Greg Giczi, General Manager of KAET (Phoenix PBS) posted a message on a local Phoenix forum stating that the station is changing formats on Oct. 30th. This is being done to allow KAET to add an additional sub-channel. We currently have one video sub-channel and one audio sub-channel.

Giczi says "We anticipate that you will see little difference in picture quality with this format change. We are using the latest and best converstion and statistical multiplexing equipment to make the digital bandwidth as efficient as possible."

Any other PBS stations down rezing the picture? If this won't affect the picture quality, why did PBS select 1080i in the first place?

Greg Giczi, General Manager of KAET (Phoenix PBS) posted a message on a local Phoenix forum stating that the station is changing formats on Oct. 30th. This is being done to allow KAET to add an additional sub-channel. We currently have one video sub-channel and one audio sub-channel.
I have heard of other PBS stations doing this as well when they are adding sub channels. Which stations those are I do not recall right now.


Any other PBS stations down rezing the picture? If this won't affect the picture quality, why did PBS select 1080i in the first place?

Technically its not down-rezzing, but cross conversion.

Greg Giczi, General Manager of KAET (Phoenix PBS) posted a message on a local Phoenix forum stating that the station is changing formats on Oct. 30th. This is being done to allow KAET to add an additional sub-channel. We currently have one video sub-channel and one audio sub-channel.

Giczi says "We anticipate that you will see little difference in picture quality with this format change. We are using the latest and best converstion and statistical multiplexing equipment to make the digital bandwidth as efficient as possible."

Any other PBS stations down rezing the picture? If this won't affect the picture quality, why did PBS select 1080i in the first place?

I guess the idea is that 720p won't be affected nearly as much as 1080i with a subchannel. In other words, you'd notice the difference in bandwidth loss on a 1080i signal while you might not with the 720p feed.

I believe that my local PBS, WKAR, does the cross conversion and transmits at 720p. There are no noticeable issues with the PQ.

PBS in Seattle switched to 720p at least a year ago. The switch was not to add subchannels but to allow the HD version of the 5 subchannels to show a picture without breaking up horrendously when movement was involved. The switch to 720P in Seattle's PBS case was a huge improvement. But 5 channels is just a fricken joke....at least the change did help a lot...Apparently the word got out to other PBS cities...

Keith

KCET (which I get here in Santa Barbara through Cox) also does 720p. I believe they have subchannels, but we don't get any. They also use a significantly lower bitrate on it (watching it now, it never went above 11 Mb, and was typically much lower). I haven't watched anything high motion yet, but Frontline and The War both look great.

WKNO in Memphis is side converting to 720p. I noticed an immediate lack of depth and some lack of detail.

I haven't watched anything high motion yet, but Frontline and The War both look great.
Yeah, those motion-control shots of photos would look great as....well...still images. Luckily, PBS isn't the "shakey-cam" network...

KNME (Albuquerque) went from 1080i to 720p and now is back to 1080i. There are 2 sub-channels (PBS-SD, and V-me a spanish language channel).

Pic quality was pretty poor when it was 720p. Its better now but bit-starved.

Any other PBS stations down rezing the picture? If this won't affect the picture quality, why did PBS select 1080i in the first place?In Indy they switched from 1080i to 720p a long time ago. They felt the image looked better with what bandwidth they had left after adding too many subchannels to count.

KET is the state-run network of PBS stations in Kentucky, and all of them are identical as far as I know. They run I believe 6 SD channels during the day and 1 720p HD and 2 SD subs during primetime. KET 4 (the -4 subchannel) actually switches from the 480i format to 720p right at (I believe) 7pm, and all but two of the other SD subs are dropped.

Comparing the quality of WCVN (Covington, KY) and WCET (Cincinnati, OH) which runs one 1080i HD channel and 1 SD sub, and additionally an unknown datastream, You can see a difference. The KET 720p channel is for the most part artifact/macroblock free, but has slightly less detail. The 1080i channel from WCET has some noticeable macroblocking but does show more detail when there isn't much motion.

But 5 channels is just a fricken joke
I saw a post on Sat Guys where some PBS station had like 7 subs, and 3 of them were the radar with different music. No HD station.

