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• Why does Youtube player stretch MPEG1/2 video not H.264 ?

  25 juin 2017, par Maru

  I want to upload the video on Youtube and I have this particular MKV file.

  

  and I used ffmpeg to convert it to MP4 and hard code the ass subtitle into it.

  Now my question is

  When I simply tried converting the video without a sub and uploaded on Youtube,
  so it retained its original vcodec.

  ffmpeg -i "input.mkv" -c:v copy -c:a aac "output.mp4"

  The video (vcodec MPEG-1/2) is played with 16:9 ratio.

  However, when I put a sub on it, so the video need to be re-encoded.
  (In this case, I chose to preserve the quality by making it lossless.)

  ffmpeg -i "input.mkv" -preset veryslow -crf 0 -c:a aac -vf "ass=sub.ass" "output.mp4"

  Now the subbed video has vcodec of H.264.

  However, Youtube player keep its original aspect of 720x480 and there is a black bar on the side of the video.

  Therefore, I am curious why is it such a case ? even though VLC told me that both has the same resolution of 720x480.

  Furthermore, is there anyway I can adjust the aspect ratio on Youtube ?

  I know that I can simply scale the video with ffmpeg,

  but I was wondering if there is anyway I can tell Youtube to play the aspect ration that I want ? I think the formatting tags no longer works....

• vf_showinfo : minimum widths for some early fields

  15 janvier 2015, par Peter Cordes

  vf_showinfo : minimum widths for some early fields
  Depending on FPS, the pts_time string often changes length :
  
  ... pts_time:36.1 ...
  
  ... pts_time:36.1333 ...
  
  etc.
   The length changes make the output bounce around horribly, making it
  
  hard to scan down a column farther right than pts_time.
  The solution is to set minimum widths for n, pts, pts_time, and pos.
  
  This patch doesn’t touch any of the fields in mean / stddev.
   The widths aren’t intended to be wide enough that they’re never
  
  exceeded, but you’ll see only an occasional ripple to a new alignment,
  
  rather than bouncing.  (Some fields, like pos, increase monotonically,
  
  which is why I left the minimum width for the field be smaller than it
  
  often gets to.)
  Signed-off-by : Peter Cordes <peter@cordes.ca>
  

  • [DH] libavfilter/vf_showinfo.c

• fftools/ffmpeg_enc : stop configuring filter inputs from encoder flush

  30 avril 2023, par Anton Khirnov

  fftools/ffmpeg_enc : stop configuring filter inputs from encoder flush
  When no frames are ever seen by an encoder, encoder flush will do a
  
  last-ditch attempt to configure its source filtergraph in order to at
  
  least get the stream parameters. This involves extracting demuxer
  
  parameters from filtergraph source inputs, which is
  
  * a bad layering violation
  
  * probably unreachable, because decoders are flushed before encoders,
  
    which should call ifilter_send_eof(), which will also set these
  
    parameters ; however due to complex control flow it is hard to be
  
    entirely sure this code can never be triggered
  Even if this code can actually be reached, it is probably better to
  
  return an error as the comment above it says.
  

  • [DH] fftools/ffmpeg_enc.c