[MEncoder-users] Xvid bff/tff field order issue

[Oliver Muth]

Hi,

when transcoding an interlaced mpeg-2 file (DVB-T capture) to Xvid ASP5, the output is always bottom field first, no matter what I do, even though the input is top field first. At least mediainfo reports tff for the mpegs and bff for the Xvids.

The resulting videos I take with me to watch them on an analog TV (that's why I keep them interlaced).
Most of the time they look fine, but sometimes I get awfull jitter in high motion scenes. Quickly moving objects seem to kind of bounce back and forth.

Attempts to cure the problem:
A. pre-pending il=s to the filter list partly works: No bouncing, but the video seems to flicker slightly.
B. yadif=0 works, too - but I wanted to keep it interlaced.
C. pre-pending phase=t - yes, thatś it! Looks nice.
(Of course on a progressive display they would all look the same.)

Now my questions:

1. Why am I not seeing this effect with all movies? All input files are reported to be tff by mediainfo. Is that wrong? Or am I just occasionally blind, or the effect is almost invisible in movies with slower motion?
2. What's happening? I assume that after encoding with Xvid the movie is still tff, only the flag is set to bff. When I transcode back to mpeg2 everything looks fine again.
3. Could someone please explain (in simple words) the difference between il=s and phase=t? Does il=s just switch the fields within the same frame, while phase=t pushes the bottom field into the next frame? Why does it flicker with il=s?
4. Would it be safe to add "phase=t" to my standard profile?
Or would I destroy those movies that otherwise were transcoded fine?

Thanks in advance for your answers

Oliver


My mencoder command line:
mencoder -profile "Xvid-asp5-avi-1" -o out.avi in.mpg

The mencoder profile:
[Xvid-asp5-avi]
profile-desc="Xvid/MP3 MPEG4 ***@L5 encoding constant quantiser"
ovc=xvid=1
xvidencopts=profile=asp5:fixed_quant=4:vhq=4:quant_type=mpeg:chroma_opt=1:threads=2:autoaspect=1:interlacing=1:psnr=1
vf=il=d,hqdn3d=2:1:2,il=i,harddup=1
oac=mp3lame=1
lameopts=vbr=3

System: Debian Squeeze with debian-multimedia repositories.

[D***@habmalnefrage.de]

Hi,

here an update to this topic:

- I forgot to mention that the movies are in PAL format.

- The exact same issue was discussed on this list already before:
http://lists.mplayerhq.hu/pipermail/mencoder-users/2010-March/011334.html
However, no solution for mencoder/xvid was suggested (other than to change the codec).

- I have made a few more tests with different files, all tff.
Results: Mencoder/xvid does not honor the field order, regardless which field-dominance=0 or =1 is passed to it. The resulting files are identical (same md5sum) and all bottom field first.

- The problem applies to all PAL movies I tested. Even in those I mentioned in my previous posting, where the effect is not easily visible due to many still pictures or slow motions, the effect is there: e.g. subtitles flicker. When they fade in, they are shown for a split second, then disappear for a split second and then stay for good.

- Bug?
Since mencoder when used with the xvid codec and basic options as given in the manual completely screws up good, working PAL movies, I think it's safe to call this a bug. ;-)

- Solution?
The only solution I found so far is: -vf phase=t

I'm not an expert. So I don't know whether this is a perfect solution.
Could any of the experts please let me know whether it has any drawbacks?

The results look fine to me, but this may be due to the low quality of either my video files, my analog TV, or my eyes. ;-)


One more question:
Is there any way to change the field order flag in an already encoded AVI?
Without introducing further quality losses by re-encoding?
With mencoder or another Linux-tool?

Thanks in advance

[D***@habmalnefrage.de]

When I wanted to open a bug report I noticed one already exists concerning this topic.
( http://bugzilla.mplayerhq.hu/show_bug.cgi?id=1786 )

Surprisingly, when I tried both patches suggested there
NONE of them worked for me.

Now I am lost.
With both patches mencoder produces videos that are flagged tff as they should be. Good.
Everything looks fine - until I play them on my analog TV.
They are just as jumpy as the bff ones were before.

What? Why?

Is this still a mencoder problem?
Or does my hardware DVD-player assume all Xvid-videos to be bff and thus does not honor the tff flag?
I am confused.

Could somebody please do me the favor to check out these 10 sec. video clips ?
And let me know whether they play fine on your interlaced TV?

H_.mpg (7.14MB) is the original tff PAL input file. It plays fine on my computer as well as on my TV.
H_fd0.avi (2.99MB) is bff encoded with mencoder -ovc xvid -xvidencopts profile=asp5:.... without -vf phase=t
H_new.avi (2.99MB) is tff encoded with the patched mencoder.

