[noggin]

*** EDIT - I had deinterlace set to ON, not AUTO. If you have it to AUTO things work !***

Looking at https://github.com/xbmc/xbmc/blob/6ffe6d...FFmpeg.cpp Line 486 has the correct YADIF parameters for a source field->output frame conversion, which will be 50i to 50p.

Code:

m_filters_next = "yadif=1:-1";

What parameters are you sending? If you are sending

Code:

m_filters_next = "yadif=0:-1";

that will be source frame->output frame conversion which will be 50i to 25p.

https://ffmpeg.org/ffmpeg-filters.html#yadif-1 has the YADIF config for ffmpeg

Code:

9.154 yadif
Deinterlace the input video ("yadif" means "yet another deinterlacing filter").

It accepts the following parameters:

mode
The interlacing mode to adopt. It accepts one of the following values:

0, send_frame
Output one frame for each frame.

1, send_field
Output one frame for each field.

2, send_frame_nospatial
Like send_frame, but it skips the spatial interlacing check.

3, send_field_nospatial
Like send_field, but it skips the spatial interlacing check.

The default value is send_frame.

parity
The picture field parity assumed for the input interlaced video. It accepts one of the following values:

0, tff
Assume the top field is first.

1, bff
Assume the bottom field is first.

-1, auto
Enable automatic detection of field parity.

The default value is auto. If the interlacing is unknown or the decoder does not export this information, top field first will be assumed.

deint
Specify which frames to deinterlace. Accept one of the following values:

0, all
Deinterlace all frames.

1, interlaced
Only deinterlace frames marked as interlaced.

The default value is all.

So you want parameters of "1:-1" (to do a 2x YADIF on frames that are detected as interlaced, and automatically detect top field or bottom field first)