Different DAR between Mediainfo and DGIndex

[tppytel]

This is hardly a critical problem, but I'm curious about what's happening behind the scenes. I'm reencoding the "Making of Amadeus" video from the BD into H.264 because the original is a VC1 encode that my Plex server would otherwise have to transcode. As often happens with special features, it's an odd file - looks like it was originally mastered for DVD, but was given a quick reencode and deinterlacing for the BD release. It's NTSC rate, but progressive, with a coded resolution of 720x480. Mediainfo reports "Display Aspect Ratio: 3:2" and "Original Display Aspect Ratio: 16:9". However, when I index the stream with DGIndexNV, it reports "DAR 20:11". I'm curious about where those 16:9 and 20:11 ratios are coming from in the file and which one would be more correct when determining a SAR for reencoding.

A 10 second clip is attached. Thanks for any insights you can provide.

[poisondeathray]

16:9 NTSC SD BD SAR is always 40:33 it's the only legal value. BD uses ITU aspect ratios , so "16:9" is actually a bit wider than 16:9 . Instead of 1.7778 its 1.8181

20/11 comes from the calculated DAR
20/11 = 720/480 * 40/33

[tppytel]

Hmm... OK. I've never completely understood ITU aspect ratios. Is it right to say that they're basically just implementation standards derived from old broadcast technology limitations? In this case, where I'm just going to be playing back off of a Plex server, would it be more correct to use a 32:27 SAR to get a true 16:9 DAR?

[poisondeathray]

Hmm... OK. I've never completely understood ITU aspect ratios. Is it right to say that they're basically just implementation standards derived from old broadcast technology limitations? In this case, where I'm just going to be playing back off of a Plex server, would it be more correct to use a 32:27 SAR to get a true 16:9 DAR?

Yes, it ' s basically one set of interpretation rules.

You can argue which one is "correct"; but "16:9" NTSC SD BD , without a doubt uses 40:33 (which is ITU) . That is the only valid value. NO other choice

It should also be noted that it might have the wrong content AR from the transfer process . Just because the SAR is 40:33 , doesn't necessarily mean the prior steps were done correctly - somewhere along the way there might have been errors, e.g. maybe the master was incorrectly done, or DVD botched etc...

The difference in AR is small, and most people won't notice, but if you wanted to be "perfect" you would find a reference object, like a circular clock , or car tire shot straight on and determine which SAR looks correct then use that one. If a "circle" looks "oval" it's the wrong content AR. The perfect value might even be something entirely different due to accumulated prior mistakes

[Bernix]

Hi,
according to IMDB it should be 4:3.
what does this mean in media info ?

Scan type : Progressive
Scan order : Bottom Field First

This is what potplayer said.

[Attachment 43247 - Click to enlarge]

[tppytel]

I don't know where IMDB got that - it's clearly squashed at 4:3. It's definitely meant to be some kind of widescreen. Perhaps there was some 4:3 VHS release of it at some point and IMDB got the ratio from there?

And yeah... that Progressive + Bottom Field First readout is really weird too, isn't it? I'm guessing the original DVD version was deinterlaced for the BD release, but that somehow that BFF tag was left intact. The video is clearly Progressive when viewed frame by frame in VirtualDub. But SD special features from BD's are often very strange. I'm guessing it's just not cost-effective to properly retransfer/remaster old DVD material, so they just take the old file or a digital intermediary, do a quick and dirty reencode, and throw it on there figuring that few people will ever notice. And that's probably reasonable.

I think I'm just going to reencode this one with a 32:27 SAR and call it a day. Thanks for the help.

[poisondeathray]

And yeah... that Progressive + Bottom Field First readout is really weird too, isn't it? I'm guessing the original DVD version was deinterlaced for the BD release, but that somehow that BFF tag was left intact. The video is clearly Progressive when viewed frame by frame in VirtualDub. But SD special features from BD's are often very strange. I'm guessing it's just not cost-effective to properly retransfer/remaster old DVD material, so they just take the old file or a digital intermediary, do a quick and dirty reencode, and throw it on there figuring that few people will ever notice. And that's probably reasonable.

This is a BD rule too - native progressive isn't allowed for primary SD stream . So content can be progressive, but it has to be encoded or flagged interlaced

[Bernix]

They are almost correct in everything.
http://www.imdb.com/title/tt0339339/technical?ref_=tt_dt_spec
And your video (that you posted) is almost 4:3 (1,33333)

Bernix

[tppytel]

The clip I posted may look OK in 4:3, but scenes from the rest of the vid are very obviously wrong in 4:3. Faces are clearly squashed. No way is it 4:3.