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• Architecture of video-based service for mobile phones

  27 juin 2015, par David Azar

  I guess this is more of a conceptual question than a technical one.

  I’m trying to figure out the best way to upload short videos to a server and also be able to download them and watch them on both Android and iOS.

  Lets focus on Android for the moment.

  I’ve done some experiments, and my results have been :

  • I’m able to compress 12-14MB video down to 500KB using FFMPEG lib with pretty good results in quality, but it takes about 12 seconds.

  • Next, im uploading those videos to my Parse backend as ParseFile to store them.

  • Finally, i can download them and watch them with no problem using a VideoView widget.

  Now, for the tests i’ve been running, these are great results. But i want to see if there is a better way to manage and scale all of this.

  My questions are :

  • Is there a better, lighter way to compress video ?

  • Is Parse the right way to go ?

  • How can i stream videos instead of downloading them and storing the on local storage before playing them ? i know this will cause my app to use significant space on disk and i dont want that.

  • How do big companies do this kind of tasks ?

  I’ve heard Amazon S3 is a cool thing for projects like this one, also Google Cloud Platform. I want to understand the best approach before building everything so i can do it the right way and also, provide the absolute best user experience for watching these videos.

• Create mp4 thumbnail in node.js

  21 mai 2015, par trdavidson

  new in node.js and aws framework so I apologize in advance. I am trying to configure the AWS DB of my app to automatically create thumbnails using AWS Lambda. This works great using the example provided by Amazon for regular .jpg images (walkthrough here : https://alestic.com/2014/11/aws-lambda-cli/).

  However to try and do the same operation for mp4 files seems exponentially more difficult. After some searching I found that it seems the way to do this is by using the ffmpeg module. The problem is that I do not at all understand the response object returned by aws, and thus am not sure how to manipulate it so that ffmpeg can use it.

  current code :

  // dependencies
  
  var async = require('async');
  
  var AWS = require('aws-sdk');
  
  var gm = require('gm')
  
              .subClass({ imageMagick: true }); // Enable ImageMagick integration.
  
  var util = require('util');
  
  var ffmpeg = require('ffmpeg');
  
  var stream = require('stream')
  
  
  
  // constants
  
  var MAX_WIDTH  = 250;
  
  var MAX_HEIGHT = 250;
  
  
  
  // get reference to S3 client 
  
  var s3 = new AWS.S3();
  
  
  
  exports.handler = function(event, context) {
  
      // Read options from the event.
  
      console.log("Reading options from event:\n", util.inspect(event, {depth: 5}));
  
      var srcBucket = event.Records[0].s3.bucket.name;
  
      // Object key may have spaces or unicode non-ASCII characters.
  
      var srcKey    =
  
      decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, " "));  
  
      var dstBucket = srcBucket + "small";
  
      var dstKey    = "small-" + srcKey;
  
  // Sanity check: validate that source and destination are different buckets.
  
  if (srcBucket == dstBucket) {
  
      console.error("Destination bucket must not match source bucket.");
  
      return;
  
  }
  
  
  
  // Infer the image type.
  
  var typeMatch = srcKey.match(/\.([^.]*)$/);
  
  if (!typeMatch) {
  
      console.error('unable to infer image type for key ' + srcKey);
  
      return;
  
  }
  
  var imageType = typeMatch[1];
  
  if (imageType != "mp4" && imageType != "avi") {
  
      console.log('skipping non-image ' + srcKey);
  
      return;
  
  }
  
  
  
  // Download the image from S3, transform, and upload to a different S3 bucket.
  
  async.waterfall([
  
      function download(next) {
  
          // Download the image from S3 into a buffer.
  
  
  
          s3.getObject({
  
                  Bucket: srcBucket,
  
                  Key: srcKey
  
              },
  
              next);
  
          },
  
      function tranform(response, next) {
  
          var instream = new stream.Readable();
  
          instream.push(response.Body)
  
          instream.push(null)
  
  
  
          var outstream = new stream();
  
  
  
          ffmpeg(instream)
  
          .screenshots({timestamps: 1, size: '200x200'})
  
          .output('screenshot.png')
  
          .output(outstream)
  
          .on('end', function(){
  
              console.log('screenshots finished processing son!')
  
          })
  
  
  
          gm(outstream, 'screenshot.png').size(function(err, size) {
  
              // Infer the scaling factor to avoid stretching the image unnaturally.
  
              var scalingFactor = Math.min(
  
                  MAX_WIDTH / size.width,
  
                  MAX_HEIGHT / size.height
  
              );
  
              var width  = scalingFactor * size.width;
  
              var height = scalingFactor * size.height;
  
  
  
              // Transform the image buffer in memory.
  
              this.resize(width, height)
  
                  .toBuffer(imageType, function(err, buffer) {
  
                      if (err) {
  
                          next(err);
  
                      } else {
  
                          next(null, response.ContentType, buffer);
  
                      }
  
                  });
  
          });
  
      },
  
      function upload(contentType, data, next) {
  
          // Stream the transformed image to a different S3 bucket.
  
          s3.putObject({
  
                  Bucket: dstBucket,
  
                  Key: dstKey,
  
                  Body: data,
  
                  ContentType: contentType
  
              },
  
              next);
  
          }
  
      ], function (err) {
  
          if (err) {
  
              console.error(
  
                  'Unable to resize ' + srcBucket + '/' + srcKey +
  
                  ' and upload to ' + dstBucket + '/' + dstKey +
  
                  ' due to an error: ' + err
  
              );
  
          } else {
  
              console.log(
  
                  'Successfully resized ' + srcBucket + '/' + srcKey +
  
                  ' and uploaded to ' + dstBucket + '/' + dstKey
  
              );
  
          }
  
  
  
          context.done();
  
      }
  
  );

  } ;

  Any suggestions are welcome ! Thanks

• Trying to grab video stream from a 802W device

  1er juin 2015, par brentil

  A group of us in the RC hobby forums had started trying to use a device called the 802W, it takes RCA in and then broadcasts it back out over a WiFi you connect to via an Android or iOS device. They’re typically used for backup camera addon systems for vehicles. We want to use it to do FPV (First Person Video/View) with using smartphones instead of buying more expensive FPV goggles.

  802W device example (plenty of clones online)

  http://www.amazon.com/Wireless-Backup-Camera-Transmitter-Android/dp/B00LJPTJSY

  The problem is you can only use their application WIFI_AVIN or WIFI_AVIN2 from the app stores to connect to it because they don’t publish the information about how to grab the stream data. We want to write our own apps that can use the stream to better show the information. We’ve tried using VLC to grab the stream from an Android phone or a Windows PC but we’ve had no success so far. I was hoping someone could look at the Wireshark outputs and might understand what they’re looking at better than I am. I "think" it’s a UDP multicast being broadcasted but I just don’t know enough to be sure. We’ve tried using VLC to connect to network streams directly on the device or from udp ://@ type addresses but I think part of the issue too might be we’re missing the file path of the stream file.

  Attempting to reverse engineer their code for learning purposes showed that ffmpeg is inside a compiled .so library which also seems to be where the actual connection code happens which we were unable to dig into.

  In the images 192.168.72.33 is my phone and 192.168.72.173 is the 802W device.

  Image of what I believe is a UDP broadcast of the video information.
  

  This is what the stream turns into when the device connects using the WIFI_AVIN application.