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

[Iban Garcia]

Hi everybody,

After testing downconversion from 1080i to 576i, I am trying now to find
the best way to convert HD-720p 50fps progressive contents to 25fps
(50fields per second) 576i SD.
I need a DVCPRO25 interlaced content in the output.

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 [?])

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*

So, I use "interleave_bottom" to extract only one field from each frame
(top field, down field, top field, down field...), and creating a new frame
from these two fields.


The *PROBLEM* I am trying to solve is ALIASING. These links contains what
happens exactly:
1) where high detail in HD -->in SD noise after downscaling (doc:
http://pcgamingwiki.com/wiki/Anti-Aliasing_%28AA%29)
2) where clear borders in HD --> in SD "staricase effect" in those borders
after downscaling (doc: http://www.svi.nl/AntiAliasing)


So, I think the best way is to applying a "Antialiasing Filter" in
someway...

The *QUESTION*s are:
1) Is it possible to insert into -vf string something about antialiasing
filter?
2) I have tried to use "-sws_flags lanczos" and "-sws_flags bilinear"
inside the command above, but no improvement detected at all... [?]


Many thanks in advance!!!

Iban



COMPLETE CONSOLE OUTPUT WHEN EXECUTING...
 built on Oct  3 2012 12:42:45 with gcc 4.5 (SUSE Linux)
  configuration: --shlibdir=/usr/lib64 --prefix=/usr/local
--mandir=/usr/share/man --libdir=/usr/local/lib --enable-pthreads
--enable-shared --enable-libvorbis --enable-gpl --enable-x11grab
--enable-libx264 --enable-libmp3lame --enable-postproc --enable-nonfree
--arch=x86_64 --cpu=64
  libavutil      51. 73.101 / 51. 73.101
  libavcodec     54. 63.100 / 54. 63.100
  libavformat    54. 29.105 / 54. 29.105
  libavdevice    54.  3.100 / 54.  3.100
  libavfilter     3. 19.102 /  3. 19.102
  libswscale      2.  1.101 /  2.  1.101
  libswresample   0. 16.100 /  0. 16.100
  libpostproc    52.  1.100 / 52.  1.100
[mxf @ 0x633240] invalid KAGSize 0 - guessing 1
[mxf @ 0x633240] invalid KAGSize 0 - guessing 1
Guessed Channel Layout for  Input Stream #0.1 : mono
Guessed Channel Layout for  Input Stream #0.2 : mono
Guessed Channel Layout for  Input Stream #0.3 : mono
Guessed Channel Layout for  Input Stream #0.4 : mono
Guessed Channel Layout for  Input Stream #0.5 : mono
Guessed Channel Layout for  Input Stream #0.6 : mono
Guessed Channel Layout for  Input Stream #0.7 : mono
Guessed Channel Layout for  Input Stream #0.8 : mono
Input #0, mxf, from '/net/localhost/biltegia/original_video.mxf':
  Metadata:
    timecode        : 00:00:00:00
  Duration: 01:24:00.00, start: 0.000000, bitrate: 123172 kb/s
    Stream #0:0: Video: h264 (High 4:2:2 Intra), yuv422p10le, 1280x720 [SAR
1:1 DAR 16:9], 50 fps, 50 tbr, 50 tbn, 100 tbc
    Stream #0:1: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
    Stream #0:2: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
    Stream #0:3: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
    Stream #0:4: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
    Stream #0:5: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
    Stream #0:6: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
    Stream #0:7: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
    Stream #0:8: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
Output #0, dv, to '/net/localhost/biltegia/output_file.dv':
  Metadata:
    timecode        : 00:00:00:00
    encoder         : Lavf54.29.105
    Stream #0:0: Video: dvvideo, yuv411p, 720x576 [SAR 64:45 DAR 16:9],
q=2-31, 200 kb/s, 90k tbn, 25 tbc
    Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (h264 -> dvvideo)
  Stream #0:1 -> #0:1 (pcm_s24le -> pcm_s16le)
Press [q] to stop, [?] for help
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