Makes you not want to contribute.

I guess the idea is that 720p won't be affected nearly as much as 1080i with a subchannel. In other words, you'd notice the difference in bandwidth loss on a 1080i signal while you might not with the 720p feed.

In KAET's case, I think it's more of "Our PQ is already so bad that you won't notice a difference.

KAET has tons of blocking artifacts right now (at 1080i with an SD and a classical music substation). Every jump cut and any significant motion causes gobs of blocking.

I saw a post on Sat Guys where some PBS station had like 7 subs, and 3 of them were the radar with different music. No HD station.

Makes you not want to contribute.

Assuming this isn't a joke (!) Were they really three separate identical video streams? It is perfectly possible to create three "virtual channels" mapping a single video stream to the three separate channels, but with three different audio streams AIUI. You'd need to do a decent demux and list the PIDs of the various services. (TSReader is your friend for this)

Assuming this isn't a joke (!) Were they really three separate identical video streams? It is perfectly possible to create three "virtual channels" mapping a single video stream to the three separate channels, but with three different audio streams AIUI. You'd need to do a decent demux and list the PIDs of the various services. (TSReader is your friend for this)
They were different streams, each one had it's own channel number. I was just browsing their site after a new post came on the 1 thread I'm subbed to over there. Let me do some more researching and I'll see if I can find it.

Edit: sorry, I was wrong. It's 8. Post #7, http://www.satelliteguys.us/directv-hd-discussions/109087-your-locals-has-worst-hd-pq.html

4 sub channels is nothing. Our local PBS affiliate has 8 sub channels. Here is how they broadcast:

WMVS:
10-1: MPTV World
10-2: MPTV V-Me (Spanish)
10-3: MPTV Kids
10-4: MPTV Create
10-5: NWS Radar with classical music
10-6: NWS Radar with NOAA Weather Radio KEC60
10-7: NWS Radar with NPR
10-8: NWS Radar with smooth jazz music

36-1: Broadcast on a limited schedule programming in HD from Analog 10.

I think this stations "wins".

720p uses ~12% less bandwidth than 1080i.

They were different streams, each one had it's own channel number. I was just browsing their site after a new post came on the 1 thread I'm subbed to over there. Let me do some more researching and I'll see if I can find it.

Edit: sorry, I was wrong. It's 8. Post #7, http://www.satelliteguys.us/directv-hd-discussions/109087-your-locals-has-worst-hd-pq.html



I think this stations "wins".

I would have to believe all the radar channels are using the same video stream and just different audio. I do believe you can have multiple channel numbers point to the same video.

I would have to believe all the radar channels are using the same video stream and just different audio. I do believe you can have multiple channel numbers point to the same video.

Correct. We do that to make an HD SAP/DVS channel. It's not hard to do and is done in the multiplexer
and declared in the VCT via PSIP.
A virtual channel is created with a new program number using existing pids. For example: (all hex)

18-1 Pgm 3 PMT=30, Vpid/PCR=31, A1=34,A2=35,A3=36
18-2 Pgm 4 PMT=40, Vpid/PCR=31, A2=35
18-3 Pgm 5 PMT-50, Vpid/PCR=51, A1=54,A2=55,A3=56

They were different streams, each one had it's own channel number. I was just browsing their site after a new post came on the 1 thread I'm subbed to over there. Let me do some more researching and I'll see if I can find it.

You can have multiple channels point to the same video, KTLA runs 5.1 HD in English and 5.3 HD in Spanish. The video for both channels is the same video but the audio stream is different.

In KAET's case, I think it's more of "Our PQ is already so bad that you won't notice a difference.

That is what I thought when I read it. They have said they use some sort of filter ("rolls off high frequencies") that reduces the bandwidth of the satellite feed without re-compressing. I think this device is what causes all the weird static I see on this channel.

I met my learned new things quota for the day.

PBS is split up 4 ways here in Chicago, they had to downrezz to keep the bandwidth in order.

They were different streams, each one had it's own channel number.



A different channel number seen by the end-user doesn't mean a different or unique video stream.

It is perfectly possible to set up different channels that point to the same video stream, but different audio streams. That is one of the joys of modern technology - channel numbers are just convenient ways of grouping streams together for the end user. You configure the multiplexer to map different video and audio streams(each stream has a unique PID) to different "channels".

