Recherche avancée

Sur d’autres sites (6881)

• video processing on android using ndk with ffmpeg and opencv is very slow

  26 novembre 2014, par Zhiqiang Li

  I’m doing some video processing on android using ndk.

  What I’m doing now is decode the video using ffmpeg, grab the frame, convert it to opencv mat, then overlay some images on it, then convert it back to avframe, encode it back to a video.

  But it’s very slow ! It takes about 50 seconds to process a 480*480 video with 15 fps.

  I tried to do this using opengl es, reading the result image using glReadPixels, but from what I understand, glReadPixels doesn’t really work on some devices. So I had to give it up.

  As I understand, I have some very expensive operations in my current workflow,

  1. covert a AVFrame from yuv to bgr color space, then convert to opencv mat
  2. overlay a mat on another mat
  3. covert a opencv mat to AVFrame, then convert the frame from bgr to yuv space, then encode it into a video.

  So, are there ways to improve my current workflow ?

  I’m adding multithread feature, but only devices with multicore cup can benefit from that.

• How to effectively kill a frozen subprocess in Python ?

  2 janvier 2014, par Konos5

  I am dealing with a rather odd issue.

  I've written a Python wrapper (in Python 2.6.6) for a year old version of ffmpeg. The problem is that given a very particular video, ffmpeg stops working normally (clunky output, full cpu usage, no end stage etc) and takes the python interpreter down with it.

  Now, if I run ffmpeg with my encoding options directly from a terminal and the problematic video as input, ffmpeg won't immediately respond to Ctrl-c. I'll have to wait for a hefty of 10 seconds or more before it exits and gives me back the prompt. However if I use a 'healthy' video instead, it will simply print Received signal 2: terminating. and gracefully exit.

  In the python wrapper I use p.kill() to no effect. The behavior is exactly the same a.k.a I have to wait 10 sec before the program exits. How can I immediately stop ffmpeg when it freezes with some problematic video ?

  Note that if I do a double Ctrl-c I get the prompt back immediately no matter what.

• How do I convert flac to wav on iOS ?

  8 juin 2017, par popctrl

  I have a file which is encoded with FLAC and I want to convert it to WAV.

  I have added this FFMpeg lib to my project and imported it.

  I see some code from this answer, but I am unclear on how to use it :

  #import "avformat.h"
  
  
  
  // Some code goes here
  
  
  
  /*
  
   *   avformat_open_input(AVFormatContext **ps, const char *filename, AVInputFormat *fmt, AVDictionary **options)
  
   */
  
  int openInputValue = avformat_open_input(&pFormatCtx, utf8FilePath, inputFormat, nil);
  
  NSLog(@"%s - %d # openInputValue = %d", __PRETTY_FUNCTION__, __LINE__, openInputValue);

  I currently have this code in a function which takes NSData holding the FLAC file. If avformat_open_input is the correct call, how do I set the variable ? If it is not the correct call, what is ?

  This question seems like a duplicate but it doesn’t really have a good answer.

  Also note that I don’t want a player. This file contains MQA so I need to run it through my own custom decoder.