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Discussion Starter · #1 ·
Philly PBS affiliate WHYY has three subchannels, 12.1 at 1080i and 12.2 and 12.3 at 480i. Last week there were some aspect ratio problems on 12.1 such as showing News Hour (HD) in postage stamp format (gray bars all four sides) which as of last night seem to have been fixed.


On their two 480i subchannels, though, lots of programs such as Living with Chernobyl, The Narcotic Farm, Tavis Smiley, Prairie Churches, and Brule Live are being shown postage stamp. The issue is picture quality, plus the inconvenience of forcing viewers to use the zoom functions on their TV's or converter boxes to get rid of the extra bars.


Engineers at WHYY and PBS are apparently working on implementing AFD (automatic format descriptor) coding to address the postage stamp issue. What I'm wondering is, is there some sort of work around that the local station can implement (until they get the AFD solution up and running) at the station's ATSC encoder? Is it possible, for example, to force or override some aspect ratio flag in PSIP at the individual program level (depending on the format of that individual program) to get rid of the extra bars, so that for example 16X9 content would display full screen on 16X9 TV's and letterboxed on 4X3 TV's?


I'm hoping there are some ATSC experts lurking here than can answer this.
 

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Quote:
Originally Posted by otaguy /forum/post/15543006


Philly PBS affiliate WHYY has three subchannels, 12.1 at 1080i and 12.2 and 12.3 at 480i. Last week there were some aspect ratio problems on 12.1 such as showing News Hour (HD) in postage stamp format (gray bars all four sides) which as of last night seem to have been fixed.


On their two 480i subchannels, though, lots of programs such as Living with Chernobyl, The Narcotic Farm, Tavis Smiley, Prairie Churches, and Brule Live are being shown postage stamp. The issue is picture quality, plus the inconvenience of forcing viewers to use the zoom functions on their TV's or converter boxes to get rid of the extra bars.


Engineers at WHYY and PBS are apparently working on implementing AFD (automatic format descriptor) coding to address the postage stamp issue. What I'm wondering is, is there some sort of work around that the local station can implement (until they get the AFD solution up and running) at the station's ATSC encoder? Is it possible, for example, to force or override some aspect ratio flag in PSIP at the individual program level (depending on the format of that individual program) to get rid of the extra bars, so that for example 16X9 content would display full screen on 16X9 TV's and letterboxed on 4X3 TV's?


I'm hoping there are some ATSC experts lurking here than can answer this.

A station can't not transmit BOTH 16:9 and 4:3 at the same time in the same stream. Either AFD has to be engaged or the viewers will have to interceed.
 

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Quote:
Originally Posted by otaguy /forum/post/15543006


Philly PBS affiliate WHYY has three subchannels, 12.1 at 1080i and 12.2 and 12.3 at 480i. Last week there were some aspect ratio problems on 12.1 such as showing News Hour (HD) in postage stamp format (gray bars all four sides) which as of last night seem to have been fixed.


On their two 480i subchannels, though, lots of programs such as Living with Chernobyl, The Narcotic Farm, Tavis Smiley, Prairie Churches, and Brule Live are being shown postage stamp. The issue is picture quality, plus the inconvenience of forcing viewers to use the zoom functions on their TV's or converter boxes to get rid of the extra bars.


Engineers at WHYY and PBS are apparently working on implementing AFD (automatic format descriptor) coding to address the postage stamp issue. What I'm wondering is, is there some sort of work around that the local station can implement (until they get the AFD solution up and running) at the station's ATSC encoder? Is it possible, for example, to force or override some aspect ratio flag in PSIP at the individual program level (depending on the format of that individual program) to get rid of the extra bars, so that for example 16X9 content would display full screen on 16X9 TV's and letterboxed on 4X3 TV's?


I'm hoping there are some ATSC experts lurking here than can answer this.

If the channel is HD then AIUI there is no other solution. HD 1080i and 720p broadcasts have to be in 16:9 raster format and thus 4:3 content pillarboxed (or worse - stretched) - though with an AFD compliant chain 4:3 receivers / displays can be told about the pillarboxing (i.e. the Active Format is 4:3) and zoom in if required.


HOWEVER - if the channel is SD, then there are two options I believe - and in the UK both are used.


