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• Transfoming images and mp3 files into a video file on android

  4 février 2014, par Alin

  I am thinking to start the development of a new project and I have some ideas in mind, but I am not sure how much is doable in android.
  The steps of the app would be :

  1. The user selects a set of images from Gallery
  2. The user selects an audio file from external storage
  3. I combine the images and the sound (each image is displayed for a timeframe) into a movie file that can be exported to YouTube

  From my research I wasn't able to find any way to create the movie. All the answers contained links to android NDK and external codecs.

  So my question is : which would be the easiest way of making this on android ?

• Re-stream (forward) UDP-Live-Video-Stream (using winsock) reduce video quality ?

  18 août 2014, par vantrung -cuncon

  So, I used ffmpeg to stream the live webcam using UDP protocol to port 1111 :

  ffmpeg -f dshow -i video="Lenovo EasyCamera" -f mpegts udp://localhost:1111

  When I played it directly by ffplay from port 1111, everything worked properly :

  ffplay udp://localhost:1111

  I got the video quality like this :

  

  So I think, I could write some winsock-codes to listen to port 1111 & forward any UDP packet that it catches to port 2222. Thus, I could simulate that I’m streaming to port 2222. My code is something like this :

  ' // Please note that this is the simplified code - cause it worked
  
  ' // i've just post the key lines
  
  Winsock1.Bind 1111
  
  Winsock2.remotePort = 2222
  
  
  
  WinSock1.GetData myPacket
  
  Winsock2.SendData myPacket

  Then I tried playing the stream from port 2222 using ffplay :

  ffplay udp://localhost:2222

  Well, I don’t know why the video quality turned to this bad :

  

  The point is that, I’ve sent the same UDP packets in the same order as the streaming-source. What could be wrong here ?

  ---

  PS : I’ve tried a similar experiment like above with TCP, but the end-result video quality was as good as direct streaming. So, could this be a problem of UDP ?

  ---

  PS2 : I’ve tested the UDP packet loss & disorder by replacing the ffplay with a socket that listen to port 2222 & print out all the received packets. But the result is all 10,000+ packets were in correct order & nothing lost. What a crazy phenomenon ?

• Why does -filter:v fps=60 need re-encoding ?

  16 avril 2024, par kwjsksai

  I mean, let's say 30 fps -> 60 fps. You just need to duplicate frames.
  
Decode a frame and present it at 2 timepoints.
  
I know mp4 can present a frame at different timepoints, right ?
  
So why is re-encoding needed ? with h264 codec and heavy computing...
  
I thought it could be just some metadata work.

  


  ffmpeg -i 30fps.mp4 -filter:v fps=60 out.mp4