To confirm what is really happening you either need to know how the broadcaster has set-up their multiplexer, or you need to analyse the ATSC transport stream using something like TSReader - which will list all of the PIDs being broadcast, their data rates, and what services they are mapped to.

That is what I thought when I read it. They have said they use some sort of filter ("rolls off high frequencies") that reduces the bandwidth of the satellite feed without re-compressing. I think this device is what causes all the weird static I see on this channel.

AIUI there are a number of devices using techniques that can reduce the data rate of an MPEG2 stream without decoding it and recoding it - though the quality of them is not universally praised. (They don't introduce concatenation artefacts, but also can be cruder in how they throw away information)

PBS is split up 4 ways here in Chicago, they had to downrezz to keep the bandwidth in order.

Although I noticed that 11-4 was gone last Sunday. I'll have to check to see if that was temporary.

WWTW-V, which occupies 11-4 on my TV, was there today. Spanish speaking channel.

Yeah-- I didn't think that WTTW would take it off permanently.

To the OP -

If it's anything like here in Chicago, believe me, it'll be the beginning of the end.

This is being done to allow KAET to add an additional sub-channel. We currently have one video sub-channel and one audio sub-channel.
What sub-channel are they adding?

What sub-channel are they adding?

As of this evening (Oct 31), KAET-DT consists of:
8.1 KAET-HD
8.2 Create
8.3 World <-- The new sub-channel added today
8.4 KBAQ

I am seeing very strange things with 8.1 on my various digital tuners (Mitsubishi integrated, LG integrated, & Fusion 5 Lite PC tuner card).
TSReader is reporting that 8.1 video resolution is 960 x 720i (instead of 1280 x 720p). I guess that would be 720p's version of HD-Lite, eh?
The integrated tuners in my HDTV's do not handle that resolution very well, but my PC tuner card is happy with it.

Even better is that it's 960x720i at 59.94 frames per second, not 29.97 like one would expect for an interlaced broadcast. The best laid plans of mice and men...

720i doesn't exist as a broadcast format - that may be a bug in the otherwise excellent TSReader. The 59.94 frequency kind of confirms that it is really 720p I think?

960x720/60p IS a possible format - though I didn't think it was a valid OTA standard (it isn't in the ATSC grid of resolutions - though this ended up not being a mandatory requirement ISTR?) - though it is perfectly OK for satellite where proprietary boxes are used (and cable?)

For info DVCProHD - one of the lower cost broadcast HD formats - in 60Hz mode uses 960x720/60p on-tape (and 1280x1080/60i)...

Has anyone taken a look at the resolution their PBS stations are sending SD in? I noticed that mine is saving bandwidth by using a resolution that's not in the ATSC table, something like 528x480. Are they breaking the law when they do this?

Interesting.

In the UK - where we use DVB not ATSC - we have a slightly larger group of accepted resolutions.

On Freeview OTA we have a mandate that the main OTA analogue services simulcasts have to be broadcast at full SD resolution (which is 704x576 or 720x576 - either can be used to carry a 702x576 analogue equivalent signal) However some services are allowed to broadcast 4:3 SD in a pillarbox - effectively a 544x576 active portion in a 704x576 or 720x576 frame.

However for the non-analogue OTA services 544x576 can be used - and is by some broadcasters - for both 4:3 and 16:9 services - and on satellite in extreme cases this can be used to carry 4:3 pillarbox in a 16:9 frame - leaving you with around 400x576 resolution active pictures...

Similarly the DVB HD specs also include the option of 1440x1080 as well as 1920x1080 - so either of these can be used.

My understanding of the US ATSC "standard" is that the final version DIDN'T include a mandate to use one of the 18 resolutions/frame rates - so "non-standard" resolutions may not be illegal.

My understanding of the US ATSC "standard" is that the final version DIDN'T include a mandate to use one of the 18 resolutions/frame rates - so "non-standard" resolutions may not be illegal.

