[FFmpeg-user] Best way for converting HD 1080i to DVCPRO25 DV?

[Francois Visagie]

> -----Original Message-----
> From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-
> bounces at ffmpeg.org] On Behalf Of Andy Furniss
> Sent: 04 September 2012 21:49
> To: FFmpeg user questions
> Cc: Iban Garcia
> Subject: Re: [FFmpeg-user] Best way for converting HD 1080i to DVCPRO25
> DV?
> 
> Iban Garcia wrote:
> > Hi,
> >
> > I go on with searching the best way to convert HD-1080i content to
> > SD-576i content, with losing the minimun detail... :-O
> >
> > Well... I have making some new tests... but when transcoding from HD
> > 1080i to SD-PAL the video loses a lot of detail (i.e., 720x576i video
> > is a little bit blurred)
> >
> > I have tested with this option UNSHARP filter in order to get a
> > SHARPer SD
> > content: $comando="ffmpeg -y -threads 8 -i ".$input_file.".mxf
> > -pix_fmt yuv411p -aspect 16:9 -vf
> > \"scale=720:576:interl=1,fieldorder=bff,unsharp=7:7:2.5\" -vcodec
> > dvvideo -map 0:v -map 0:a:2 -ac 2 ".$output_file.".dv";
> >
> > But there is a problem... unsharp filter is acting with frames and not
> > with fields. So, the video after filtering gets a wrong output:
blinking.
> >
> > Is there any way to use "sharp filter" with fields and not with frames?
> >
> > Many Thanks in advance!!
> 
> I'm still not sure that sharpening is a good idea on interlaced, but it's
not my
> video and I suppose it's more likely not to be played on a "real"
interlaced
> display than in the past.

I agree.

If you absolutely MUST sharpen, what usually works best is to use a
specialist deinterlacer > sharpen > re-interlace. A good example of such an
interlacer would be Avisynth's QTGMC.

But in my limited experience with DV, perceived loss of detail is usually
caused by less-than-optimal resizing or (unexpected) colourspace conversions
and/or imagination! Remember, chances are you're watching the interlaced
output on a progressive display as suggested by Andy. With a player lacking
dedicated interlaced support this will make the output look worse than it
is.

> 
> Prompted by this thread I had a look at what the BBC scale was like by
> recording HD and SD channels showing F1 at the same time.
> 
> TBH their SD looked quite soft and I could get something sharper looking
at
> the same bitrate just using lanczos.
> 
> For some strange reason my version also deinterlaced better than theirs
>   - I maybe lucked into that one. Sometime I am going to repeat and see.
> 
> 
> 
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