1. AFD - just as above and with HD

2. MPEG2 header switching. This is where the encoder and broadcast chain passes 4:3 straight through and flagged as 4:3 full width, full height (not an option in HD as there is no 4:3 full height full width HD format standard in ATSC) and 16:9 passed straight through and flagged as 16:9 full height. This doesn't require AFD support BUT has the downside that the MPEG2 header can only change on an I-frame boundary, meaning the aspect ratio can't be changed frame accurately, so you get nasty stretched/squashed video on some transitions.


(In some broadcast environments 1. is used internally but to implement 2. externally - by having an AFD driven aspect ratio converter and MPEG2 encoder)


However - this can only work on SD broadcasts - and requires just as much engineering as an AFD system...
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by foxeng /forum/post/15543546


A station can't not transmit BOTH 16:9 and 4:3 at the same time in the same stream. Either AFD has to be engaged or the viewers will have to interceed.

So you're saying that the only solution to the postage stamp problem is AFD?
 

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Quote:
Originally Posted by otaguy /forum/post/15543803


So you're saying that the only solution to the postage stamp problem is AFD?

Either that or you manual adjust the aspect on your tv.
 

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Discussion Starter · #6 ·
Isn't this best addressed by the station rather than by the viewer? Doesn't PQ suffer if the broadcaster is filling only a portion of the available raster and the TV then takes this partial raster and magnifies it to fill the whole TV screen?
 

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Quote:
Originally Posted by otaguy /forum/post/15543803


So you're saying that the only solution to the postage stamp problem is AFD?

That is correct. And, each program has to have the AFD flag properly applied.

That would be not be a trivial undertaking.
 

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Quote:
Originally Posted by otaguy /forum/post/15543902


Isn't this best addressed by the station rather than by the viewer? Doesn't PQ suffer if the broadcaster is filling only a portion of the available raster and the TV then takes this partial raster and magnifies it to fill the whole TV screen?

No - for a couple of reasons.


1. Almost all 4:3 sources are SD (apart from the odd movie) - so they are lower resolution than the 1280x720 or 1920x1080 HD path they are being carried over (960x720 or 1440x1080 for the central 4:3)


2. Most 4:3 displays that are in use (with a few exceptions) are also SD.


So if you are taking a 4:3 SD source, upscaling it to 16:9 SD, and then downscaling it back to 4:3 SD then there shouldn't be a huge quality loss, and certainly less than the 540x360 resolution of the active bit of the postage stamped version in the 720x480 SD letterbox.
 

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Discussion Starter · #9 ·
Thanks, guys. It sounds like the consensus is sit tight and wait for implementation of AFD.
 

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OK, at the risk of being "outed", I can tell you that AFD is closer than you think. The folks with a major transmitter/encoder manufacturer provided a software patch on a previously obsolete piece of gear that will pass AFD to the stream, and allow a default setting on materials without an AFD flag. Combine that with upconverters that allow AFD insertion, and servers that pass existing AFD, allow over-riding the AFD if necessary, or allowing manually setting the AFD on a per server element basis allows controlling the downconversion format display actively on the CECB's in real time. The worst case I have seen is HD syndicated programs that have letterbox commercials in a 4x3 area within the HD feed. Short of clipping this out of the feed and changing the AFD for just that element, this is a worst case scenario. If the syndicators would only take it as seriously as the Peacock.


Also, after many searches on this board, I still cannot find a definitive list of CECB's that support AFD. I know by trial and error that the DTT901 and the Dish DTVPal operate differently in certain AFD modes.
 

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Quote:
Originally Posted by KE0MI /forum/post/15546479


Also, after many searches on this board, I still cannot find a definitive list of CECB's that support AFD. I know by trial and error that the DTT901 and the Dish DTVPal operate differently in certain AFD modes.

Interesting. Is this to do with what they do with 4:3 SD broadcasts containing 16:9 letterboxed (16L12) content (pillarbox to postage stamp - 16L12 in a 12P16 frame - or zoom to very soft full-screen 16:9 - 16F16 ?)


Here in the UK there was a mistake in the DTG specs for one specific AFD interpretation that got implemented by a large number of manufacturers ISTR...


That said - AFDs have been working really well in the UK for the last 9-10 years or so on our SD 16:9 outlets (The BBC broadcast them on digital OTA, and also use them to derive their digital satellite and analogue OTA feeds automatically.


The Sky DSat platform doesn't support AFDs - so the AFD internal feeds drive an ARC so that 12P16 content is ARCed to 12F12, and 16F16 is left as 16F16, and the ARCs embed a VBI signal that triggers the MPEG2 encoder to MPEG2 header switch from 12F12 to 16F16 dynamically.


