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• Android Recorded Video Compression

  28 juillet 2014, par Nick Babenko

  This is a fairly long-winded issue and I’ve tried a couple of methods to fix it.

  The ultimate problem is the user records a video and the video is to be uploaded via a REST API. The original solution was to use the camera app and pass the user though via an Intent. This method requires very little configuration for video optimisation - using the MediaStore.EXTRA_VIDEO_QUALITY and value of 0 gives MMS optimisation, which makes the videos pretty much unusable and I was hoping for something a little more around 480p.

  So I started to create a custom video recorder using the MediaRecorder class. I managed to get this to work fine on a Nexus 4. I have 2 other test devices, a ZTE Blade and an Acer Iconica tab and it didn’t work with either of these devices.
  The ZTE Blade complained about an incorrect video size but the video size I was using was given by Camera.Parameters.getSupportedVideoSizes.
  The Acer Iconica tab didn’t have any valid CamcorderProfile’s. Calling CamcorderProfile.hasProfile on all of the available CamcorderProfile constants returned false. So if I was unsuccessful at loading a CamcorderProfile I attempted to configure MediaRecorder manually based on a device profile I found. This worked to an extent, but when I pressed record, I was presented with a black screen.

  The second solution was to use the existing camera intent solution, but then compress the video using FFMPEG. My experience of using the Android NDK is nil, so it was a bit of a challenge. I managed to compile a library which interfaces natively with FFMEG - this one specifically (https://github.com/Batterii/android-ffmpeg-x264). The Videokit class initialises, but when it comes to calling run with the following arguments :

  videoKit.run(new String[] {"ffmpeg", "-i", file.getAbsolutePath(), "-vf",
                       "scale=-1:480", "-vcodec", "mp3g4", "-qscale", "3",
                       outputFile.getAbsolutePath()});

  The app suddenly stops with no exception and almost nothing in the logs except that the activity suddenly stopped.

  The ultimate question I’ve been getting to is wether anyone has any solution to compress a video recorded on an Android device. If anyone can add to any of the issues I mentioned which hopefully will fix the issue, but I can’t quite get working then I will appreciate that even more.

  Thanks for reading and any help anyone has is incredibly appreciated.

• How to implement transitions in Video created via ffmpeg

  4 septembre 2014, par unkn0wn

  Hello all i a trying to create a video using couple of images and texts. Till now i have been successfully converted images into video. But they look too boring. Here’s what i used.

  //FAde OUT AND FADE IN
  
  
  
  ffmpeg -loop 1 -i input0.png -loop 1 -i input1.png -filter_complex "[1:v][0:v]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'" -t 4 frames.mp4
  
  
  
  //Text over a video
  
  ffmpeg -t 10 -loop 1 -i q003.jpg -i a002.mp3  -vf drawtext="fontfile=m1.ttf:text=t:fontsize=20:fontcolor=white:x=main_w-40*(t-5)*(t-5):y=main_h/2-text_h/2" -acodec copy -c:v libx264 -c:a aac -strict experimental  -b:a 192k -shortest out.mp4

  But i could find any better documentation to read from. how can i implement more animations and transition effects to my video ?

  For reference kindly see animoto.com.

• Set content-length when converting video stream to audio (w/ FFMPEG & Node.js)

  15 septembre 2014, par Taconut

  So I’m building a program that requires that I take a video and convert it to audio. I’m currently streaming the audio directly to the browser via node.js, but I’ve run into a major problem : I don’t know how to find out how many bytes my audio is. As a result, the browser keeps throwing net::ERR_CONTENT_LENGTH_MISMATCH when I don’t get the right content-length. I’ve tried several strategies, all of which have failed :

  • Computing the size manually (Seconds * bitrate(kbps) * (1024 / 8)).
    This produces an approximate answer, since I only know the length down to the nearest couple of seconds. Even though I’m relatively close, I still end up getting the same MISMATCH error.

  • Piping the Stream to a buffer, getting the buffer’s length, and piping the buffer to the browser
    This works, but it can take 15-20 seconds to load each song. It’s incredibly slow and puts a considerably larger load on the server