mhyland,

Sorry to pepper you with questions, but I'm curious if you know when the Ottawa
transmitter will go live? Thanks.

cheers,
aaron

Update on Potter picture issue: Film mode is supposed to detect content that has a 3:2 pulldown and run that content through a different encoding algorithm which optimizes bandwidth. With film mode off, the problem goes away.

Glad to have you on board.

Any idea how film mode should help compression on an interlaced output? The 1080i output still uses the 3:2 conversion and will still compression each of the interlaced frames individually. When outputing in progressive mode, the 3:2 pulldown allows better compression on each progressive frame as each frame equates to a complete film frame, even with the extra full frames inserted. It seems that your convertor is deinterlacing and reinterlacing the signal. This feature may not be meant for broadcasters outputing in 1080i.

Any news on correcting the audio output to match the number of channels of the source material?

We appreciate being treated with respect and intelligence, so thanks again!
I second that - it sure beats the form letters we get from Global, CTV, and ExpressVu.

Thanks 57.

Update on Potter picture issue: We had the Tandberg folks in yesterday to test the broadcast encoders. We were able to reproduce the problem by running the version of Potter on our servers through a spare encoder with the encoder's Film Mode button on, as it was on Sunday. Film mode is supposed to detect content that has a 3:2 pulldown (eg filmed content like Potter and the Peter Cottontail clip from Saturday) and run that content through a different encoding algorithm which optimizes bandwidth. With film mode off, the problem goes away. We are looking at the original master and our post production process to see if we introduced something that would throw the encoder off, because Film Mode should be a useful feature.


Thanks for the update!

Can you talk about the process at all?

What is the form of the master, and the format? How does it arrive?

Do you encode to a server sometime before airtime, and broadcast that? Or do you encode real-time when broadcasting?

Does everything get wiped after broadcast, or are you permitted to retain a broadcast ready copy for next time?

What gets sent to the cable/sat companies?

Could you deliver a high-bit rate encoding to a cable/sat company if they were to wish to adopt a new broadcast encoding (e.g. MPEG-4), or would always be limitted to an ATSC format?

Gary

... I'm curious if you know when the Ottawa transmitter will go live? Thanks.

We have submitted the application for French and English transmitters in Ottawa. So the CRTC has to consider the application. If it is approved, we'll have up to two years to fire up the transmitter. A guess (and it's only a guess) would be late 2006...

Any idea how film mode should help compression on an interlaced output?
My understanding--and it is a comparatively recent and perhaps tenuous understanding -- is that film mode on the encoder looks for the field pattern associated with material that has been converted from film to video. It can then compress these fields more efficiently.

I'm sure you've all been through this elsewhere on the site with better guides, but briefly, 2:3 pulldown is the method used to convert film content at 24 frames/second to video content at 60 fields/second. Frames A and B of film are converted to fields A:A:B:B:B of video. Every two film frames converts to five video fields, so 24 frames * 5/2 = 60 fields. To complicate things, the precise numbers are 23.98 film frames to 59.94 video fields.

In Film mode, the encoder looks for the A:A:B:B:B pattern and says, hey, this is film material--All I really need to worry about compressing is A and B. That is my understanding, anyway...


Any news on correcting the audio output to match the number of channels of the source material?
Can you explain this question a little more? Although our transmitter is capable of broadcasting in 5.1, much or our material is still stereo. So although the 5.1 light may be on on your system, you'll only hear stereo for most programs. There is a documentary coming in 5.1 on April 13th...

Although our transmitter is capable of broadcasting in 5.1, much or our material is still stereo. So although the 5.1 light may be on on your system, you'll only hear stereo for most programs. There is a documentary coming in 5.1 on April 13th...If the programming is indeed stereo, then we are missing nothing, however, if the programming were Dolby Pro Logic (DPL), then we are missing something. Let me explain.

