[FFmpeg-user] When to determine frames are progressive or interlaced ?

[Carl Eugen Hoyos]

Christian Ebert <blacktrash <at> gmx.net> writes:

> > I suspect (and it is what James writes above) that mediainfo 
> > only tells you if the video was encoded using an encoder 
> > setting "interlaced" or not. It does not tell anything about 
> > the actual content.
> > If you use a deinterlacer on progressive content (no matter 
> > if it was encoded as "interlaced" or not), you permanently 
> > damage the frames. Otoh, you can encode interlaced material 
> > as "progressive" (or use an encoder that does not support 
> > "interlaced") and only visual inspection or a filter like 
> > idet will tell you if you should use a deinterlacer or not.
> 
> The result by mediainfo coincides with my visual inspection - I
> can see it right away when I play the files in mplayer without
> yadif: blatantly obvious vertical lines in the picture - with
> yadif the picture is fine. Encoding without deinterlacing looks
> just awful.

So I stand corrected, maybe the reason is that most of my 
experience is with Transport Stream where I know as a 
fact that they typically signal "interlaced" even for 
progressive material, maybe this simply does not 
happen for DVD's.

> I also have the reverse case: PAL movs processed with the Bitvice
> denoise filter, which also offers a deinterlace option: no
> deinterlacing needed. Again mediainfo confirms my visual
> inspection, idet is neither here nore there when it comes to the
> decision whether I should deinterlace or not.

I am not sure I understand this sentence:
Do you mean that you tested the idet filter and it gives wrong 
results for the tested files or do you mean you just did not 
need it because you did not have a file where mediainfo failed?

[...]

> I can't argue with the theoretical background

Note that I was on the contrary only talking about 
practical issues ("is the video content interlaced 
or not"?), not the theoretical base ("was an 
encoder setting "interlaced" used or not?).

Do you have access to any random DVB streams?
Does mediainfo correctly tell if they are interlaced 
or not?

Carl Eugen