Detecting interlaced DVDs :?:

Xcapee · Post by **Xcapee** » Thu May 17, 2007 11:14 am

Hi all.

Most DVDs are non-interlaced, so I haven't really bothered checking each one first because I am batch ripping all my DVDs to a directory on my NAS, and then each of the five computers in my house runs a loop which looks for a completed rip, claims a directory to encode and crunches away.

Every now and then, I end up with a DVD that I realise after the encoding was interlaced.

So my question is simply: How do I automatically detect if a DVD has interlaced video? Surely the VOB structure must tell the decoding player if the video is interlaced or not.

This raises the obvious question / feature request of an "automatic deinterlace" flag for the CLI and check box for the GUI. Failing that, any command line tool that can simply tell me if the video is interlaced or not so I can supply the right flag to the command line would be extremely helpful. I had hoped mplayer might fit the bill, but haven't managed to get it to (so far - I haven't fully read the docs yet).

rhester · Post by **rhester** » Thu May 17, 2007 4:23 pm

There is absolutely no programmatic way to correctly detect this. (More correctly, it is all but impossible to programmatically distinguish between interlaced, progressive, and hard telecined at 29.97fps.)

Good reading on this can be found at http://www.mplayerhq.hu/DOCS/HTML-singl ... t-telecine

Rodney

Cavalicious · Post by **Cavalicious** » Wed May 23, 2007 9:23 pm

Um...you two lost me here.

ALL DVDs (per format spec) are interlaced. Hence ALL DVDs are 480i.

You two talking about something else?

rhester · Post by **rhester** » Wed May 23, 2007 10:29 pm

My Sony DVD player looks fabulous when outputting pure progressive 480p from LOTR1. Analysis of the title with mplayer demonstrates quite clearly that it is anamorphic progressive 23.976fps content.

Rodney

Cavalicious · Post by **Cavalicious** » Wed May 23, 2007 11:51 pm

rhester wrote:My Sony DVD player looks fabulous when outputting pure progressive 480p from LOTR1. Analysis of the title with mplayer demonstrates quite clearly that it is anamorphic progressive 23.976fps content.

Rodney

I promise you, all DVDs are mastered in 480i. Progressive capable DVD players upconvert. Hell, My Samsung upconverts to 480p, 720p or 1080i.

The other misunderstood thing is the fact that ALL Bluray and HD DVDs are mastered in 1080i not 1080p. This was a HUGH debate at other forums, till someone had to bust out the spec.

tubbyman · Post by **tubbyman** » Thu May 24, 2007 2:31 am

I looked into this, as well. All DVDs are interlaced, but the frame reassembly instructions that accompany the frames may result in a progressive frame on your playback device. The reassembly instructions have a nasty habit of changing a lot, mid-stream, which makes detecting how to reassemble them that much harder.

I stopped working on this after spending a day or two working on porting the "transcode" library to osx, and just decided to set aside all of my VIDEO_TS folders that result in interlaced video and wait until I could find (or finish) an osx port of transcode. After all, the reason that I decided to use handbrake was so that I wouldn't have to write my own stuff.

Having said all of that, if you have a linux box around, the transcode/mencoder combo on linux provides some pretty nice deinterlacing algorithms.