Aspect Ratios in Broadcasts and VideoReDo

Black Hole

May contain traces of nut
This might not be news to some, but I've been playing around with StDef BBC FOUR recordings and discovering stuff. In particular: broadcasts of old 4:3 material (Come Dancing), no doubt scraped up from some unearthed video tape.

The continuity announcements fill the 16:9 frame, then the programme material is not 4:3 but actually transmitted as 16:9 with the pillarbox bars included in the image. But, if set to "auto", the centre 4:3 stretches to fill the screen (short & fat), so there must be a flag which tells the display to over-scan.

The pixel format is 704 x 576 throughout, with a pixel aspect ratio 16:11 ( 16 x 704 : 11 x 576 = 11,264 : 6,336 = 16:9 ). When saved as a snapshot in VLC, the resulting .png ( 1:1 pixels ) is 1024 x 576 ( = 16:9 ) containing black sidebars 128 pixels wide each, so to display the video on a screen with square pixels, the 704 original pixels have to be resampled to make 1024 (or more likely 1920, with the 576 vertical pixels resampled to 1080).

Curiously, my version (5) of VideoReDo TV Suite does not interpret the aspect settings correctly and shows the 16:9 "outer frame" in a 4:3 envelope, thus displaying the original 4:3 "inner frame" as 1:1! This is what caused me considerable consternation until I could untangle where the fault is (VideoReDo!). The output of a save from VideoReDo plays correctly in VLC (and still does not display correctly when re-imported into VideoReDo).

I had intended that, for archival purposes, the video file would only contain 4:3 material – but that was when I expected the transmission was 4:3. Removing the side bars and outputting 4:3 will require re-encoding, and I presume the sidebars themselves don't contribute much to the size of the file, so they'll just have to stay.

Is it the case that all broadcasts of 4:3 material include the sidebars in an overall 16:9, and just signal the display (TV) to zoom in with a flag?
 
This is a bit like Talking Pictures TV who said on their website (as an answer to an FAQ) that all films are broadcast in the original format. They used to broadcast 4:3 material as 4:3 with the flag (I forget it's name) set to pillar box on wide-screen TV and behave properly on old 4:3 TVs. A lot of the time they still do. But the Rupert Davies series of Maigret - definitely 4:3 originally - has been broadcast in 16:9 with the black bars embedded.
As far as I can tell some 4:3 material still does fill the space and isn't broadcast with sidebars. When I Videoredo some old 4:3 films there is no evidence of black bars in the .TS file (I wanted lower case TS but autocorrect won't let me), nor if I use another editor or play in VLC or some other out of date media player.
The whole thing is a mess. You only have to surf the channels to find a 4:3 programme expanded out to 16:9. Alternatively ITV now crops The Sweeney and others to be 16:9, with people's heads lost off the top of the screen!
I'd prefer to archive 4:3 as, er, 4:3, but it's such a pain to crop and re-encode that I just archive as is.
 
In which case there is an open question how it works. I suppose there must be information that the data is 16:9 with 4:3 content, and another means to flag that the data is 4:3.
 
You're at the mercy of the broadcasters. Really it is impossible to predict what you are going to get, apart from with the main players (and even they can get it wrong sometimes). The crappier a channel is, the more the picture gets mangled.
Thankfully all this crap went away with the HD services. Everything is 16:9 and there is no aspect ratio signalling. You just get it pillar-boxed with 4:3 material.
 
Thankfully all this crap went away with the HD services. Everything is 16:9 and there is no aspect ratio signalling. You just get it pillar-boxed with 4:3 material.
As I normally record StdDef I hadn't noticed that. (Trying to process HiDef material, assuming I've recorded it on the right Humax (2000T not 5000T), is a pain on my underpowered laptop.
I'll have to do a test on some old 4:3 rubbish on BBC FOUR just to see.
 
In which case there is an open question how it works. I suppose there must be information that the data is 16:9 with 4:3 content, and another means to flag that the data is 4:3.
Isn't that what AFD (https://en.m.wikipedia.org/wiki/Active_Format_Description ) does? Or am I missing something here? I did think you were referring to StdDef recordings - because I thought you once said that's what you used. Possibly I misremembered or you have changed your recording habits.
 
I did think you were referring to StdDef recordings - because I thought you once said that's what you used. Possibly I misremembered or you have changed your recording habits.
Yes, I'm talking StDef, and that is my default. I don't see much point recording a HiDef version of a (less than) 625-line original, even if I did routinely use HiDef!
I've been playing around with StDef BBC FOUR recordings

Isn't that what AFD (https://en.m.wikipedia.org/wiki/Active_Format_Description ) does? Or am I missing something here?
Interesting read. I realised there had to be something doing that job, I just didn't know what. It seems to me VideoReDo is not interpreting the AFD correctly, but preserves it when saving (I presume as a consequence of saving the video stream as-is). I wonder what would happen if it had to re-encode?

