[FFmpeg-devel] Bug in FFMPEG video filter TINTERLACE needs fixing

[Paul B Mahol]

You have setfield and similar filters that can be used before this filter.

On 7/12/20, Ben Hutchinson <benhut1 at gmail.com> wrote:
> Problem is it's not as simple as just patching it to start at field 1
> instead of field 2. It really depends on your signal source. If your signal
> source recorded all lines that contain at least some image signal (even if
> only half the line contains image signal), then the top line of the image
> is the first line of field 2 (the even field). However, if your signal
> source only recorded lines where the entire line contains image signal then
> the top line of the image is the first line of field 1 (the odd field).
> When using the TINTERLACE video filter (at least in MERGEX2 mode), one
> actually needs to be able to select which field comes first (odd field
> first, or even field first). This unfortunately is a much more in-depth
> patch to the software than just hardcoding a different starting field. You
> will need to add commandline option for the TINTERLACE filter in FFMPEG in
> order to allow for user-selection of OFF or EFF.
>
> On Sun, Jul 12, 2020 at 9:10 AM Paul B Mahol <onemda at gmail.com> wrote:
>
>> On 7/12/20, Ben Hutchinson <benhut1 at gmail.com> wrote:
>> > I was assuming it started from 1, because in the NTSC video standard
>> (which
>> > is of course where the concept of interlaced video originated), the
>> > first
>> > field is called field 1. Field 1 contains the first full line of
>> displayed
>> > video (though technically field 2 contains the first image data, one
>> > line
>> > above the first displayed line of field 1, although it's only the right
>> > half of that line).
>>
>> I sent patch to fix this.
>>
>> >
>> > On Sat, Jul 11, 2020 at 4:07 AM Paul B Mahol <onemda at gmail.com> wrote:
>> >
>> >> On 7/11/20, Ben Hutchinson <benhut1 at gmail.com> wrote:
>> >> > I was reading it directly from the official FFMPEG website.
>> >> > https://ffmpeg.org/ffmpeg-filters.html
>> >> > All the info about the TINTERLACE filter I got from reading the info
>> >> there.
>> >> >
>> >>
>> >> OK, lets try again, where have you read that first frame is always an
>> >> odd frame, one with 1 number.
>> >> FFmpeg counts from 0.
>> >>
>> >> > On Fri, Jul 10, 2020 at 2:14 AM Paul B Mahol <onemda at gmail.com>
>> wrote:
>> >> >
>> >> >> On 7/8/20, Ben Hutchinson <benhut1 at gmail.com> wrote:
>> >> >> > According to the documentation on the TINTERLACE video filter, the
>> >> >> > filter
>> >> >> > mode called MERGEX2 will "Move odd frames into the upper field,
>> even
>> >> >> > into
>> >> >> > the lower field, generating a double height frame at same frame
>> >> >> > rate."
>> >> >> But
>> >> >> > it doesn't do this, at least in some cases (not sure about all
>> >> >> > cases).
>> >> >> The
>> >> >> > first frame in a sequence should be considered frame one (an odd
>> >> frame)
>> >> >> for
>> >> >>
>> >> >> Where is this written?
>> >> >>
>> >> >> > the purpose of this interlacing algorithm. However, that is not
>> >> >> > what's
>> >> >> > happening in my experience. At least with raw video (using "-f
>> >> >> > rawvideo")
>> >> >> > it's treating the first frame as frame zero (an even frame) and
>> thus
>> >> my
>> >> >> > first frame (which contains top-field data) ends up getting put
>> into
>> >> the
>> >> >> > bottom-field of the output video, and this is messing up the
>> output.
>> >> >> Please
>> >> >> > fix this.
>> >> >> > _______________________________________________
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>> >> >> > ffmpeg-devel at ffmpeg.org
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>> >> >> >
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