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• Resizing an mp4 with ffmpeg reduces color quality

  16 novembre 2019, par Jules

  Initially I’ve downloaded a video from an m3u8 to an mp4. The color of the downloaded video is fine at this point and mirrors the source. This is the command I’m using..

  ffmpeg -i https://...default.m3u8 -acodec copy -vcodec copy download.mp4

  My next step is to resize the source video from 1142 x 652, to create a new larger letter-box / pillar-box video of 1920 x 886

  ffmpeg -i download.mp4 -vf "scale=(iw*sar)*min(1920/(iw*sar)\,886/ih):ih*min(1920/(iw*sar)\,886/ih), 
  
    pad=1920:886:(1920-iw*min(1920/iw\,886/ih))/2:(886-ih*min(1920/iw\,886/ih))/2" resized.mp4

  However the color of the resized video is different, it could be that the amount of colours has been reduced, but that’s just a guess.

• Converting a YUV file to .mp4 using ffmpeg for a beginner

  11 mars 2014, par GreenGodot

  I'm a newbie when it comes to linux and ffmpeg but I need to use Evalvid to stream a video file. I want to stream a file for around 500 seconds. My plan is to download one of the videos from here :

  http://media.xiph.org/

  For this example I downloaded a video of Big Buck Bunny (in this case the 480p version). it came in an xz which I used unxz on, getting me a .y4m file which I used ffmpeg to convert to a YUV file.

  ffmpeg -i big_buck_bunny_480p24.y4m bbb.yuv

  My problem is right here, I try to use examples from this site but they don't work. What is the exact command to convert it to a .mp4 file using ffmpeg or are their easier alternatives to use ?

  I have tried :

   ffmpeg -f rawvideo -s:v 1920x1080 -r 25 -i bbb.yuv -c:v libx264 output.mp4

  and this starts the conversion process but after 5 minutes I get an invalid buffer value error and the output is a mess of colours.

• Convert from NV12 to RGB/YUV420P using libswscale

  29 août 2017, par Ruben Sanchez Castellano

  I’m developing an application which needs to transform NV12 frames from h264_cuvid decoder to RGB in order to modify those frames. I checked this question but I don’t not the ’Stride’ value.

  My code is the following :

  uint8_t *inData[2] = { videoFrame->data[0], videoFrame->data[0] + videoFrame->width * videoFrame->height };
  
  int inLinesize[2] = { videoFrame->width, videoFrame->width };
  
  
  
  sws_scale(convert_yuv_to_rgb, inData, inLinesize, 0, videoFrame->height, aux_frame->data, aux_frame->linesize);

  But it does not work. Although the problem is on colours because I can see the luminance plane correctly.