SAP not working on Digital TVs - Page 2

This side of the pond Audio Description/Narration on OTA is done in just this manner.

On SD broadcasts a 64kbit MP2 mono audio description signal is broadcast in addition to a 192/256k MP2 stereo main programme, and viewers who want the description enable a 'receiver mix' which mixes the two signals together, removing the need to send two high-quality full mixes. The audio description audio can have metadata attached to pan it and to reduce the level of the programme sound - and viewers can alter the relative levels of the two streams.

On our newer HD OTA broadcasts we use 128k AAC-LC 2.0/320k AAC 5.1 for the main programme audio (think the bitrate switches dynamically as the audio mode is changed on a show-by-show basis) and 64k HE-AAC for the audio description feed also broadcast for receiver mixing (For some reason the AC3 implementation wasn't quite ready when the UK started HD OTA - and most chipsets wouldn't allow you to mix AAC and AC3 or AAC and MP2 - you have to use the same codecs for both the main and audio description audio streams)

And some people would be just plain wrong. In many, many ways. What's your point?

I'm not a mind reader. I have no way of knowing what people mean to say unless they say it clearly and without ambiguity. "Say what you mean and mean what you say."

It should go without saying that using largely abandoned (and never widely used) proper nouns with very specific meanings in reference to something completely different is a very poor way to try to communicate. Laypeople most often said "stereo", not "MTS", and "Español" (or whatever second language it was), not "SAP". Doing that would have been a much better way to communicate IMHO.

Although I've had many TV sets and VCRs with rotary tuning dials, I've never "dialed a TV", so I don't see your point there. Campy references like "don't touch that dial" or "film at eleven" (the latter being especially confusing to a Midwesterner) aren't vestigial at all! You seem to be looking for things that don't follow the rule you're trying to claim exists.

The thing that offends me is that after I take the time to explain precisely how my TV remotes work, that you essentially call me a liar by claiming that "the same button works for digital channels or analog channels" after I gave not one, but two separate examples of how that is not true. You will never elevate yourself by only cutting down others.

Using more decoders makes sense but we're not talking about huge savings here. My CBS station sends 384 kbps for DD 5.1 audio and 192 kbps for the DD 2.0 descriptive audio. They could save maybe a hundred kbps if the second track just had a single center channel but I doubt they'll ever crank the 5.1 stream back up to 448 kbps like it was few years ago.

Tell him to put his money where his mouth is and pay the transmitter electric bill.

That reminds me of when the Chicago indie rock station WXRT-FM moved its transmission location from the studio to where all the "big boys" were transmitting from. This move was heavily promoted with a "we're X-static" slogan that was kind of odd for a FM station that always enjoyed freedom from the "static" on the AM band.

At the time, WXRT was a local station because its original antenna height and ERP limited reception to North Side listeners. So when the new single bay antenna went online in downtown Chicago, most of the listeners who even knew that WXRT existed found that the new signal was not living up to the "X-static" claim, especially in the car.

The problem was multipath, of course. The combination of the single bay antenna's near isotropic pattern and relatively low HAAT in a place with a lot of tall buildings conspired to make the new launch a bit of a dud.

Eventually, maybe you'll be able to drop the descriptive audio to something like 64 kbps. Certainly cable and satellite will like that. They might also be able to add different languages more easily, without sending redundant program audio feeds.

Also, by sending out a "receiver mix" signal (like they are doing on the other side of the pond, says sneals) you can let visually impaired people listen to the program in 5.1 instead of mono. They can hear pretty well. They just have a problem seeing.

In the UK two approaches were taken. Satellite has more bandwidth, so just sends a second 256/192k MP2 audio stream (usually decent quality stereo) with premixed audio description.

OTA has more limited bandwidth, so the second mono 64k mono narration-only stream for receiver mixing technique is used to reduce the AD bandwidth requirements.