Similarly the analogue transmitters take the AFD feed and create a 4:3 PAL encoded composite signal with the following options :


12P16 input 12F12 output

16F16 input shot 4:3 safe - 12F12 output

16F16 input shot 14:9 safe - 14L12 output

16F16 input shot 16:9 safe - 16L12 output


All handled automatically based on the AFDs in the metadata for the show when ingested or loaded into the playout system in London, Cardiff, Glasgow or Belfast. (The BBC has four playout centres for BBC One and Two - London is the network but the other three "Nations" also run parallel network operations with their own schedules and presentation/continuity operations)
 

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Quote:
Originally Posted by sneals2000 /forum/post/15550642


Interesting. Is this to do with what they do with 4:3 SD broadcasts containing 16:9 letterboxed (16L12) content.



Similarly the analogue transmitters take the AFD feed and create a 4:3 PAL encoded composite signal with the following options:


12P16 input 12F12 output

16F16 input shot 4:3 safe - 12F12 output

16F16 input shot 14:9 safe - 14L12 output

16F16 input shot 16:9 safe - 16L12 output

sneals2000 can you please define 12P16, 12F12, 14L12, 12F12, etc..? These terms I've not come across here in the US with manufactures of encoding equipment. Generally they use, Crop, Full, Center Cut, Letterbox, 4:3, 16:9, 14:9, etc.. US broadcasters are finally starting to use AFD, especially on NBC and FOX now. CBS has not yet, hell they don't even do Dolby Digital properly for affiliates, (it's there but they don't flag it so your 5.1 encoder knows when to pass, or generate 5.1 from stereo 2.0 on other programs they have, so we just take their 2.0 and generate a 5.1 mix all the time, doh..CBS used to do DD right with a flag, but dropped it at one point..)


PBS's are simply the worst over here; I've not yet seen one PBS actively do aspect ratio control properly. It seems their sources of program material is from all different production companies and producers. (They don't even try to fix it on the local level.) Not homogenized like the big four networks expect content to be delivered as.


I.e. CBS only accepts 16:9 1080i 60i HD content for their network programming. Plus they have recently switched over to 16:9 news delivery only, with pillar boxes on sides if it's 4:3.


But back to PBS, lots of their shows are from the BBC and those now look like they are shot in 16:9 HD. Yet they look like they are delivered as 4:3 with 14:9 anamorphic squeeze. So on a 4:3 TV it looks like a slight letter box, but with a stretch, and on their HD program feed a window box that almost reaches the left and right sides of the frame, but also with a strange stretch quality.. It's really irritating to look at. I've been told by PBS engineers this is an ongoing issue because of the varying sources of feeds. Some programs are independently produced from the CPB (Corporation for Public Broadcasting) and come down different satellite feeds, with little knowledge of what it's going to be ahead of time. While many feeds are automatically taken into a scheduling system, and the tuners and format converters can't be told from the scheduling software to change aspect ratio ahead of time. You can't ask the overnight engineer who's taking all these feeds to keep on switching aspect ratios on sat feeds, while they are running three program feeds, and taking five sat feeds for the next days programming, now that most stations have cut back the staff, and replaced them with automation equipment that supposed to do everything in the background. But now you have these problems arising.. Very frustrating to see it all the time when you rather not have to change aspect ratios and zoom settings on your TV..


And here's another one that's annoying. I love watching BBC America's Top Gear program. It always comes down as 16:9 SD window box in a 4:3 SD feed on Comcast cable, they don't have BBC America HD yet, and I suspect they never will. So I have to keep switching the settings to Zoom 1 on my Scientific Atlanta DVR that won't remember what setting I had on BBC America the last time I tuned it in. Simply the worst DVR ever conceived.


Anyway my rant is over. But it sounds like these problems are universal, until every one finally produces in HD.
 

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Quote:
Originally Posted by mdamberger /forum/post/19521729


...PBS's are simply the worst over here; I've not yet seen one PBS actively do aspect ratio control properly...

We have two OTA PBS sources; one from Arkansas and one from SW Missouri. The aspect ratio problems on the Missouri sub channels are far less frequent than the Arkansas. On the Arkansas sub channels, one never knows if a program is going to be watchable or not until it is on. And some of the distorted modes cannot be fixed by the viewer, depending on the setup.


