Best practice video capturing from VHS

...what?

If you're not rescaling vertically, and you want an interlaced result from an interlaced source, then you shouldn't need to deinterlace/interlace - just rescale.

There should be no need to deinterlace and reinterlace in this scenario as you aren't doing any vertical scaling, just horizontal.

However you will probably need to persuade ffmpeg to keep the output interlaced. if you use -vcodec libx264 -flags +ildct+ilme that should keep things interlaced.

The only reason to deinterlace is if you are doing a vertical scale. (You can scale in the field rather than frame domain with interlaced content using an interlace aware scale but the quality can be reduced if you do)

However do you want to rescale 544x576 to 720x576 or do you want a square pixel result?

Well in this case the source is 544x576 4:3 interlaced so the result I ideally need is 720x576 4:3 interlaced

OK - if you're going for DVD, or a playback solution that can cope with non-square pixels then yes.

If you're going for PC/Mobile/Tablet then 768x576 square pixel 4:3 might be a better bet? (Or 788x576 if you are starting with a 720 source that has been scaled to 544 uncropped and is thus a little bit wider than the 702x576 4:3 area)

But then if you are going for PC/Mobile/Tablet you are probably better deinterlacing to 50p or 25p too - as many of these devices won't guarantee a decent deinterlace.

I forgot to mention the intended device is dvd/pvr box which is capable of playing mpeg2/4 h264 ts/mp4 files, so ideally as close or equal to broadcast format.

I’m not broadcasting anything just enjoying the experience in using ffmpeg

I’ll definitely give it a try noggin, many thanks for sharing the knowledge

If you're lucky you might be able just to remux it without re-encoding, setting the right aspect ratio (whatever that is).

You can use an MPEG2 patcher to alter the aspect ratio of 720x576 16:9 video that has been captured as 4:3 flagged 720x576, but I don't know if it will fix 544x576 16:9.

So if I have 1920x1080i 25 content and want to convert it to 1280x720 50 aka BBC iPlayer is it best to scale it first then deinterlace it, or do it in one go?

-vf 'w3fdif=complex:all,scale=1280:720' would probably do the job in ffmpeg for native 50Hz content (that does a deinterlace and then feeds that result of the deinterlace into the scale). There are more options for scaling - and you can always use YADIF if you prefer to deinterlace, or the new one that combines YADIF and Weston.