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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 !!

• 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 ?

• FFmpeg- Concat videos with unknown resolution/frame size/rate etc

  21 mars 2017, par Karandeep Atwal

  On android platform, I am using this library for concatenating videos.
  For mp4 files with Same Properties like frame-size,resolution etc. I have succeeded concatenating by this command-

  -f concat -safe 0 -i inputfile.txt -codec copy Outputfile

  where inputfile.txt contains-

  file /storage/emulated/0/demo/vid1.mp4
  
  file /storage/emulated/0/demo/vid2.mp4
  
  file /storage/emulated/0/demo/vid3.mp4
  
  file /storage/emulated/0/demo/vid4.mp4

  But, this command only works if input video files have SAME Properties eg. videos made from camera app.If we add other mp4 videos to the input eg. Whatsapp Videos, then I got corrupted Output. It is described here.

  I have read about Concat-Filter ,But this is not working in my case giving me errors like Media-mismatch asked here, different SAR value,frame-size etc. doesn’t match. I also used this Command but it takes about three hours for 25Mb & 5Mb video.

  I want to choose as many random videos from storage and want to concat them. I also think of converting every chosen video to same bitrate, same frame size, same aspect ratio, but it is time-consuming.

  What would be the Best Way to Concat videos of unknown type using ffmpeg commands ?