That would sort of make them "suggested" resolutions. I got the impression this table was some kind of law from all the people complaining about D* giving them "HD-Lite" because 1280x1080 isn't in the ATSC table. Yes, ATSC wasn't exactly relevant for satellite but here I'm seeing a resolution in a real terrestrial ATSC stream that is definitely not in the ATSC table.

Therefore I will call it...SD-Lite. :)

720i doesn't exist as a broadcast format - that may be a bug in the otherwise excellent TSReader. The 59.94 frequency kind of confirms that it is really 720p I think?

960x720/60p IS a possible format - though I didn't think it was a valid OTA standard (it isn't in the ATSC grid of resolutions - though this ended up not being a mandatory requirement ISTR?) - though it is perfectly OK for satellite where proprietary boxes are used (and cable?)

For info DVCProHD - one of the lower cost broadcast HD formats - in 60Hz mode uses 960x720/60p on-tape (and 1280x1080/60i)...No, it really was 960x720i at 59.94 frames per second, as reported by any number of different tools. Of course, there was no interlacing or combing present because it was being fed progressive frames, though that doesn't change the information in the stream or how decoders attempt to deinterlace it. As of this morning, they're running at 1280x720i at 59.94 frames per second. It would appear that the engineer just needs to go in and flip the encoder out of interlaced mode and into progressive. The resolutions table was never adopted so stations are free to run at whatever they want. The CBS affiliate here was running at 1280x1080i for a few days before CBS corporate found out and made a couple nasty phone calls and ended that practice (or so the story goes).
Has anyone taken a look at the resolution their PBS stations are sending SD in? I noticed that mine is saving bandwidth by using a resolution that's not in the ATSC table, something like 528x480. Are they breaking the law when they do this?All the SD subchannels in Phoenix are running at 704x480i except for Create on PBS which is running at an oddball 720x480i. The station's engineer claims they are simply rate shaping the satellite feed, though I don't have any way to confirm the original resolution since I don't have an FTA dish. There's nothing illegal about 528x480i, and I think most of us would prefer to see Weather- and all that type of crap running down there with the saved bits going back to the HD channel. I have made the suggestion a few times to the NBC and CBS affiliates here, but they never respond.

....

My understanding of the US ATSC "standard" is that the final version DIDN'T include a mandate to use one of the 18 resolutions/frame rates - so "non-standard" resolutions may not be illegal.


They didn't need to. There's an FCC regulation that covers all transmissions in the US which says that you can only transmit the approved modes for the particular band.

The only (psuedo) exception are the ham bands. But even there, hams decide which modes are allowed on which bands and/or frequencies within a band and the FCC will come a-knocking if someone complains that your transmitting a different mode.

There's nothing illegal about 528x480i, and I think most of us would prefer to see Weather- and all that type of crap running down there with the saved bits going back to the HD channel.

So really any resolutions are legal to broadcast in ATSC?

So really any resolutions are legal to broadcast in ATSC?

Good question, one would have to study the rules a bit. Of course, it would be just like the FCC to make certain resolutions illegal, but allow the video ES to be run at ridiculously low bit rates as some stations do.......................................:rolleyes:

All the SD subchannels in Phoenix are running at 704x480i except for Create on PBS which is running at an oddball 720x480i. The station's engineer claims they are simply rate shaping the satellite feed, though I don't have any way to confirm the original resolution since I don't have an FTA dish.

Nothing particularly oddball about 720x480i - it is the full-width digital signal whizzing around most broadcast centres (possibly minus a few lines vertically) isn't it? The 720x480 digital signal is a little wider than 4:3 or 16:9 AIUI (it is in 50Hz land), with 704x480 very close to 4:3 and 16:9 - and a slightly closer match to the analogue equivalent? AIUI the samples are the same width in these two formats, with 704 cropping 8 samples either side of the 720 digital source?

704 and 720x576 are used in European broadcasting, where the analogue (and thus 4:3 or 16:9 width picture) is equivalent to 702x576 in resolution (though many software packages - and now even some Sony HD cameras SD outputs) incorrectly treat 720x576 as 4:3 or 16:9, when in fact it should be wider. (The SD output from an HD camera issue causes a problem with virtual sets and clever motion tracked keying if you aren't careful and are using an HD camera in SD mode)

They didn't need to. There's an FCC regulation that covers all transmissions in the US which says that you can only transmit the approved modes for the particular band.

