[FFmpeg-user] ffmpeg added letterbox, change ration, without -aspect nor -vf pad. strange.

Zhang Weiwu zhangweiwu at realss.com
Mon Jan 30 08:12:24 CET 2012

于 2012年01月30日 14:59, Zhang Weiwu 写道:
> To my surprise, mplayer plays back the resulting file with both
> letterbox and wrong aspect (stretched to 384x288). 

Further experiment shows this behaviour only happen to 3gp files. If I
only change the output file's ending to .mp4, all is well expected:
aspect being wrong and no letterbox. From here, to correct aspect by
adding letterbox is easy.

More observation shows mplayer playback my home-brew CIF-size 3GP movies
in 384x288(4:3), adding letterbox left and right, instead of or despite
stretching. This is a hint that 3GP format expects its player's viewport
to be 4:3. Now the question is, is this a unified specification? Should
I expect 352x288 movie in 3gp USUALLY played back with a viewport of 4:3
on mobile phone LEDs? Stretched? With letterbox?

Thanks in advance!

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