[FFmpeg-user] Converting from HD (720p) to SD (576i)

[Iban Garcia]

2012/10/10 Carl Eugen Hoyos <cehoyos at ag.or.at>

> Iban Garcia <ibantxo28 <at> gmail.com> writes:
>
> > The process complains two main "to do"s:
> > 1) RESIZE (from 1080x720 to 720x576)
> > 2) INTERLACE: Creating an interlace content from a
> > progressive content (but with double frame rate [?])
>
> (This should be "half frame rate" in my understanding,
> and that is what you use below.
>
> You have understood very well, Carl, I wanted to explain (may be I did not
do it clearly [?][?] ):
SOURCE: HD 1080x720p 50fps
DESTINATION: SD 720x576i 25fps

>
> > The command I have used is the next one:
> >
> > *ffmpeg -i original_video.mxf -threads 8  -pix_fmt -pix_fmt yuv411p
> > -aspect 16:9 -vf "scale=720:576,tinterlace=interleave_bottom,
> > fieldorder=bff" -ac 2 -y -r 25 output_file.dv*
>
> (Isn't there a copy-paste error in the first line?)
>
> Yes... it has been a paste error. The first command was:
ffmpeg -i original_video.mxf -threads 8  -pix_fmt -pix_fmt yuv411p -aspect
16:9 -vf "scale=720:576,tinterlace=interleave_bottom,fieldorder=bff" -ac 2
-y -r 25 output_file.dv


> I may be wrong (and I did not test), but it may make
> a difference at what time the colour space conversion
> happens.
> (This should be visible with some -loglevel, it may
> have been a bad idea that the filter system stopped
> to be verbose about what exact filters are used.)
>
> Perhaps try filter "format=yuv411p" instead of -pix_fmt?
>
> I am trying now with this "format" advice. But if used previous "-pix_fmt
yuv411p" command, some colour difference is detected between "HD source"
and "SD transcoded".



Strojan advice: using filters in other way... The resoult is quite good for
"border effect" (i.e. "staircase effect" is not so exagerated as before)
but... [?] there is a extrange effect when there is movement inside video.
It is not "interline twitter" or "inversed fields" effect. The movement is
not so natural... It is strange because interleave_bottom theorically uses
the same concept than PAL. Umm... May be interleave_top must be used
instead of interleave_bottom...? umm...
Using Strojan advice I obtain a resoult where "high frequencies noise after
downscaling" is very decreased.

Thanks Strojan and Carl. Some advice will be welcome!!! :-)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/gif
Size: 100 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-user/attachments/20121011/8dddb9ee/attachment.gif>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/gif
Size: 611 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-user/attachments/20121011/8dddb9ee/attachment-0001.gif>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/gif
Size: 96 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-user/attachments/20121011/8dddb9ee/attachment-0002.gif>