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• Scaling videos for device that doesn't support aspect ratio metadata

  18 juillet 2017, par forthrin

  I have hundreds of videos which are all approximately 4:3 format, but with different resolutions and various cropping (eg. videos may be 640x480, 640x470, 630x480, etc.).

  I converted the videos into a fixed screen size (160x128) for a primitive device. When playing the videos on the device, some appear "thin", while in VLC on my computer, the aspect ratio is correct.

  I assume the reason for this is that the video player on the primitive device doesn’t honour the aspect ratio metadata in the video file. Here are two examples of metadata :

  • 320x240 SAR=1:1 DAR=4:3 (Displays correctly on device and desktop)
  • 480x480 SAR=4:3 DAR=4:3 (Displays thin on device, correct on desktop)

  How can I create a general command line that will give all videos correct playback on my primitive device, regardless of their original size and aspect ratio ?

  The best would be to somehow ask ffmpeg to remove the metadata, and compensate for it when scaling. Another possible option would be to add black bars so the video is always 160x128 pixels.

  I’m open to any solution. Below is my current version :

  for f in *; do ffmpeg -i $f -vcodec mpeg4 -vf scale=160:-1 out/$f; done

• FFmpeg Dropping Aspect Ratio on FLV Output

  16 septembre 2017, par Mike B

  I am having an issue with FFmpeg dropping the aspect ratio when converting a 1920x1080 stream to a lower resolution (please see below for more information). The objective is to take the output from TVHeadend and convert it to a FLV format that I can stream outside of my house.

  ffmpeg -c:v mpeg2_mmal -i http://192.168.1.142:9981/stream/channelnumber/10.1?profile=pass -c:a libfdk_aac -profile:a aac_he_v2 -b:a 32k -ac 2 -async 48000 -c:v h264_omx -b:v 1800k -sws_flags fast_bilinear -vf scale=720:540 -keyint_min 0 -g 100 -f flv rtmp://192.168.1.110:1935/live/test

  This produces the following onscreen output :

  Output #0, flv, to 'rtmp://192.168.1.110:1935/live/test':
  
    Metadata:
  
      encoder         : Lavf57.82.100
  
      Stream #0:0: Video: h264 (h264_omx) ([7][0][0][0] / 0x0007), yuv420p, 720x540 [SAR 4:3 DAR 16:9], q=2-31, 1800 kb/s, 29.97 fps, 1k tbn, 29.97 tbc
  
      Metadata:
  
        encoder         : Lavc57.105.100 h264_omx
  
      Stream #0:1(eng): Audio: aac (libfdk_aac) (HE-AACv2) ([10][0][0][0] / 0x000A), 48000 Hz, stereo, s16, 32 kb/s
  
      Metadata:
  
        encoder         : Lavc57.105.100 libfdk_aac

  Based on the onscreen output, it appears that that SAR and DAR are correct. It is only when you examine the actual files that the aspect ratio has been dropped.

  Input #0, hls,applehttp, from 'http://192.168.1.110:8080/live/test/index.m3u8':
  
    Duration: N/A, start: 109.116000, bitrate: N/A
  
    Program 0 
  
      Metadata:
  
        variant_bitrate : 0
  
      Stream #0:0: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 720x540, 29.97 tbr, 90k tbn, 180k tbc
  
      Metadata:
  
        variant_bitrate : 0
  
      Stream #0:1: Audio: aac (HE-AACv2) ([15][0][0][0] / 0x000F), 48000 Hz, stereo, fltp
  
      Metadata:
  
        variant_bitrate : 0

  I modified the command to instead save to a local MP4 file :

  ffmpeg -c:v mpeg2_mmal -i http://192.168.1.142:9981/stream/channelnumber/10.1?profile=pass -c:a libfdk_aac -profile:a aac_he_v2 -b:a 32k -ac 2 -async 48000 -c:v h264_omx -b:v 1800k -sws_flags fast_bilinear -vf scale=720:540 -keyint_min 0 -g 100 ~/test.mp4

  And the issue is resolved. I have also tried adding the video filters setsar and setdar to no avail.

  I am performing this on a Raspberry Pi 3, which lacks the ability to de-interlace in hardware. To remedy this, I am simply scaling the video vertically by 1/2. I have tried scaling the output to 960x540 but the Pi has issues keeping up.

• how to resize and keep video keep aspect ratio and pad with black bars [duplicate]

  20 septembre 2017, par Sepehr Norouzi

  This question already has an answer here :

  • Use ffmpeg to generate video thumbnail without any distortion
    
    2 answers
    
  • FFMPEG (libx264) “height not divisible by 2”
    
    4 answers
    

  I need to resize my video with ffmpeg.

  It’s MP4 with width 640 and height 360. How can i resize it and keep aspect ratio and pad with black bars so that the video size is exactly ... ?

  I already tried some codes on Linux but it just damages file.