[FFmpeg-user] Remove two lines from the bottom of the video

[Wesley Wen]

On Mon Feb 02 2015 at 8:51:23 PM Moritz Barsnick <barsnick at gmx.net> wrote:

> Hi Wesley,
>
> On Mon, Feb 02, 2015 at 10:51:12 +0000, Wesley Wen wrote:
> >     Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p,
> 426x240 [SAR 149:181 DAR 10579:7240], 80 kb/s, SAR 12800:15549 DAR 320:219,
> 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
>
> I have always found those AR numbers a little peculiar, but refused to
> look at the code creating them. ;-)
>
> But this results from your scaling to 426x240, not from the cropping.
>
> > Input #0, mpeg, from 'sample.mpg':
> >   Duration: 00:24:28.18, start: 0.262000, bitrate: 8597 kb/s
> >     Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv), 720x480
> [SAR 8:9 DAR 4:3], 8000 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
> >     Stream #0:1[0x1c0]: Audio: mp2, 48000 Hz, stereo, s16p, 384 kb/s
> >
> > And here is the command I used to do crop.
> > ffmpeg -y -i sample.mpg -c:v libx264 -b:v 80k -vf
> crop=720:438:0:0,scale=426:240 out.mp4
>
> Excuse me? You write you want to remove two lines, but you are removing
> 42. Nice number, but different result! (480 - 438 = 42.) Did you
> complain about the non-4:3 AR, or that your image is peculiarly
> stretched? The latter would be due to your miscalculation.
>
> > I'd like to keep display aspect ratio as 4:3, and remove those two green
> > lines or fill black.
>
> Well if you snip away something in one dimension, you are going to ruin
> the aspect ratio. So you either need to snip accordingly in each
> dimension (e.g. 4 columns horizontally, 3 lines vertically), or stretch
> to refill the original dimensions, or fill up with something else such
> as black.
>
> Since filling with black is okay for you, let me suggest cutting away
> (i.e. "crop"ping) and filling back up (i.e. "pad"ding):
>
> $ ... -vf "crop=720:478:0:0,pad=720:480:0:0,scale=426:240"
>
> Thank you Moritz!
It resolves the issue. :-)

-Wesley


> (I think both former filters default to ":0:0", check the docs.)
>
Let us know if this helps,
> Moritz
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