The former approach meant that any satellite receiver with audio stream switching is compatible without needing the ability to decoded and mix multiple audio streams (and the dominant Sky pay-TV satellite platform has facilities for
switching languages for channels with multiple audio streams - like our Welsh language channel that sometimes carries both English and Welsh audio)

The latter approach took longer to adopt, as it requires slightly more processing in the receiver (and at one point there were only a couple of brands of set top boxes that supported it). However these days it is much more widespread, so finding a compatible receiver or TV is not as difficult. It isn't universal though.

The main limitation is that set top box silicon doesn't always support mixing audio with different codecs - so you have to use the same codec family for the main audio and the second audio stream - which is why the UK is using AAC rather than AC3 (as AIUI the AC3 standard didn't support low-bandwith mono audio at the time we started)

Yeah, it's not a huge BW savings on one alternate audio, but imagine something like BYU-TV (and BYU International), or the LDS Church network.
There are many dozens of languages available on some broadcasts.
I can imagine some markets wanting to broadcast, say, three to five different languages at once. Right now, the DD5.1 is only in English.
(Sneals: How many languages do they do for the "Eurovision Song Contest"?)

Yep - it's more important for us with our SD multicast system. We have a single 24Mbs mux carrying BBC One, BBC Two, BBC Three/CBBC, BBC Four/CBeebies, etc. all of which carry audio description, along with BBC News, BBC Parliament and a BBC Interactive video stream (which itself has multiple audio feeds for sporting events). Saving 128-192kbps per channel when you are broadcasting lots of channels can mount up? I guess the BBC are saving 768kbps potentially by using receiver mix?


Ah - Eurovision. Very simple. One main programme audio - these days available in 5.1 and 2.0.

The presenters/hosts in-vision speak a mix of English (mainly), French (for some elements - particularly repeating the scores) and their own language.

In addition there are out-of-vision commentators from most of the broadcasters on-site, who separately add commentary in their own language. The hosts do not appear between every performance, but instead a "post card" or similar 30"-1'00" film (or in-arena graphic sequence) is played, and the commentators have a chance to discuss the next/previous song.

The hosts appear at certain points in the performance, where some countries will take ad-breaks. Because not all broadcasters - like the BBC in the UK, NRK in Norway, SVT in Sden etc. have commercials - the show has to work without breaks as well as with them...

So in the UK we hear Graham Norton (our commentator) out-of-vision speaking English, and the hosts of the show in-vision speaking English, French and their own language. If you are watching in Sweden for instance, then you'll get Swedish out-of-vision commentary instead of Graham.

Apols this is very off topic... But Eurovision usually is. It's an amazing show - as you can imagine any competition with 49 countries competing for a single "best song" prize is. It's been going for more than 50 years now.

These have 5.1 audio? You only save bits when you're replacing the center channel in 5.1 audio, right?

If the original audio is just 192 kbps DD2.0 then you might as well send a 192 kbps stream for every language. I recall that Dolby doesn't recommend using mono DD tracks that are less than 128 kbps.

Every tv I have except for one has a button on the remote that says either SAP or MTS. The same button switches to the alternate audio feed, if present, rather on a digital channel or an analog channel. The phrases SAP and MTS are not obsolete jsut because broadcast signals are now digital instead of analog.

Line 21 captions are still referred to as "analog captions" in every owner's manual I have, even though digital signals do not really have "analog captions".

KBYU (the local station) runs DD5.1, and a couple of stereos. The BYU channels usually broadcast two or three stereos, right now. Much of the LDS Church's musical programming and TV specials are mixed in 5.1, and many are available for syndication that way.

Of course, you could do a 3.0 mix on any show, and just substitute the dialog tracks. I'd love to do that for news, using L/R for music, effects, and nat-sound from the field. Then, the dialog could easily be in two or three languages.

Tho I have found no problems with doing that...

Then the button is mislabeled, for the ease of end user understanding. Or the remotes are older, dating back a few years. It's nothing more than a carry over that needs to be eliminated for the sake of clarity.


Sure they are. Neither one exists anymore for full power stations.

