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• SDL_SetVideoMode fails under Android ?

  17 avril 2013, par user1568549

  I am trying to buid a Video Player for android using libsdl for rendering and libav for decoding.

  First, i cross-compiled the sdl library for Android platform.
  Then i ceated the jni layer for my sdl cpp file(already tested under ubuntu)
  but when i test it under Android it fails(with fatal error segv11 signal) exactly at the beginning in the following instruction :

   this->screen = SDL_SetVideoMode(width, height, 0, 0);

  Does anyone know any workaround for this error ?

  Does anyone know how to display video using sdl under android ?
  And is there any instructions or steps that i must follow in order to render SDL gui under android ?

  Thanks in advance !

• 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 ?

• Android ffmpeg save and append h264 streamed videos

  8 octobre 2012, par Stefan Alexandru

  I need to save a video file generated by two video streams coming from two different sources. I'm using rtsp over tcp/ip, and the videos are encoded with h264.
  I need to first record the video from the first source and than continue with the second source.
  So what I tried was to declare two AVFormatContext instances, initialize both with avformat_open_input(&context, "rtsp://......",NULL,&options)
  and then read frames with av_read_frame(context,&packet)
  and write them in the video file av_write_frame(oc,&packet);
  It works fine saving the video from the first source, but if by example I saved y frames from the first context, when I try reading and saving the frames from the second context in the same file, for the first y frames I am tring to save, av_write_frame(oc,&packet2);
  would retun -22, and would not add the frame to the file.

  I think the problem is that the context variable remembers how many frames were read, and it gives every read packet an identification number, to make sure it isn't written twice. But when I'm using a new context those identification numbers reset, the AVOutputFormat or the AVFormatContext also retain the id of the package they are expecting to receive, and would not write anything until they receive a package with that id.
  Now I'm wondering how could I solve this inconvenience. I can't find any setter for that id, or any way to reuse the same context. I thought to modify the ffmpeg sources but they are pretty complex and I couldn't find what I was looking for.
  An alternative would be to save the two video in two different files but, I don't know how to append them afterwards, as ffmpeg can only append videos encoded with mpeg and rencoding the video isn't really an option, as it will take to much time. Also I couldn't find any other functional way to append two mp4 videos encoded with h264.

  I'll be happy to hear any kind of usable ideea to this problem.