[FFmpeg-trac] #5123(avfilter:new): PAD filter works correctly only when vcodec is NOT H264

FFmpeg trac at avcodec.org
Wed Jan 6 13:31:04 CET 2016

#5123: PAD filter works correctly only when vcodec is NOT H264
             Reporter:  SarasotaSlim  |                     Type:  defect
               Status:  new           |                 Priority:  normal
            Component:  avfilter      |                  Version:  2.8.3
             Keywords:  pad           |               Blocked By:
             Blocking:                |  Reproduced by developer:  0
Analyzed by developer:  0             |
 Summary of the bug: PAD filter works correctly only when vcodec is NOT
 How to reproduce: Try it, with one of each
 % ffmpeg -i input ... output
 ffmpeg version
 built on ...
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.

   MyTemplate to grab 't-seconds' of a video file, starting 'ss-seconds'
 into it
         ffmpeg -i MOVIE.mkv -acodec copy -vcodec copy -t 60 -ss 240 MOVIE-

 So, I grabbed 180 secs (3 mins) of one of mine (it was ripped from a DVD
 using MakeMKV...720x480, vcodec=MPEG2) :
         ffmpeg -i  Raising_Arizona(1987).mkv -acodec copy -vcodec copy -t
 600 -ss 60 Raising_Arizona-3mins.mkv

 For this next part, you need be sure you have a FULL distrib of FFMPEG for
 Windows (that includes filters),
 so if this next step fails because it can't find filters, get full version
 (static pkg, which has filters inside) here:
         http://ffmpeg.zeranoe.com/builds/                       (Look for
 the windows build section)

 [ Problem initially found on Windows-10, using :
         ffmpeg version N-77681-gb6c61b7 Copyright (c) 2000-2016 the FFmpeg
 [ On my Debian-family-based Linux, I have version 2.8.3 of FFMPEG, which I
 also validated these findings against. ]

 To pad, I followed this tutorial:

 [ Some other FFMPEG pad info, such as this one, erroneously claim that you
 first need to 'scale', but that makes NO sense at all! ]
 VLC can pad without scaling first, so FFMPEG should be able to, too. The
 VLC clause needed is simply:
 and note that VLC, unlike FFMPEG, is transparent to what the initial/final
 resolutions happen to be !

 So using the pad-filter, I padded it via ffmpeg, from 720x480 to 720x540,
 with extra 30 top and bottom.  [ It took 7 minutes. ]
         ffmpeg -i Raising_Arizona-3mins.mkv  -filter:v
 pad=720:540:0:30:black Raising_Arizona-ffmpeg-pad.mp4
 Note that FFPEG's pad creates the output into H264 (whether you wanted
 that or not).

 Then, I did the same pad, using VLC.  It took only 2 minutes.  [ Note that
 with VLC I'm using vcodec=mpeg4, not h264. To go to h264, takes 12 mins.]
         vlc -vvv  --extraintf logger --fullscreen --play-and-exit --no-osd
 --no-sub-autodetect-file --log-verbose=2 --verbose-objects=+all

 So I learned from this:  Staying in MPEG2 or MPEG4 (until the final pass,
 where h264 is required for us), is the way to go.  It is MUCH faster.

 i.e I learned that FFMPEG's PAD filter REQUIRES them to put the output
 into h264 (which is what is slowing their padding time down). I also
 found that when the INPUT file is already in h264, FFMPEG thinks it needs
 a bunch more stuff, like "-pix_fmt"..which appears to be broken.

 Also, VLC is totally transparent to what the initial/final resolutions
 are, whereas FFMPEG requires you to phrase your request explicitly stating
 the target resolution.

Ticket URL: <https://trac.ffmpeg.org/ticket/5123>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker

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