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• How to transcode a video to custom resolution using Xamarin.MP4Transcoder.Transcoder

  12 mai 2017, par Prashant

  I need to transcode a video to 640*480 resolution using Xamarin.MP4Transcoder.Transcoder. Currently there are 2 available resolutions 720pFormat and 960x540Format. There is a method called Transcoder For (IMediaFormatStrategy strategy) available in Transcoder class.

  I can create MediaFormat object with MIME Type, Width and Height
  by below mentioned code snippet :

  MediaFormat obj = MediaFormat.CreateVideoFormat("video/mp4", 480, 640);


  but the problem is how can assign it to IMediaFormatStrategy or is there any other way to achieve this.

  Piece of code for Transcoding a video:
  
  
  
  Xamarin.MP4Transcoder.Transcoder.For960x540Format().ConvertAsync(inputFile, outputFile, f =>
                                {
                                  onProgress?.Invoke((int)(f * (double)100), 100);

                                  
                                } );
  
  
  
  inputFile: Video file which needs to be transcoded.
  
  outputFile: Resultant file generated after transcoding.

  For more info you can refer https://github.com/neurospeech/xamarin-android-ffmpeg

  Any help is appreciated. Thanks in advance !!

• using ffmpeg to record highest resolution offered by Facetime cameras (mac)

  7 mai 2017, par user1361529

  I am using the following code successfully to record a video feed from my mac

  ./ffmpeg -f avfoundation -framerate 30  -i "default" out.mp4

  This however seems to be recording video at the lowest resolution of 320x200

  My camera supports the following resolutions :

  [avfoundation @ 0x7ff7b2800000] Supported modes:
  
  [avfoundation @ 0x7ff7b2800000]   1280x720@[1.000000 30.000000]fps
  
  [avfoundation @ 0x7ff7b2800000]   640x480@[1.000000 30.000000]fps
  
  [avfoundation @ 0x7ff7b2800000]   320x240@[1.000000 30.000000]fps

  I tried manually specifying the resolution using both -s and -video_size but that seems to just scale up the low res video.

  How do I get ffmpeg to pick my 1280x720 resolution ?

  thanks

• Error while trying to stream higer resolution using ffmpeg and jsmpeg

  11 avril 2017, par trojek

  I try to do a prof of concept of streaming webcam in browser using jsmpeg. It works perfect when I use code from the documentation which is as follows :

  ffmpeg \
  
      -f v4l2 \
  
          -framerate 25 -video_size 640x480 -i /dev/video0 \
  
      -f mpegts \
  
          -codec:v mpeg1video -s 640x480 -b:v 1000k -bf 0 \
  
      http://localhost:8081/supersecret

  My webcam supports resolutions, framerates and formats as in code below :

  [video4linux2,v4l2 @ 0x2655360] Compressed:       mjpeg :          Motion-JPEG : 1920x1080 1280x720 1024x768 640x480 800x600 1280x1024 320x240
  
  [video4linux2,v4l2 @ 0x2655360] Raw       :     yuyv422 :           YUYV 4:2:2 : 1920x1080 1280x720 1024x768 640x480 800x600 1280x1024 320x240

  While I change in above code the resolution from 640x480 to e.g. 1024x768, I get an error :

  [mpeg1video @ 0x110f4e0] MPEG1/2 does not support 10/1 fps
  
  Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  I assume that camera driver change number of fps and MPEG1/2 doesn’t support that numer of fps.
  Probably I get from camera raw data (yuyv422) and it can’t play it with higer framerate when e.f. 10 for 1024x768.
  How Can I modify ffmped execution code in order to stream video in Full HD resulution ?