My first car, a 1966 Oldsmobile F-85, had a "Generator" light even though it didn't have a generator... it had an alternator.

In my discussion of this issue with a higher up at the NAB...I poised the question: And just how is a "sight impaired VIEWER" supposed to operate
a Tv with OSD to select SAP? The response was someone would set the Tv up for them so it stayed on SAP. Tho many Tv's and receivers I have seen default back to the main audio when the channel is changed and SAP has to be reselected...

lol

What is the correct technical term for the additional audio tracks on a digital signal? Most people, including many tv manufacturers, refer to it as "SAP".

Are you absolutely certain that every DD decoder in the world will decode a bit rate less than 128 kbps?

These are the kinds of questions I ask in meetings that make my bosses hate me.

Stream Type: 0x81 AC-3 Audio PID 4383 (0x111f)
AC3: Bitrate 56 Kbps Sample Rate 48 KHz
AC3: Mode commentary Coding 1/0 C
AC3: LFE Mode Off Dialogue normalization -23 dB
Descriptor: Registration Descriptor

And yes it does work, unless someone messes with the Tandberg...

The question is not whether the decoders can decode it, but whether the encoder can make it.

This is from the Dolby Digital Professional Encoding manual:

=======

1/0 Mono From 56 kbps, usually 96 kbps
2/0 Stereo From 112 kbps, usually 192 kbps
3/0 From 256 kbps
2/1 From 256 kbps
3/1 From 320 kbps
2/2 From 320 kbps
3/2 From 384 kbps, often 448 kbps

=======

EVERY Dolby Digital decoder can decode EVERY stream that a Dolby Digital encoder can make. (All the way up to 640kbps.) You and your bosses can rest easy.

BTW, Dolby Digital Plus (the "next generation" of Dolby Digital and often targeted for Audio Dscription uses) can do 1/0 Mono in 32 kbps. It can do 7.1 in 448 kbps (currently), and extends to 16 discrete channels in 6 Mbps (not that anyone knows what to do with all those channels yet...)

Nope..I am not..But I have not found one yet...if it can't..then it probably doesn't conform to DD specs...

ATSC Digital Television Standard: Part 6 – Enhanced AC-3 Audio System
Characteristics

(There is a complete main service and there are three types of associated services.)

6.2 Complete Main Audio Service (CM)
The CM type of main audio service shall contain a complete audio program (complete with dialogue, music, and effects). This is the type of audio service normally provided. The CM service may contain from 1 to 5.1 audio channels. Audio in multiple languages may be provided by supplying multiple CM services, each in a different language.

6.3 Visually Impaired (VI)
The VI associated service a complete program mix containing music, effects, dialogue, and additionally a narration that describes the picture content. The VI service may be coded using any number of channels (up to 5.1).

6.4 Hearing Impaired (HI)
The HI service is a complete program mix containing music, effects, and dialogue with enhanced intelligibility. The HI service may be coded using any number of channels (up to 5.1).

6.5 Commentary (C)
The commentary associated service is a complete program mix containing music, effects, dialogue, and additionally some special commentary. This service may be provided using any number of channels (up to 5.1).

http://www.atsc.org/cms/standards/a5...art-6-2010.pdf

So are tv manufacturers supposed to label the button CM/VI/HI/C ? Or simply "audio" which would confuse many users into thinking it controls the treble, bass, and speaker balance? "SAP" works much better in the real world. Very few stations broadcast fore than 2 audio streams per subchannel, so the alternate audio is the "second audio program".

No. Other than the Main Program, the other options are only available via menu settings. Further, none of the Digital TV tuners I've seen have a specific button just for switching to another language; maybe there are HDTV's out there that do, but again I've not seen them. Maybe I'll do some looking around.

Each manufacturer gives access to the other Main Programs (languages) in their own way. The different brand tuners I have, which are all outboard units, have an option in the info banner that comes up when changing channels or hitting 'Info'.

