[FFmpeg-user] Interlaced frames not recognized as such

[Robert Krüger]

On Fri, Apr 25, 2014 at 5:27 PM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> Robert Krüger <krueger <at> lesspain.de> writes:
>
>> Summary: Frames from an interlaced file created using ffmpeg's
>> tinterlace and fieldorder filters are not recognized as interlaced by
>> ffmpeg.
>
> Did you test the idet filter?
> Only this filter (of FFmpeg's features) can tell you if the *content*
> of a video stream is interlaced or progressive (the filter can not
> yet identify telecined content, it is probably not very difficult to
> add this).

I am making the interlaced file artificially on purpose for testing,
so I know what content will be in there in this case and there I am
interlacing progressive frames (again on purpose).

>
>> Now I wonder if I used the wrong CL for creating the file or
>> if interlaced detection fails in this case.
>
>> I created an interlaced file by this command line (full output included):
>
> Just to clarify:
> You created a progressive MPEG-2 stream showing interlaced frames.
>
>> ffmpeg -i color_frames_png_1080_50p.mov -vf
>> "tinterlace=interleave_top,fieldorder=tff" -vcodec mpeg2video -q 1
>> -pix_fmt yuv422p -r 25 -y color_frames_mpeg2_1080_50i_tff_3f.mov
>
> There is an option to create an interlaced MPEG-2 stream but you did
> not use it (-ilme -flags +ildct), so a progressive stream was created...

sh....! Of course, -flags +ildct was missing. Just hadn't done that on
the CL for a long time.

Thanks a lot for the quick help. Works a expected now.

>
> Unrelated:
> Old MEncoder documentation suggests never to use -qscale 1 but
> -qscale 2.

Oh, that's news to me. I have been using 1 whenever I wanted highest
quality possible. I didn't find the values documented however (I just
looked at http://ffmpeg.org/ffmpeg.html).


>
>> interlaced_frame=0
>
> which is reported by ffprobe.
>
> Note that ffprobe will report "interlaced_frame" for a (sd) dvb recording
> no matter how progressive the content is.
> (Our tv providers always flag "interlaced")
>
>> The file is reported as interlaced by ffmbc, mediainfo if anyone
>> cares to know.
>
> Sounds like a bug to me.

I think they use the container metadata and the resulting mov file
indeed has the fiel atom set to interlaced content.

Regards and thanks,

Robert