Recherche avancée

Sur d’autres sites (6457)

• Using ffmpeg, the function av_find_input_format("avfoundation") return null

  28 avril 2019, par guojing

  I run this code in iPad mini 4 (Model A1538), iOS 11.2.6

  Try to record audio by FFmpeg.

  av_register_all();
  
  avcodec_register_all();
  
  avdevice_register_all();
  
  
  
  AVFormatContext *pFormatCtx = avformat_alloc_context();
  
  AVDictionary* options = NULL;
  
  av_dict_set(&options,"list_devices","true",0);
  
  AVInputFormat *iformat = av_find_input_format("avfoundation");
  
  printf("==AVFoundation Device Info===\n");
  
  avformat_open_input(&pFormatCtx,"",iformat,&options);
  
  printf("=============================\n");
  
  
  
  if(avformat_open_input(&pFormatCtx,"0",iformat,NULL)!=0){
  
      printf("Couldn't open input stream.\n");
  
      return;
  
  }

  pFormatCtx = NULL, and iformat = NULL.

  Why should this happen, did I missed anything to set ?

• Apply sound effects on a video file

  31 mars 2013, par talhamalik22

  I am a little miss guided here and it seems i am totally lost. I am developing an android app and its core idea is to develop a video recorder and video player that applies some sound effects on the voice of the people or any sound that it records. Sound effect means that if i make a video of a person who is giving some speech then there should be no effect on video but his/her voice should appear like voice in talking tom cat app. I hope you understand the idea. Similar app is Helium Booth you can check it here. I am trying to use libraries like libSonic, libpd and tried to use XUGGLE too.
  Read somewhere that Xuggle is not really developed for mobile devices so left it. Now what i want is that it should apply this effect on voice on the run time i.e while recording the pitch of the sound should be alterd and saved immediately. And what i am getting with these libraries is that i can apply sound effect after video is recorded. So it means i need to rip the audio from the video and then apply the change in pitch and frequency and again concatenate this audio file with the old video file. And i have no idea how to do it.
  Please show me the right approach and tools if possible.

  Regards

• Can ffmpeg trim the beginning of a video as it's written ?

  3 janvier 2024, par ttshaw1

  I'm working on an Android app where I want to keep a 30s buffer of video, and at arbitrary times save it. I have a few requirements :

  


  

  • I want to make sure I don't miss or duplicate any frames. So I think periodically starting and stopping recording won't work

  


  • I found that simultaneously encoding two video streams puts my CPU under a lot of strain, so I want to avoid doing that

  


  • I don't want to store a ring buffer of 30s worth of frames in memory as that'll require too much memory. So I think I need to encode them to a video file on disk as they come in. (though I'm realizing maybe I could write the frames to disk and encode them when I have a 30s buffer I want to keep)

  


  


  This all leads me to think the best solution would be something like a typical camera app where a video is written to an mp4 file as it's recorded. But to keep the filesize reasonable, I'd like to have the output file continuously trimmed to the last 30s, plus or minus a keyframe interval.

  


  I know that ffmpeg can do that for a video that's not being currently written. But I don't know if something about the format of an mp4 would prevent doing that for a video that is being written. For example, if an mp4 was essentially a series of bitmaps with timestamps, I'd think it's easy for ffmpeg to chop off some number of frames at the beginning while the camera API is writing frames to the end. Is there anything about the mp4 format that makes it too complicated to do that in practice ? Or is this a question that depends on the camera API's implementation ?