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• Is variable resolution possible in MPEG-4 or Matroska ?

  29 août 2020, par Chris_F

  It's become increasingly common for movies to contain sections with varying aspect ratios. For instance, the movie The Dark Knight is is sometime 16:9 full frame, and at other times 2.40:1 with letter boxing. This is fine when viewed on a 16:9 (or even 4:3) screen, but if you try to watch it on a 2.40:1 screen you will get simultaneous horizontal and vertical letterboxes. Extremely undesirable.

  


  Currently I use MPC-HC, which has a feature where it is able to analyze the video in real time, detect letter boxing, and dynamically crop the video. This works pretty well, but it's kind of an ugly solution. Are there any video formats that allow meta data like image resolution to change throughout the video ?

  


• Have ffplay output current time in millisecond resolution

  21 août 2020, par 12.yakir

  What are the arguments for ffplay to output the duration/time-stamp of the current frame in millisecond resolution (dumping it to stderr or stdout, not embedding or overlaying it into the video) ?

  


  Right now playing a video (and pausing it) will look like this :

  


  ~$ ffplay -i video.mp4 -hide_banner -loglevel 8 -stats
   2.09 A-V: -0.004 fd=   6 aq=   31KB vq=   84KB sq=    0B f=0/0


  


  Note that the current time, 2.09, is in "centi-seconds" (one hundredth of a second), not millisecond (one thousandeth of a second).

  


  Ideally, it would output only the current time in millisecond resolution :

  


  ~$ ffplay -i video.mp4 -hide_banner -loglevel 8 -stats <enter magic="magic" arguments="arguments" here="here">&#xA;   2.093&#xA;</enter>

  


• FFMPEG : Convert WebM VP8/VP9 multi-resolution video to MP4 (H.264)

  28 janvier 2022, par thedeadalive

  I have been trying to convert a multi-resolution WebM video ( VP9/VP8/H.264 ) (1280 x 1080 till the half, thereafter 1080 x 1280) to MP4 container with H.264 encoding for video.

  


  When transcoded with FFMPEG is locking into the frame size it's encountering at the start of the video (1280 x 1080 in this case) when transcoded with libvpx (for VP8 and VP9) and libx264 (for H264).

  


  The only instance i could get it right was when the Input WebM was having H.264 video and opus Audio, and ffmpeg was instructed to just copy the video stream and trans-code the Audio to aac only.

  


  Is there way in make ffmpeg support multi-resolution video transcoding ?

  


  How to generate a sample video : On a Chrome or Firefox (on a device that supports auto rotation and has different resolution on portrait and landscape) that supports mediaRecorder API goto this link : https://webrtc.github.io/samples/src/content/getusermedia/record/ , start recording a video , while recording the video, change orientation, stop recording and download the video. file)

  


  Discussion Reference : https://groups.google.com/a/webmproject.org/forum/# !topic/webm-discuss/IgumDyMAHY0