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• Android video color ajustments

  4 octobre 2012, par Christian

  I'm working on an Android app that among other things will allow the users to make short videos, apply funny effects to them and share them with one another. To begin with, i'm looking for simple color-effects like grayscale, brightness, contrast, sepiatoning, and such.

  All this would be very simple by using the camera-class which can apply the color effects at recording-time - at least most phone's cameras can - i've tested some using Camera.getParameters().getSupportedColorEffects();. But the thing is : i need to do it after the recording has been done : the user would open a video, and choose among a set of effects to apply ; then upload that changed video to a shared server.

  I can't for the love of * find a good way to do this.

  Android doesn't seem to include any videoutilities in the sdk. The android.media.effect package can do some effects, but only backdropper for videos, the rest are for images. Extracting bitmaps from the surfaceview of a videoview during playback doesn't work, it just returns an all-black bitmap. It seems like there's no way to intercept the datastream between the storage and the screen. and apply the effects there. I've started to look into using the FFmpeg library to decode a video file so i can get access to the data, but that requires quite a bit of native coding, and also requires separate compiles for various CPU architectures, so it's very messy. I thought that as the camera can apply these effects (on a Sony LT26i : none, mono, negative, solarize, sepia, posterize), perhaps one could feed the recorder with a videostream not from the camera, but from the memory, and by that way use a stored video file ?

  Do anyone know if there is a good way to apply effects to a video - after it has been recorded ?

• Mix Audio tracks with offset in SOX

  4 août 2012, par Laramie

  From ASP.Net, I am using FFMPEG to convert flv files on a Flash Media Server to wavs that I need to mix into a single MP3 file. I originally attempted this entirely with FFMPEG but eventually gave up on the mixing step because I don't believe it it possible to combine audio only tracks into a single result file. I would love to be wrong.

  I am now using FFMPEG to access the FLV files and extract the audio track to wav so that SOX can mix them. The problem is that I must offset one of the audio tracks by a few seconds so that they are synchronized. Each file is one half of a conversation between a student and a teacher. For example teacher.wav might need to begin 3.3 seconds after student.wav. I can only figure out how to mix the files with SOX where both tracks begin at the same time.

  My best attempt at this point is :

  ffmpeg -y -i rtmp://server/appName/instance/student.flv -ac 1 student.wav 
  
  ffmpeg -y -i rtmp://server/appName/instance/teacher.flv -ac 1 teacher.wav 
  
  
  
  sox -m student.wav teacher.wav combined.mp3 splice 3.3

  These tools (FFMEG/SoX) were chosen based on my best research, but are not required. Any working solution would allow an ASP.Net service to input the two FMS flvs and create a combined MP3 using open-source or free tools.

  EDIT :
  I was able to offset the files using the delay switch in SOX.

  sox -M student.wav teacher.wav combined.mp3 delay 2.8

  I'm leaving the question open in case someone has a better approach than the combined FFMPEG/SOX solution.

• How to wrap a C library parameter ?(Creating x264 .Net wrapper)

  6 décembre 2016, par Rella

  so in dll we have x264_param_t structure\object and a function for its setting up x264_param_apply_profile. in C we use such code to set it up

  x264_param_t param;
  
  x264_param_default_preset(&param, "veryfast", "zerolatency");
  
  param.i_threads = 1;
  
  param.i_width = width;
  
  param.i_height = height;
  
  param.i_fps_num = fps;
  
  param.i_fps_den = 1;
  
  // Intra refres:
  
  param.i_keyint_max = fps;
  
  param.b_intra_refresh = 1;
  
  //Rate control:
  
  param.rc.i_rc_method = X264_RC_CRF;
  
  param.rc.f_rf_constant = 25;
  
  param.rc.f_rf_constant_max = 35;
  
  //For streaming:
  
  param.b_repeat_headers = 1;
  
  param.b_annexb = 1;
  
  x264_param_apply_profile(&param, "baseline");

  I want to create wrapper for such.. thing. so I have libx264.dll and visual studio 2010 pro.

  How can I create .Net C# wrapper for it ?

  I am a beginner in P\Invoke stuff so I do not get a lot of it...

  what I want to achive is is frame by frame level of working with x264... By now I need only encoding parts... And all needed sample code for doing it in C is in How does one encode a series of images into H264 using the x264 C API ? . So I need to write a wrapper only for stuff mentioned there... So I am asking - how to create a wrapper on Parameter and on Function that sets up thap param. And I would love to see how to call that wrapper back from c#. So if you could provide any code in support I’d be glad to see it.