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• FPS reduction for H264 [closed]

  11 mai 2024, par Александр А

  There is a USB camera that sends H264 frames with a frequency of 30 fps in a resolution of 1920x1080, GOP size 30 or 60 (1 or 2 I frame per second depending on the camera), which requires throughput of about 6 mbit/s. It is necessary to reduce this to no more than 2 mbit/s. All this is done on a weak ARMv7, so the option of transcoding is extremely resource intensive, especially considering that I did not find how to do it as a GPU Mali.

  


  Given that the basic functionality is performed on the framework ffmpeg, is it possible to reduce the frame rate, ideally to 10 fps, WITHOUT loss of quality and decoding ?

  


• Inconsistant rendering in libmelt XML and C interface and 'hold' producer and avformat consumer

  14 octobre 2016, par Leif Andersen

  I am trying to create a short video that is just a single image. (I know its a bit silly, but its a test for something bigger).

  The code I have for rendering it is :

  #include <framework></framework>mlt.h>
  
  #include 
  
  #include 
  
  
  
  int main() {
  
    if(mlt_factory_init(NULL)) {
  
      mlt_profile p = mlt_profile_init(NULL);
  
      mlt_consumer target = mlt_factory_consumer(p, "avformat", 
  
      mlt_producer source = mlt_factory_producer(p, "hold", "/Users/leif/logo.png");
  
      mlt_producer_set_in_and_out(source, 0, 10);
  
      mlt_consumer_connect(target, mlt_producer_service(source));
  
      mlt_consumer_start(target);
  
  
  
      sleep(5);
  
      mlt_consumer_stop(target);
  
  
  
      mlt_consumer_close(target);
  
      mlt_producer_close(source);
  
      mlt_factory_close();
  
    } else {
  
      printf("No\n");
  
    }
  
  
  
    return 0;
  
  }

  Where logo.png is this file.

  When I run this code and play output.mp4, the picture comes out all garbelled. There is a green line in the middle and the logo is superimposed on itself a lot.

  On the other hand, if I change the consumer to be SDL, the image plays just fine.

  And finally, if I change the consumer to be XML, and then use the melt command line application to render it :

  melt -consumer avformat:xmlout.mp4 output.xml

  and play the video, it also plays fine.

  Is there something I am missing in the avformat consumer that I should be setting ? Or something else that I am missing here ?

  Edit : For reference, the outputted xml file : output.xml is :

  <?xml version="1.0" encoding="utf-8"?>
  
  <mlt version="6.2.0" root="/Users/leif/src/video/private" title="Anonymous Submission" parent="producer0" in="0" out="10">
  
        <profile description="DV/DVD PAL" width="720" height="576" progressive="0" colorspace="601"></profile>
  
    <producer title="Anonymous Submission" in="0" out="10">
  
      <property>15000</property>
  
      <property>pause</property>
  
      <property>/Users/leif/logo.png</property>
  
      <property>1.06667</property>
  
      <property>0</property>
  
      <property>onefield</property>
  
      <property>hold</property>
  
      <property>1</property>
  
    </producer>
  
  </mlt>

• Trying to upload a video to a server and then play it back to a video view (Xamarin android)

  31 juillet 2016, par stackOverNo

  I’m currently working on a xamarin.android project, and am attempting to upload a video to an aws server, and then also be able to play it back. The upload is working correctly as far as I can tell.

  I’m retrieving the file from the user’s phone, turning it into a byte array, and uploading that. This is the code to upload :

  if (isImageAttached || isVideoAttached)
  
              {
  
                  //upload the file 
  
                  byte[] fileInfo = System.IO.File.ReadAllBytes(filePath);
  
                  Task<media> task = client.SaveMediaAsync(fileInfo, nameOfFile);
  
                  mediaObj = await task;
  
  
  
                  //other code below is irrelevant to example
  
              }
  
  </media>

  and SaveMediaAsync is a function I wrote in a PCL :

  public async Task<media> SaveMediaAsync(byte[] fileInfo, string fName)
  
      {        
  
          Media a = new Media();
  
          var uri = new Uri(RestUrl);
  
  
  
          try
  
          {
  
  
  
              MultipartFormDataContent form = new MultipartFormDataContent();
  
              form.Add(new StreamContent(new MemoryStream(fileInfo)), "file", fName);  //add file
  
  
  
              var response = await client.PostAsync(uri, form);            //post the form   client is an httpclient object
  
              string info = await response.Content.ReadAsStringAsync();
  
  
  
      //save info to media object
  
              string[] parts = info.Split('\"');
  
              a.Name = parts[3];
  
              a.Path = parts[7];
  
              a.Size = Int32.Parse(parts[10]);
  
  
  
          }
  
          catch(Exception ex)
  
          {
  
      //handle exception
  
          }
  
  
  
          return a;
  
  
  
      }
  
  </media>

  After uploading the video like that, I’m able to view it in a browser using the public url. The quality is the same, and there is no issue with lag or load time. However when I try to play back the video using the same public url on my app on an android device, it takes an unbelievably long time to load the video. Even once it is loaded, it plays less than a second of it, and then seems to start loading the video again(the part of the progress bar that shows how much of the video has loaded jumps back to the current position and starts loading again).

   VideoView myVideo = FindViewById<videoview>(Resource.Id.TestVideo);
  
  
  
   myVideo.SetVideoURI(Android.Net.Uri.Parse(url));
  
  
  
   //add media controller
  
   MediaController cont = new MediaController(this);
  
   cont.SetAnchorView(myVideo);
  
   myVideo.SetMediaController(cont);
  
  
  
   //start video
  
   myVideo.Start();
  
  </videoview>

  Now I’m trying to play a 15 second video that is 5.9mb. When I try to play a 5 second video that’s 375kb it plays with no issue. This leads me to believe I need to make the video file smaller before playing it back, but I’m not sure how to do that. I’m trying to allow the user to upload their own videos, so I’ll have all different file formats and sizes.

  I’ve seen some people suggesting ffmpeg for a c# library to alter video files, but I’m not quite sure what it is I need to do to the video file. Can anyone fill in the gaps in my knowledge here ?

  Thanks for your time, it’s greatly appreciated !