As I see it, the problem with using SAP is that it refers to a system no longer used and that alone may confuse some. If there were an addendum to the ATSC specs for a uniform name, like maybe D-SAP or SAP-D, that would be fine with me.

I have quite a few that do by the MTS-SAP button..Panasonic and LG's..and especially the govt cheeseboxes. And that is the issue I discussed with the NAb..waay too many legacy tuners out there to change now..

That's the big problem. The CE manufacturers want to own the "look and feel" of their interface, and of course they all think that their's is best.

Paraphrasing to character Zach on the show "Picket Fences" (and with apologies) "[User interfaces] are like farts. Your own is OK, but everyone else's stinks."

(BTW, he actually said "religion.")

Multiple "main programs"? That is really a confusing way to call it. My "main" I mean audio feed 1, the default, usually in English in the U.S.

I'm a retired radar engineer who understands RF. I wonder if you can point me to the posts where ERPs for different antenna gains and TPOs were discussed. I am interested in reading the two different points-of-views. I couldn't find it when I searched under your name. Thank you.

Yes, I read that and thought the same. The power will be the same but the difference will be in the antenna pattern. How much you want to fill in close and how much you want to go to the horizon. If your community of license is far away. Then higher gain antenna would help reach that, especially if you don't care about coverage close into the antenna. Once knew of a 100kw FM station that went from a 12 bay antenna at 1500ft height above ground, that reduced to a 10 bay antenna with lower gain. The transmitter was getting upgraded as well, and they wanted a more uniform pattern with smoother nulls Nearly circular pattern. They simply upped the transmitter power out to keep the 100kw ERP. Besides the better antenna pattern and coverage, how could they go from 12 bays down to 10? The first transmitter was a mid 60s transmitter, and the design probably could not put out enough power to reach the 100kw ERP the license required, so they made it up with gain off the antenna. Easier to build two more antennas then add in another power amplifier. The cost probably was prohibitive, plus tubes just could not put out the power to reach that in a single cabinet. Along with the transmission line loss going up 1500ft of the tower, even though they were using 3" rigid copper line. Plus I suspect the newer antenna designs made up for any possible loss and more control of antenna pattern.

Their latest transmitter puts out about 30kw on the ground with a single high power tube amplifier. You can hear the station nearly 150 miles out from the stick. Quite amazing what a little height will do, even when they were running 5kw temp, you could still hear them out to 100 miles. If you were in a house or building you probably could not pick them up that far out, but in a car no problem. If I were to design transmitter and antenna, I also probably would go for the somewhat lower gain antenna and more transmitter power. More even coverage, and then use transmitter power for penetration into buildings and easy reception inside homes. Rather then very high gain antenna and lower transmitter power, you may get good penetration, but your bound to end up with dead spots or deep nulls in the pattern along with putting more power to the horizon where no one might be anyway. Not interested in making distance record on reception, rather be easy to pick up in your primary market.

Sorry this was a but off topic. Interesting topic none the less about multiple audio streams. I've not found a comprehensive list of television shows with descriptive audio or Spanish dubbed audio. I do know that "According to Jim" in syndication is sent with Spanish dubbed audio as well as the original sound track. I wonder if the show aired on ABC with the Spanish dub originally. Or since the DVDs of all the seasons were released, whether the Spanish dub was added then, or if the show was aired in Spanish markets later on, that they used these dubs.
Edited by mdamberger - 6/10/12 at 4:37am

That is what I was trying to say.. and is my belief why in reality..a given ERP rating doesn't perform the same dependent upon the antenna pattern and gain.

As to your comment on multiple audio streams..see this link from FOX... http://www.hdrollout.com/bulletins/DescriptVideoTechBullv3.pdf

I have suggested to Ken H the idea of an "Official" (Tho I hate that thread term unless generated by a moderator) SAP-DVS Thread. I have added the 2nd stream to several stations in the last weeks,and the calls are starting to come in..."What's wrong with the audio?" and "When are YOU going to fix it?"