[linux-dvb] Re: Mplayer aspect ratios

[Joachim Steiger <roh@hyte.de>]

On Wed, 18 Jun 2003, Ashley Evans wrote:

> > >When I fullscreen 4:3 broadcasts I have black borders around all of the
> > > image. Is there anyway to make mplayer automatically crop and scale?

> > My mplayer automatically scales whatever I fit to fill the window... for
> > 16:9 stuff it opens a 16:9 window by default... for 4:3 it opens a 4:3
> > window..

> I have xv. I don't think it's actually an mplayer problem. When I view (Top of
> the Pops 2 as a current example) The mpeg stream is 720x576 but the picture
> is in 4:3 ratio so there are black bars encoded in the mpeg stream, either
> side of the actual picture. Hence when this is maximised I have black borders
> around each edge of the picture.

first thing: the mpeg is NOT square-pixels!
you need to scale the 720x576 to 768x576 to get correct aspect ratio.
the 'black borders' are normal since a normal tv crops them in hardware..
the actual pal (or ntsc, the same game but just with 640x480) has more
content than a normal tv displays... there are e.g. the vbi lines for
videotext or vps as well as broadcaster-side stuff like timecodes for
maz-machines
this 'data-in-picture-lines' should be blanked with black from the
broadcaster before encoding and broadcasting... but as usual some do not
care bout standards and so it happens that you see timecodes between you
picture and the black border above your picture when viewing a 16:9
transmission on a 4:3 tv and let the set-top-box do the letterbox-thingie
for you

to your problem: the black borders are not always the same size... but the
most of the 'undisplayed' content on your tv actually belongs to the
picture.. so you actually get more (a little bit) viewing angel than a
normal tv-user ;)

roh

ps: i think it was called 'overscan' but i'm not perfectly shure bout this



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