Both AVIs play fine on my progressive display but jumpy on my analog TV.

http://rapidshare.com/files/447175514/H_.mpg
http://rapidshare.com/files/447190604/H_fd0.avi
http://rapidshare.com/files/447531027/H_tff.avi

You can get the same files also from here:
http://www.gmx.de/mc/ifMk1jX7JH5fNrXBqPQplFOdUNVIfz

I would very much appreciate any hints, ideas, advice...

[Jarek Czekalski]

I posted a patch that inserts tff flag into xvid. I posted even a patch
showing tff/bff flag while playing videos. The crew was not interested
in fixing this entry. Generally they don't care about interlacing videos.

Although I was not satisfied with ignoring my work, I finally decided to
switch to non-interlaced archives. They convinced me to do so and now I
have better quality movies than before. Still I have my mplayer
corrected to be able to encode tff xvid.

Now I noticed gmane search engine doesn't work well and even it ignores
my posts. This problem is reported in another mail.

You can see my 4 posts regarding xvid interlacing on archive of Sep 2010.
http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2010-September/author.html

Jarek

Post by D***@habmalnefrage.de
When I wanted to open a bug report I noticed one already exists concerning this topic.
( http://bugzilla.mplayerhq.hu/show_bug.cgi?id=1786 )
Surprisingly, when I tried both patches suggested there
NONE of them worked for me.
Now I am lost.
With both patches mencoder produces videos that are flagged tff as they should be. Good.
Everything looks fine - until I play them on my analog TV.
They are just as jumpy as the bff ones were before.
What? Why?
Is this still a mencoder problem?
Or does my hardware DVD-player assume all Xvid-videos to be bff and thus does not honor the tff flag?
I am confused.
Could somebody please do me the favor to check out these 10 sec. video clips ?
And let me know whether they play fine on your interlaced TV?
H_.mpg (7.14MB) is the original tff PAL input file. It plays fine on my computer as well as on my TV.
H_fd0.avi (2.99MB) is bff encoded with mencoder -ovc xvid -xvidencopts profile=asp5:.... without -vf phase=t
H_new.avi (2.99MB) is tff encoded with the patched mencoder.
Both AVIs play fine on my progressive display but jumpy on my analog TV.
http://rapidshare.com/files/447175514/H_.mpg
http://rapidshare.com/files/447190604/H_fd0.avi
http://rapidshare.com/files/447531027/H_tff.avi
http://www.gmx.de/mc/ifMk1jX7JH5fNrXBqPQplFOdUNVIfz
I would very much appreciate any hints, ideas, advice...

[D***@habmalnefrage.de]

Hi Jarek,

Great to hear from you!
So far the silence has been overwhelming... ;-)

Thank you for the link to your posts. I found your bug report (though google wouldn't find it), but not your other patches.
I'll try them out.
None of them seems to be in the current SVN mencoder. Not even the patch Reimar posted as response to your bug report 1786...?

Why wouldn't they be interested in interlaced videos?
All my sources (DVB) are interlaced. My target TV is interlaced.
So how did they convince you to switch?


Did you have a chance to check out my three video clips?
Do those AVIs play jittery on your TV as well?
How would you create a reasonable quality Xvid video from that mpeg-2 file?
Without jitter?
I only succeeded with -vf phase=t.

[Jarek Czekalski]

Post by D***@habmalnefrage.de
So how did they convince you to switch?

Search last 10 months of this group (and devel) against yadif or
kerndeint. You'll find explanation. Shortly speaking: mpeg4 is targeted
at non-interlaced content and it does not perform well on interlaced.
Make tests, you'll see.

The remaining questions are not to me.

Regards
Jarek

[Moritz Barsnick]

Post by D***@habmalnefrage.de
Everything looks fine - until I play them on my analog TV.
They are just as jumpy as the bff ones were before.

[...]

Post by D***@habmalnefrage.de
Could somebody please do me the favor to check out these 10 sec. video clips ?
And let me know whether they play fine on your interlaced TV?

[...]

Post by D***@habmalnefrage.de
Both AVIs play fine on my progressive display but jumpy on my analog TV.

Same here.

I have a classic "SD" interlaced CRT TV set. I fed these files to my
(HD capable) HDD receiver's media player, which I assume can output
interlaced content as interlaced on the SD baseband output. And indeed,
the original file looks fine, both AVIs look very jumpy.

(I didn't go to the trouble to put those files onto a compliant DVD.
With my DVD player, I would be more sure that interlaced content is
passed to the TV straight interlaced without intervention.)