This problem is ridiculous.
 

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With a Zenith 901, aspect ratio can't be changed unless a subchannel is HD. Unfortunately, I only know of one local subchannel that is HD (KGO 7-2). For PBS, this means that the rush to 16:9 graphics leaves plenty unavailable if viewing them on a PBS subchannel. Not good.
 

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Last night the engineer at KBFX FOX in Bakersfield must have pressed the wrong button a few times because parts of COPS and America's Most Wanted were shown in pillarboxed and letterboxed SD.
 

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Quote:
Originally Posted by KE0MI /forum/post/15546479


OK, at the risk of being "outed", I can tell you that AFD is closer than you think.

That varies from one network to another. For instance, CBS has no implementation of AFD.


Stations that purchase equipment to enable AFD may find that equipment obsolete when most TVs have 16X9 displays.
 

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My local PBS station - KQED in San Francisco still uses postage stamp broadcasting on both channels: 54 and 9 - for a total of 7 programs/subchannels.
Is there any hope ? :rolleyes:
 

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Quote:Originally Posted by sneals2000

Interesting. Is this to do with what they do with 4:3 SD broadcasts containing 16:9 letterboxed (16L12) content.


Similarly the analogue transmitters take the AFD feed and create a 4:3 PAL encoded composite signal with the following options:

12P16 input 12F12 output
16F16 input shot 4:3 safe - 12F12 output
16F16 input shot 14:9 safe - 14L12 output
16F16 input shot 16:9 safe - 16L12 output



sneals2000 can you please define 12P16, 12F12, 14L12, 12F12, etc..? These terms I've not come across here in the US with manufactures of encoding equipment. Generally they use, Crop, Full, Center Cut, Letterbox, 4:3, 16:9, 14:9, etc.. US broadcasters are finally starting to use AFD, especially on NBC and FOX now. CBS has not yet, hell they don't even do Dolby Digital properly for affiliates, (it's there but they don't flag it so your 5.1 encoder knows when to pass, or generate 5.1 from stereo 2.0 on other programs they have, so we just take their 2.0 and generate a 5.1 mix all the time, doh..CBS used to do DD right with a flag, but dropped it at one point..)
How rude. I didn't answer the question. Five years on - here goes!

First number defines the active picture area in XX:9 format (12 = 12:9 = 4:3, 16 = 16:9, 14 = 14:9)
Middle letter defines the presentation. P = Pillarbox (black bars either side), L = Letterbox (black bars top and bottom), F = Fullscreen (no black bars)
Second number define the total picture area in XX:0 format

So 12F12 = full-width, full-height 4:3 picture in a 4:3 raster. 12P16 = full height 4:3 picture pillar boxed into a 16:9 raster. 16L12 = full width 16:9 picture letterboxed into a 4:3 raster.

These modes are standard on all the European ARCs I've used, and are also used in the UK AFD spec. Here the AFD is used to signal both the active picture area AND the broadcaster suggested presentation mode on a non-native display.

For many years the BBC broadcast almost universally 16:9 SD content. This was always broadcast 16F16 on digital platforms, but on 4:3 platforms (and 4:3 displays connected to an AFD-compliant set-top box receiving the digital platforms) different shows would be output differently.

Sport was flagged for 12P16 output - so on analogue PAL transmissions and set-top boxes which were fully AFD-friendly, the content was displayed 12F12 (i.e. a centre-cut was used)
Almost everything else was flagged for 14L12 output, so on analogue PAL and with fully AFD set-top boxes feeding a 4:3 TV, the output was 14L12 (i.e. a small amount of left/right crop and thin black letterbox bars top and bottom)
Movies and some arts shows were flagged for 16L12 output, so on the analogue and fully AFD outputs for 4:3 TVs, the output was 16L12 (i.e. full-width 16:9 with large letterbox bars top and bottom)

All of the AFD settings are tied to the programme master tapes and integrated with the playout automation system that networks use.

In the UK 4 of the 5 main networks and their related networks - BBC One, BBC Two, ITV and Channel Four - are all played out by Ericsson - formerly Red Bee Media and Technicolor pre-acquisition by Ericsson. The networks don't run their own playout operations - so the systems used are pretty uniform.

Regional centres have been equipped with the required AFD/WSS ARCs etc. required to pass network shows and flag local shows correctly for around 15 years or so.
 
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