I suspect VLC isn't responding to AFD at all, and just presenting the data aspect ratio.

Thankfully all this crap went away with the HD services. Everything is 16:9 and there is no aspect ratio signalling.
Useful to know, but I don't see that as a benefit. It makes life easier for the display maybe, but it is less efficient to include black areas in the transmitted data, and less desirable for (unapproved) recording and subsequent use. It would be better if the broadcasters simply got it right, and the AFD article says the UK invented it and got an Emmy for it, and it's in the D-Book.

Is there really no aspect ratio signalling on HiDef? How does a TV know when to expand the centre section if not (maybe it doesn't)? I'll find out on Sunday.
 
I don't think any of my video editors obey the AFD as such. VideoRedo plays games with me. (Remembering that I record everything with padding). It takes the aspect ratio of the first frames. So with TPTV if the recording starts at the end of a 4:3 film, the ads will look compressed horizontally. If it starts in 16:9, a 4:3 film will look stretched. After I've edited the programme it may look in the wrong aspect ratio in the editor. I think if I just write to mpg with intelligent recoding it usually comes out okay. However, I always use a template which sets the correct aspect ratio in the mpg file. Works well with mpeg. When TPTV was on a DVB-T2 mux I used to have real problems editing out the ads. It used to jump in and out of wide-screen at the edit points whatever I did. Eventually I found an advanced setting that solved the problem. Not needed anymore as Forces TV no longer exist and TPTV is on a DVB-T mux.
 
Of course, it could be easy to tell if the broadcast of a 4:3 programme is in 4:3 or 16:9 with pillarbox.
Penny Paradise.jpgSeven Days to Noon.jpg
The DOG is a giveaway!
 
The DOG is a giveaway!
Not for Come Dancing: the BBC FOUR ident is within the 4:3 (which is within a 16:9).

It takes the aspect ratio of the first frames.
Hmm. I wish it did! When I had the 16:9 continuity on the front, VRD displayed that as 4:3 and then the 4:3 content as 1:1. So I used nicesplice to crop the continuity, and VRD still displayed the 4:3 content as 1:1.
 
Hmm. I wish it did! When I had the 16:9 continuity on the front, VRD displayed that as 4:3 and then the 4:3 content as 1:1. So I used nicesplice to crop the continuity, and VRD still displayed the 4:3 content as 1:1.
I think I'm using a fairly old VideoRedo. Perhaps the first that properly implemented H264. (Don't have acces to the laptop at the moment to find the actual build number).
You say it is displayed (in the editor?) wrongly. What happens when you save the edit? Have you tried forcing 16:9 from the advanced settings? When I've edited your traditional DVB-T broadcasts to mpg files using VRD I've been able to set the aspect ratio I want (well, 4:3 or 16:9 definitely) for the whole programme. If your content is displayed in VRD as 1:1 but you save as 16:9 you ought to get a 4:3 with pillarbox. (When played in your favourite media player, or back on a Humax).
Not for Come Dancing: the BBC FOUR ident is within the 4:3 (which is within a 16:9).
I suspected it might be. Too complicated for TPTV!
 
What happens when you save the edit?
It plays fine when saved and played in VLC (and elsewhere), it's just disconcerting that VRD doesn't display it properly in the editor. Like I said above, I don't know what would happen if I asked VRD to do a full re-encode.
 
It plays fine when saved and played in VLC (and elsewhere), it's just disconcerting that VRD doesn't display it properly in the editor. Like I said above, I don't know what would happen if I asked VRD to do a full re-encode.
It is a bit disconcerting. A number of times I've had to play the original .ts to work out the correct aspect ratio. I can't remember finding a setting adjustment for the editor display. I'm used to it now, but it is a pain!
Note that VRD allows copying of frames whilst changing just the aspect ratio - so, like I said previously, I now always set the output to the aspect ratio I want knowing that will not slow the saving process down (well, perhaps changing one byte in a frame but not recoding). It also ensures on real 4:3 programmes that a rogue 16:9 frame around a break doesn't creep in. If you really need to do a full re-encode I would encourage you to  set the required aspect ratio and not let VRD guess. (It would probably guess correctly, but why take the risk?)
 
Scrub that. I found how to adjust the display in my version of VRD (5.1.1.179 2014). Whether it is the same for your version, who knows?
Tools/Options/Playback Devices - Displayed Aspect Ratio. Defaults to auto. I've now set mine to 16:9 which might make things easier, although I may get a lot of old films where people look like the doctor in ST:Voyager in an early episode where he was short, fat and stood on his chair!
 
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