The only (psuedo) exception are the ham bands. But even there, hams decide which modes are allowed on which bands and/or frequencies within a band and the FCC will come a-knocking if someone complains that your transmitting a different mode.

Doesn't that only encompass RF modes rather than content?

Analogue broadcasts were directly modulated onto RF carriers - and thus the video waveform - sync and peak white levels, chroma levels, line-scan rates etc. had a direct effect on the RF broadcast signal, and thus the video signal itself was part of the mode definition?

However digital broadcast systems like ATSC 8VSB and DVB-T COFDM separate the RF transmission mode from the content much more significantly - so video content (or other data content) doesn't alter the RF characteristics of the broadcast?

In other words the "approved mode for bands" for digital TV would be clear on the RF characteristics of 8VSB or COFDM broadcasts, but wouldn't need to define the video, audio or data content as it would not impact the RF characteristics of the broadcasts, whereas with analogue broadcasts, the video content WOULD impact on the RF broadcasts.

So really any resolutions are legal to broadcast in ATSC?Probably. If someone can point to anything that was adopted then I will freely change my position, but I've never seen any. As far as I know, the rules for what must be carried on a DTV channel simply require that there be at least one usable, clear subchannel. The rest of the bandwidth can be used for datacasting or USDTV-style services.

Nothing particularly oddball about 720x480i - it is the full-width digital signal whizzing around most broadcast centres (possibly minus a few lines vertically) isn't it? The 720x480 digital signal is a little wider than 4:3 or 16:9 AIUI (it is in 50Hz land), with 704x480 very close to 4:3 and 16:9 - and a slightly closer match to the analogue equivalent? AIUI the samples are the same width in these two formats, with 704 cropping 8 samples either side of the 720 digital source?

704 and 720x576 are used in European broadcasting, where the analogue (and thus 4:3 or 16:9 width picture) is equivalent to 702x576 in resolution (though many software packages - and now even some Sony HD cameras SD outputs) incorrectly treat 720x576 as 4:3 or 16:9, when in fact it should be wider. (The SD output from an HD camera issue causes a problem with virtual sets and clever motion tracked keying if you aren't careful and are using an HD camera in SD mode)720 is not an odd format to see used internally or on a DVD, but I can't remember ever seeing anything broadcast in the US at that resolution. Even the high-end digital cable channels are 704, and terrestrial are usually 704, though there are the oddball 640 and lower out there. Create, like other SD services in the US, is 4:3 and hard letterboxes any 16:9 content. Apparently the source path for Create is pretty low quality and it gets bounced around the country a bit and goes through multiple encode generations before hitting AMC3 so further reencoding by the station to a better resolution will do more harm than good. The extra 16 columns are completely wasted with 8px of black showing on each side and wrecking the encoding efficiency. The sides always have heavy mosquito noise because of the sharp edge.

The tuner in my dvd burner couldn't decode that oddball resolution and there were several posts from others that couldn't watch it.

720 is not an odd format to see used internally or on a DVD, but I can't remember ever seeing anything broadcast in the US at that resolution. Even the high-end digital cable channels are 704, and terrestrial are usually 704, though there are the oddball 640 and lower out there. Create, like other SD services in the US, is 4:3 and hard letterboxes any 16:9 content. Apparently the source path for Create is pretty low quality and it gets bounced around the country a bit and goes through multiple encode generations before hitting AMC3 so further reencoding by the station to a better resolution will do more harm than good. The extra 16 columns are completely wasted with 8px of black showing on each side and wrecking the encoding efficiency. The sides always have heavy mosquito noise because of the sharp edge.


Sorry - my mistake.

Whilst 720x480(ish) is the CCIR 601 standard for SD 60Hz video, and 720x576 is a standard DVB 50Hz broadcast (and 50Hz ATSC if anyone ever deploys it) resolution, I see it ISN'T a standard 60Hz ATSC resolution.

DVB 50Hz (and 50Hz ATSC) include a significantly larger range of SD resolutions -352x288, 352x576, 480x576, 528x576, 544x576, 704x576 and 720x576 (all 4:3 and 16:9 variants)- and although I was aware that the ATSC 60Hz table was much smaller - I had assumed it carried full 601 (i.e. 720x480) as well as the closer-to-analogue equivalent 704x480.

