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• Right choice to play audio and video content

  22 juin 2012, par deimus

  What I'm doing :

  I need to play audio and video files that are not supported by Apple on iPhone/iPad for example mkv/mka files which my contain several audio channels.

  I'm using libffmpeg to find audio and video streams in media file.
  Video is being decoded with avcodec_decode_video2 and audio with avcodec_decode_audio3
  the return values are following for each function are following

  • avcodec_decode_video2 - returns AVFrame structure which encapsulates information about the video video frame from the pakcage, specifically is has data field which is a pointer to the picture/channel planes.
  • avcodec_decode_audio3 - returns samples of type int16_t * which I guess is the raw audio data

  So basically I've done all this and successfully decoding the media content.

  What I have to do :
  I've to play the audio and video accordingly using Apples services. The playback I need to perform should support mixing of audio channels while playing video, i.e. let say mkv file contains two audio channel and a video channel. So I would like to know which service will be the appropriate choice for me ? My research showed that AudioQueue service might be useful audio playback, and probably AVFoundation for video.

  Please help to find the right technology for my case i.e. video playeback + audio playback with possible audio channel mixing.

• Create video with size based on image and place a video somewhere with an offset

  10 mars 2024, par NoKey

  I am trying out FFMPEG and I am unsure how hard it is to do what I want. I have some device frames and I want to play a video inside the frame. For example, this is a device frame :

  


  

  


  Now I want to play a video within the screen of the iPhone. I already got the exact X and Y offset where the video must be placed to show it correctly. I have the following challenges to make it work, and I want to make sure FFMPEG can do it before I spend to much time reinventing the wheel :

  


  


  • The output of the video must be as big as the PNG. This is already a
confusing part for me. I have the width and height already available,
but the things I saw is that FFMPEG will take over the input of the
video as final size. The final output of the video should of course
be the length of the input video.

    


  


  • The background must be transparant (so no black background, I want to
play the video on top of a website so it's nice if it's transparant and the corners are not black).

    


  


  • The ability to place a video somewhere with a specified X and Y
offset inside the device frame.

    


  


  • Not sure if it's possible in the same command, but maybe the video
needs to be resized to make it fit. I got the exact dimensions for
the video.

    


  


  


  The things I struggle most is point 1 where the output video must have a transparant background and where the device frame is placed in. Does anybody got tips ?

  


• iOS switching between audio & subtitle tracks added using ffmpeg

  27 décembre 2019, par Tony M

  Edit : Title altered to reflect that the answer and comments by @llogan cover switching between both audio and subtitle tracks.

  I have an m.mp4 with English audio and want to add a second audio stream in Italian so that I can play either language using the iPhone. When I used this command :

  ffmpeg -i m.mp4 -i ita.mp3 -c copy -map 0 -map 1 out.mp4 

  the output from ffmpeg -i out.mp4 (see below) shows that a new audio stream is added, and I can switch between audio streams using the VLC player. Yet when I transfer the video to the TV app and play it on either MacOS or iOS it only plays the original English and I see no options to play other languages.

  How do I get it to be able to switch between either audio on iOS ?

  Here is the output from ffmpeg -i out.mp4:

      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 400x300 [SAR 1:1 DAR 4:3], q=2-31, 482 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 24k tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 102 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
      Stream #0:2: Audio: mp3 (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 152 kb/s
  
      Metadata:
  
        encoder         : LAME3.100
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #0:1 -> #0:1 (copy)
  
    Stream #1:0 -> #0:2 (copy)