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• Cannot get transparent background with ffmpeg (HEVC to VP8/VP9)

  3 avril 2020, par Alexander BC

  I want to convert a mp4 video to any other format that supports video-transparency. I've done it in the past but I cannot get it to work again.

  



  I've followed the same guides as before :

  



  

  • Convert mp4 to webm with transparency ?

  


  • Convert mov with Alpha to VP9 Webm with Alpha Using ffmpeg

  


  • Error "Transparency encoding with auto_alt_ref does not work" when converting a .mov with Alpha to .webm with alpha with ffmpeg

  


  



  The input video is a HEVC (h265), and the background I want to remove is full white. I'm using the following command to make the conversion :

  



  ffmpeg -i input.mp4 -c:v libvpx -b:v 4M -vf "colorkey=0xffffff:0.1:0.0,format=yuva420p" -auto-alt-ref 0 transparent.webm


  



  I've also tried with VP9 (libvpx-vp9) with same result. The conversion of a single frame from a PNG source (screen captured frame) works ok.

  



  Any idea about where I could be failing in ?

  



  I hope there's nothing missing, thanks in advance.

  



  PS I'm getting a warning at the transcode process, I don't think is anything important but here it's in case is something relevant : [swscaler @ 000001e3b0dc7a40] No accelerated colorspace conversion found from yuv420p to argb.

  


• Problems with point to point streaming using FFmpeg

  16 février 2015, par UserOfStackoverflow

  I want to live stream video from webcam and sound from microphone from one computer to another but there is some problems.

  When I use this command line :

  ffmpeg.exe -f dshow -rtbufsize 500M -i video="Camera":audio="Microphone" -c:v mpeg4 -c:a mp2 -f mpegts udp://127.0.0.1:1234

  FFmpeg console starts filling with yellow color messages and stream becomes unstable : http://s16.postimg.org/qglcgr345/Untitled.png

  To solve this problem I have added new parameter to the command line to set the frame rate -r 25 :

  ffmpeg.exe -f dshow -rtbufsize 500M -r 25 -i video="Camera":audio="Microphone" -c:v mpeg4 -c:a mp2 -f mpegts udp://127.0.0.1:1234

  After I added -r 25 problem with yellow color messages disappears but then appears another problem. When I fresh start FFmpeg with this command line video and sound looks synchronous but after one or two minutes appears 25 seconds lag between video and sound, sound goes behind video. I have tried that with different protocols UDP, TCP, RTP but problems are the same. Please help me !

• How to link and call function of prebuild static native library from android studio

  23 janvier 2017, par Janaki

  I need to change pitch and time stretching of an audio. For this I am using prebuild static library. Currently I am having libZtxAndroid.a static library and corresponding header file which contains function declaration. But I don’t know how to load this library in my android studio app and call native function from java code. I explored many links and tried to load this library. But all attempts are failed. This is the one link which I have tried last time https://tariqzubairy.wordpress.com/2012/03/12/use-of-prebuild-static-library-compiled-with-android-toolchain/

  Also I am using FFMPEG shared library and MP4Parser (https://github.com/sannies/mp4parser) library in this app for adding water mark to video and merging audio respectively. Can any one help from basics.

  1. How to load static library ?
  2. Where I need to place that static library ?
  3. Where I need to create jni folder (folder structure) ?
  4. How to call function available in that static library with the help of header file from java code ?