(Interestingly the one format that doesn't have a DVB or ATSC 50Hz equivalent is the 4:3-only 640x480 square pixel ATSC 60Hz mode - which would be roughly 768x576 4:3 square pixels. I guess because 640x480 VGA was far more common than the latter... There is no accommodation for 4:3 square pixel SD in 50Hz land.)

The tuner in my dvd burner couldn't decode that oddball resolution and there were several posts from others that couldn't watch it.

Aah - I wonder if the MPEG2 decoders in the ATSC DVD recorders limits to the standard DVD resolutions - and they share MPEG2 decoding hardware between the ATSC tuner/decoder and the DVD player?

That would technically work in the US where AIUI the standard ATSC broadcast resolutions match DVD?

It wouldn't work in 50Hz territories where a wider range of formats are broadcast than are specified in the DVD spec - and ISTR that most current DVB-T DVD Recorders have two MPEG2 decoders - one for the DVB-T reception section (which decodes to YCrCb uncompressed 4:2:2 video prior to routing to the MPEG2 encoder) and a separate MPEG2 decoder for DVD replay?

(That said, I've mastered non-standard DVDs - taking 544x576 DVB-T MPEG2 programme streams and dumping them to DVD without re-encoding on my PC, and every player I own that will play DVD+/-R or RWs plays them fine)

In theory an MPEG-2 decoder should be able to display any resolution up to its technical limit at the aspect ratio the content is defined at. My cable system has all kinds of weird resolutions for SD. A few channels are 640x480. Many more are 528x480. Some on-demand SD content is as low as 320x480.

Frame rate seems to be what trips ATSC receivers. I remember reading that people have tested ATSC tuners with various ATSC-approved resolutions and frame rates and they almost always fail at anything that isn't interlaced at 1080 or 480 at 60 fields per second or progressive at 720 or 480 at 60 frames a second. I haven't heard of anyone being unable to watch my PBS station's SD channels so maybe they can handle odd resolutions.

...

In other words the "approved mode for bands" for digital TV would be clear on the RF characteristics of 8VSB or COFDM broadcasts, but wouldn't need to define the video, audio or data content as it would not impact the RF characteristics of the broadcasts, whereas with analogue broadcasts, the video content WOULD impact on the RF broadcasts.

That's not my understanding of it (although I'm far from an expert on the subject). My understanding is that it regulates all of it and for precisely the reason we are discussing it, to ensure that signals that are being broadcast in a band are compatible with receivers that are built for that band.

Otherwise, you could potentially have an OTA TV station put out a proprietry format embedded in ATSC packets and then they could try to charge money for special decoder boxes to decrpyt the signal.

Otherwise, you could potentially have an OTA TV station put out a proprietry format embedded in ATSC packets and then they could try to charge money for special decoder boxes to decrpyt the signal.

That is perfectly legal, as long as the primary stream is from the standard table. USDTV sent programming in a format that could not be decoded by a standard receiver and required the USDTV receiver.

WTVS-DT PBS in Detroit tried 720p for awhile a few years back, trying to save bandwidth for subchannels, and ended up going back to 1080i. While at 720p they were running just one additional subchannel (probably) at 480i. Both looked OK.

Now at 1080i, they have two additional subchannels (probably) at 480i. My guess is they are trimming resolution.

Aah - I wonder if the MPEG2 decoders in the ATSC DVD recorders limits to the standard DVD resolutions - and they share MPEG2 decoding hardware between the ATSC tuner/decoder and the DVD player?

That would technically work in the US where AIUI the standard ATSC broadcast resolutions match DVD?

The FCC requires all devices with OTA tuners to support ATSC, HD or not. I don't know all the aspects but basically the digital tuner will decode all the digital signals from SD all the way up to 1080i but output it internally as analog 480i and the signal is then fed into the mpeg2 encoder in the dvd burner.

Most stations transmit HD resolution signals all the time because they upconvert their SD content. An ATSC receiver limited to receiving only dvd resolutions would not be able to receive very many channels