag saying we've quit
  
        command.exited = true;
  
        response.end();
  
      });
  
      command.on('error',function(error) {
  
        console.log('ffmpeg error handler - unable to kill: ' + command.pid);
  
        // on well, might as well give up
  
        command.exited = true;
  
        try {
  
          command.stdin.close(); 
  
        } catch (err) {}
  
        try {
  
          command.stdout.close();
  
        } catch (err) {}
  
        try {
  
          command.stderr.close();
  
        } catch (err) {}
  
        response.end();
  
      });
  
      // handler for when client closes the URL connection - stop ffmpeg
  
      response.on('end',function() { 
  
       responseCloseHandler(command);
  
      });
  
      // handler for when client closes the URL connection - stop ffmpeg
  
      response.on('close',function() { 
  
        responseCloseHandler(command); 
  
      });
  
  
  
      // now stream
  
      console.log('piping ffmpeg output to client, pid ' + command.pid);
  
      command.stdout.pipe(response);
  
      command.stdin.on('error',function(err) {
  
        console.log("Weird error in stdin pipe ", err);
  
        response.end();
  
      });
  
      command.stdout.on('error',function(err) {
  
        console.log("Weird error in stdout pipe ",err);
  
        response.end();
  
      });
  
    } 
  
    else {
  
      // not GET, so close response
  
      response.end();
  
    }
  
  }
  
  
  
  // Load the http module to create an http server.
  
  var http = require('http');
  
  
  
  // Configure our HTTP server to respond with Hello World to all requests.
  
  var server = http.createServer(function (request, response) {
  
    //console.log("New connection from " + request.socket.remoteAddress + ":" + request.url);
  
  
  
    if (auth.validate(request,response)) {
  
      // first send a HEAD request to our HD Home Run with the same url to see if the address is valid.
  
      // This prevents an ffmpeg instance to spawn when clients request invalid things - like robots.txt/etc
  
      var options = {method: 'HEAD', hostname: HDHomeRunIP, port: HDHomeRunPort, path: request.url};
  
      var req = http.request(options, function(res) {
  
        // if they do a get, and it returns good status
  
        if (request.method == "GET" &&
  
            res.statusCode == 200 &&
  
            res.headers["content-type"] != null &&
  
            res.headers["content-type"].startsWith("video")) {
  
          // transcode is possible, start it now!
  
          doTranscode(request,response);
  
        } 
  
        else {
  
          // no video or error, cannot transcode, just forward the response from the HD Home run to the client
  
          if (request.method == "HEAD") {
  
            response.writeHead(res.statusCode,res.headers);
  
            response.end();
  
          }
  
          else {
  
            // do a 301 redirect and have the device response directly  
  
  
  
            // just proxy it, that way browser doesn't redirect to HDHomeRun IP but keeps the node.js server IP
  
            options = {method: request.method, hostname: HDHomeRunIP, /* port: HDHomeRunPort, */path: request.url};
  
            doProxy(request,response,http,options);
  
          }
  
        }
  
      });
  
      req.on('error', function(e) {
  
        console.log('problem with request: ' + e.message);
  
        response.writeHeader(500);
  
        response.end();
  
      });
  
      // finish the client request, rest of processing done in the async callbacks
  
      req.end();
  
    }
  
  });
  
  
  
  // turn on no delay for tcp
  
  server.on('connection', function (socket) {
  
    socket.setNoDelay(true);
  
  });
  
  server.listen(7000);

• How to use the information from ffprobe to use with ffmpeg. Is there a shortcut to the syntax ?

  20 novembre 2016, par Margaret Montreux

  Want to batch convert a bunch of different video files from cli instead of Rolands old-and-slow-drag-and-drop-one-file-at-a-time-software. I have used ffprobe in OS X Terminal here. This shows us what the software did to the file and I want to do the same. MJPEG AVI I get but the rest, how would my ffmpeg syntax look to achieve this result efter converting ?

  Example : My ffprobe give me this

  Input #0, avi, from 'P10_0001.AVI':
Metadata:
comment :
encoder : Roland Corporation
Duration: 00:03:17.64, start: 0.000000, bitrate: 16694 kb/s
Stream #0:0: Video: mjpeg (MJPG / 0x47504A4D), yuvj422p(pc, bt470bg/unknown/unknown), 640x480, 15285 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 2 channels, s16, 1411 kb/s

  What would the ffmpeg syntax look like to do this with a new file.

  I’ve been trying some simple ones but those are not accepted by the machine (Edirol p-10) and I hope someone can point me in the right direction. :)

  Edit :
  OK. The syntax I want to do is involving 3 files.

  1. File that has the correct codec and everything to work with the machine. P10_0001.AVI

  2. A file that does not have the correct format (codec etc.) softvision.mpg

  3. A new file just as file 2 but with the codec of file number 1. P10_0002.AVI