You are currently sending DD5.1 all the time. If a DPL programme gets sent as two-channel DD5.1 (instead of DD2.0) then anyone with an A/V receiver connected via a digital connection will hear "stereo" only. ie - sound from the LF & RF speakers. What we really want to hear is DPL if it is present. Sending DD5.1 all the time also causes dialogue to come from the LF & RF speakers instead of the center channel as it should (unless the material is DD5.1)...

The only workaround for consumers is to force the receiver to listen to the analogue stereo signal (if you have it connected) and then it would be decoded in DPL.

By always sending DD5.1, any DPL is "sacrificed" for many people. It would be "proper" for CBC to send DD2.0 for all "stereo" (or DPL) programmes and DD5.1 for all DD5.1 programmes.

However, we don't want you to forget to "throw the switch" when there really is a DD5.1 programme, because we want to hear that. If there's a likelihood that you'd forget to "throw the switch", we'd probably all prefer that you continue to send DD5.1 full time, since it's not a huge issue.

I hope this is clear.

Questions.

1. Is it possible to automate the above? (DD2.0 to DD5.1?)

2. Is the "switching" between HD programmes and SD programmes automatic? Or does someone manually switch these? Is the switch between the HD programme and the SD commercials automatic? (I realize that everything is sent out as 1080i)

As far as other providers, we certainly expect the satellite folks will carry us soon. I've heard they may have up to 90 days,

--mark

This is a total joke - The CRTC should give both Bell and Shaw 5 days to get CBC HD available.

The nerve of Bell to show 2 feeds of the PBS demo loop- but no CBC HD

.. and Shaw - the real joke - SC HD ch 290 is sitting there vacant - the UHF antenna and HD encoder is sitting there atop the SC building in Mississauga doing nothing except for the couple of hours/week of CITY HD

It's no wonder the CRTC turned down the Shaw application for satellite when they first issued them - the Liberal government should be publically chastizing these 2.

Come on JRs - cash in your stock - sell Shaw Communications and go buy your own island someplace - anywhere but in Canada - you two have worn out your citizenship.

In Film mode, the encoder looks for the A:A:B:B:B pattern and says, hey, this is film material--All I really need to worry about compressing is A and B. That is my understanding, anyway...
This is great when your final output is progressive, but the encoder will have to reconvert to the interlaced output that you transmit, thus losing the benefit of compressing the full A and B frames. It might be wise to leave it off for CBC's purposes.

Can you explain this question a little more? Although our transmitter is capable of broadcasting in 5.1, much or our material is still stereo. So although the 5.1 light may be on on your system, you'll only hear stereo for most programs. There is a documentary coming in 5.1 on April 13th...
As 57 stated, transmitting the stereo program in a 5.1 stream prevents automatic decoding by Dolby Pro Logic which repositions dialog to the centre channel. However, I disagree with 57's statement that we'd rather leave it this way if there's a chance of not flipping the switch for 5.1 material. I find it extremely annoying when the centre channel cannot be decoded. Hopefully your equipment can auto-sense the source and flip the mode as required.

1. Is it possible to automate the above? (DD2.0 to DD5.1?)
I'm told we are not able to to automate the audio switch.


2. Is the "switching" between HD programmes and SD programmes automatic? Or does someone manually switch these? Is the switch between the HD programme and the SD commercials automatic? (I realize that everything is sent out as 1080i)
Our manager of presentation tells me: "The switching between the SD and the HD is done by the automation system. Having said that, there needs to be manual entry in the automation play list to select the correct type of upconversion. For example, if a program is letterbox we use one upconverter as opposed to the other one that upconverts 4:3 programs. Commercials are just played out of the SD play list and are run by the automation and upconverted."

You certainly raise a good point about Pro Logic. As we continue to build our processes around the HD channel, I'll see if we can identify which programs are in Pro Logic and if we can transmit those properly, rather than in 5.1.

--mark

Thank you very much for the responses. I hope that we are providing as much useful information to you as you are to us.

