What to do with 1080i

[WildW]

Hi folks - newbie here looking for a little advice. What's the consensus on converting and compressing 1080i video?

I have 1080i video captured with Huffy in Virtualdub, and playback of it with VLC looks great, but obviously the file is huge. What would you guys recommend I do with it to get it to a sensible size h.264 file? (or anything else of reasonable size)

I've tried bob deinterlace followed by a resize down to 1280x720, but it looks a little blurry compared to just playing back the original 1080i so I'm wondering if I can do better. Am I right in thinking that keeping the video as 1080i will ruin any chances of it compressing nicely due to the interleaving?

[manono]

Am I right in thinking that keeping the video as 1080i will ruin any chances of it compressing nicely due to the interleaving?

You mean 'interlacing'. What kind of a video is it? Home video, a movie from television, what? Can you make a very short sample available? A simple bob deinterlace is guaranteed to produce poor results. Since it was capped in Huffy, you'll shrink it by maybe 80% (?) just reencoding for h.264.

[LigH.de]

IMHO, x264 is perfectly equipped for encoding 1080i video. It supports either MBAFF interlacing if the content might be combed (so it can decide whether to encode a slice = a – possibly small – video part in progressive or interlaced mode), or "fake interlacing" to satisfy Blu-ray compatibility if the whole content is in fact really progressive (1080 resolution on Blu-ray must be flagged as "encoded as interlaced", no matter if it is at all combed).

Always check if there is true interlacing by slowly watching a bobbed output field-by-field. No automatic detection can be certain about it.

Converting 1080i to double frame rate 720p is quite common as well, though. QTGMC can do that in a rather high quality in one call, I believe...

[WildW]

This is for captured TV. Stepping frame-by-frame it doesn't look combed, so perhaps I don't understand interlacing as well as I thought I did, or maybe my eyes can't see it at 1080.

I was not aware that any codecs handled interlacing nicely so I'm tempted to look at converting straight to x264 (I'll just throw it into Handbrake and see what happens.) Must admit the last time I captured any video we were all using xvid and it didn't take kindly to interlaced sources.

[LigH.de]

Stepping frame-by-frame it doesn't look combed

Maybe you did not do as intended...

I did not mean to check the original video frame-by-frame, that is unreliable.

I suggested to check the bobbed result field-by-field (means, apply a Bob() filter), in a scene with a steady motion or pan, and count almost equal fields. Steady motion = pure interlacing; forth-back motion = wrong field dominance (TFF/BFF); always double fields = progressive frames; double and triple fields alternating = Telecine (very rare with HD video, I hope); visible blends ... advanced repair.

[manono]

Stepping frame-by-frame it doesn't look combed...

If that's true - progressive content encoded as interlaced - then you have nothing to worry about and you shouldn't deinterlace it. You could run it through Handbrake or some other x264 encoder and do a 1-pass CRF encode for 20 or thereabouts and see if the final size is okay for you.

LigH.de's suggestion is a good one - bobbing it and then checking for pairs of frames the same or every frame different. One reason for doing it that way is because sometimes the player being used will deinterlace it by default and you can't be sure there's no interlacing present. However, since you said it's from a television capture I'm inclined to agree the content isn't interlaced. But that by itself is no guarantee.