While deinterlacing seems to be recommended by every one, I agree that
if your content is already interlaced, and your playback device is
(forced to be) interlaced, it would be a good idea to keep the content
that way without intermediate deinterlace. UNLESS you need to change
resolution, and perhaps also taking the MPEG4 comment into account. I
also want to do some analog captures to disk, and burn them to DVD
while keeping them interlaced. Alas, I have yet to find the absolutely
correct capture and conversion settings for mencoder and ffmpeg. :)

Moritz

[D***@habmalnefrage.de]

Post by Moritz Barsnick
I have a classic "SD" interlaced CRT TV set. I fed these files to my
(HD capable) HDD receiver's media player, which I assume can output
interlaced content as interlaced on the SD baseband output. And indeed,
the original file looks fine, both AVIs look very jumpy.

Thank you!
At least my dvd-player is Ok then.

But this means that mencoder - with or without patch - is simply not capable of encoding interlaced PAL source files with the xvid codec??
That's a shame!

Especially since my dvd-player rejects libav encoded mpeg4. I have not yet figured out why...

Post by Moritz Barsnick
While deinterlacing seems to be recommended by every one,

Well, some do some don't.
In this old thread http://lists.mplayerhq.hu/pipermail/mencoder-users/2007-October/007217.html
you seem to be on the "don't deinterlace" side yourself. ;-)
So was Reimar: http://lists.mplayerhq.hu/pipermail/mencoder-users/2007-September/007023.html

Maybe this is just like: If you are interested enough in video encoding to volunteer to write encoding software, then you are interested enough to buy yourself a fancy big ultra HD plasma TV and just don't care about interlaced content. ;-)

However, if all your sources are interlaced and all your hardware (only) supports interlaced content, then I don't see the point in wasting processing power and time on a deinterlacing filter.
Only to get fewer pictures per second...?

Post by Moritz Barsnick
I also want to do some analog captures to disk, and burn them to DVD
while keeping them interlaced. Alas, I have yet to find the absolutely
correct capture and conversion settings for mencoder and ffmpeg. :)

The main reason why I bought a capture card was to "secure" my VHS collection.
So far the best solution I found was to capture losslessly as ffv1 in a matroska container, like in this profile:
[VHS-roh]
profile-desc="capture losslessly from VHS"
tv=driver=v4l2:normid=5:quality=0:width=768:height=576:fps=25:freq=601.125:alsa=1:adevice=hw.1:amode=1:forceaudio=1:immediatemode=0:audiorate=48000
oac=lavc=yes
ovc=lavc=yes
lavcopts=vcodec=ffv1:acodec=ac3:abitrate=192:threads=2
of=lavf=yes
lavfopts=format=matroska
srate=48000
ofps=25
vf=harddup=1
noskip=1
endpos=1:31:00

This allows for 2-pass encoding or experimenting with filters, without having to re-play an ageing tape on an ageing player again and again.

Videos I'll probably only watch on a computer I encode as x264/matroska.
For a DVD with a nice menu I scale to 352x576 interlaced, playable on any DVD-player.
I feel that this is enough resolution for an old low quality VHS (which is not 720x576 anyway).
mencoder -oac copy -ovc lavc -lavcopts \ vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=8500:ilme=1:ildct=1:keyint=15:vstrict=0:trell=1:mbd=2:autoaspect=1:threads=2:psnr=1 .....\
-vf crop=704:576:8:0,il=d,hqdn3d=2:1:2,il=i,scale=352:576:1
...

[James Hastings-Trew]

Post by D***@habmalnefrage.de

Post by Moritz Barsnick
I have a classic "SD" interlaced CRT TV set. I fed these files to my
(HD capable) HDD receiver's media player, which I assume can output
interlaced content as interlaced on the SD baseband output. And indeed,
the original file looks fine, both AVIs look very jumpy.

Thank you!
At least my dvd-player is Ok then.
But this means that mencoder - with or without patch - is simply not capable of encoding interlaced PAL source files with the xvid codec??
That's a shame!
Especially since my dvd-player rejects libav encoded mpeg4. I have not yet figured out why...

Have you tried setting the ffourcc value of the AVI, rather than letting
it be the default? Try -ffourcc XVID or -ffourcc DIVX or -ffourcc DX50
on your command line when encoding and see if any of those make your
dvd-player happy. I believe the default ffourcc code is FMP4 or
something, which nearly nothing understands properly.

[Jarek Czekalski]

Muth, I pointed you to a patch that works.

http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2010-September/066257.html

If you didn't try it, don't say "with or without a patch".

Post by D***@habmalnefrage.de
But this means that mencoder - with or without patch - is simply not
capable of encoding interlaced PAL source files with the xvid codec??
That's a shame!