It's great that you are upconverting the widescreen programmes to 16:9 fullscreen, instead of leaving them windowboxed. We all wish more HD channels did this.

Does anyone know if there is a way to get a listing of the programs broadcast by CBC that are actually in HD? I don't see that indicaton on any program guide.

I believe Mark said earlier in this (or another) thread that this was something they were working on.

Great to have you onboard Mark!

I was wondering SRC will be broadcasting Lost and desperate house wife in French. Both show are normaly in HD in English.

Do you know if it will air in HD on SRC?

So what's up with Express Vu?

Any update as to when CBC HD is coming?

So what's up with Express Vu?

Any update as to when CBC HD is coming?


I got the following reply from Bell ExpressVu today -

"Thank you for taking the time to contact us regarding CBC HD. We hope
that you are enjoying your Bell ExpressVu Satellite system.

We have been advised that CBC HD will be added to our line up this
month, however, a specific date was not provided. We look forward to
adding another HD channel to our growing lineup in the near future."

This is great when your final output is progressive, but the encoder will have to reconvert to the interlaced output that you transmit, thus losing the benefit of compressing the full A and B frames. It might be wise to leave it off for CBC's purposes.


The output doesn't need to be progressive to benefit from reverse 3:2 encoding.

Think of it like this:

24fps film -> 3:2 pulldown -> 60i tape (NTSC), now with 25% "more" material from duplicate fields -> reverse 3:2 pulldown (back to 24 fps, lossless) -> HD upscale and MPEG encoding for broadcast (25% less material than 60i, and no "jaggies" that cause upscaling/compression headaches) -> Broadcast as 24fps stream -> Cable, OTA, Satellite box adds pulldown before sending HD60i signal to TV.


The key here is, removing pulldown makes upscaling and compression *much* easier and cleaner.

The same concept is applied to upscaling DVD players.


-- Jackalope

24fps film -> 3:2 pulldown -> 60i tape (NTSC), now with 25% "more" material from duplicate fields -> reverse 3:2 pulldown (back to 24 fps, lossless) -> HD upscale and MPEG encoding for broadcast (25% less material than 60i, and no "jaggies" that cause upscaling/compression headaches) -> Broadcast as 24fps stream -> Cable, OTA, Satellite box adds pulldown before sending HD60i signal to TV.The flaw in this statement is that the signal sent from the CBC is a 1080i signal. The compression of an interlaced signal is compressed separately on each of the half-frames representing the odd and even scanlines, introducing various artifacts. Only a progressive output signal will compression on the whole frame, which provides better compression rates.

BTW, we were also referring to the HD source, but is equally applicable to the NTSC upconverts.

The flaw in this statement is that the signal sent from the CBC is a 1080i signal. The compression of an interlaced signal is compressed separately on each of the half-frames representing the odd and even scanlines, introducing various artifacts. Only a progressive output signal will compression on the whole frame, which provides better compression rates.

BTW, we were also referring to the HD source, but is equally applicable to the NTSC upconverts.


Do you know for sure that inside the MPEG stream there are actually 60 discreet fields when encoding film material?

If they can encode DVDs with 24fps material (and the let the player add the pulldown), why would the same principle not be applied to HD MPEG encoding? Encoding 60 discreet fields for film material (which has only 48 unique fields) seems wasteful.

Either way, even if it is really broadcast at "real" 60i, doing a reverse 3:2 on the material in order to upscale it makes total sense. (for upscaled shows, of course).

-- Jackalope

Matey,

Since you made me wonder "Do all 1080i signals actually carry 60 discreet fields *all the time*?", I did a quick research on the ATSC's website and found this document:

http://www.atsc.org/standards/a_53c_with_amend_1.pdf

According to the table on page 31 ("Compression Format Constraints") of the PDF, it is OK for the broadcaster to transmit a 1920x1080 MPEG stream with a framerate of 23.976 Hz with the "progessive" flag set to "on".

-- Jackalope