Author Topic: Channels 7 & 10 - low SD bitrates ? (but ch7 improved now)  (Read 6849 times)

Offline chopper

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Channels 7 & 10 - low SD bitrates ? (but ch7 improved now)
« on: March 30, 2008, 09:17:07 PM »
Adding to http://www.icetv.com.au/iceforum/index.php?board=1.0 about channel 7 Adelaide AFL game Adelaide vs Western Bulldogs,

the AFL game on channel 10 SD last night Adelaide vs West Coast was ALSO quite blurry and blocky (no it ISN'T my setup nor reception, I have almost new quality Sony gear and other good gear and shielded cables and high signal strength and quality and line of sight etc). 

The game broadcast bitrate was a lot less than 6Mbps more around 5 mark or less at times - nowhere up near what's good for fast-moving sports footage with lots of combined panning and zooming and action movement, a higher bitrate up around the 8-9Mbps  would yield a much more watchable result for viewers.  DVD's can get up around  9Mbps which is definitely in-spec depending on the audio bitrate.

Does anyone know if it's a deliberate ploy by the channel(s) to make their HD seem better by comparison ?

Welcome to digital.. currently the place for blocky action sports pictures.  Peanuts.
« Last Edit: May 18, 2008, 09:35:31 PM by chopper »

Offline chopper

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Re: Channels 7 & 10 - low SD bitrates ?
« Reply #1 on: April 05, 2008, 10:53:31 AM »
Well, just peeked at a portion of channel 7 SD footy last night, and the bitrate was up around the 5-6 Mbps mark.    Still blocky in fast action, but better than before !

Cheerio Channel 7, you made an improvement. 

Now, lets see if Channel 10 has any brains to recognize its failings and do better than serve up crap bitrates to its viewers ...


Offline chopper

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Re: Channels 7 & 10 - low SD bitrates ?
« Reply #2 on: April 13, 2008, 05:25:07 PM »
Well done, channel 7 - nicer broadcast !   :D  The SD bitrate was bang up on the 6Mbps mark (didn't see the HD unfortunately).  Kudos go to you for learning !  8)

Offline chopper

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Re: Channels 7 & 10 - low SD bitrates ?
« Reply #3 on: April 20, 2008, 09:18:29 AM »
OK, channel 10 for this weeks footy.  Not sure what to make of the SD bitrates, though - above 6Mbps some of the crows game (1st half) and more toward 5Mbps (2nd half).  A tad blocky at times but as good as if not better than 7, visually ?  So a well done channel 10 !

Offline chopper

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PATHETIC broadcast, channel 10
« Reply #4 on: April 26, 2008, 08:00:36 PM »
Channel 10, you are PATHETIC.   :'(  :-\  ??? 

Your SD AFL broadcast of the Adelaide game - live sports field action with lots if movement etc - and the ff'ing best you can manage is an average bitrate of 4.7 to 4.8 MBps for SD when you have MUCH more bandwidth available to use if you had the brains to do so. 

Channel 7 manages more than that !!  The HD bitrate apparently averaged 16Mps... so - purposely skewing the HD quality to appear better, for your own purposes, are you ?

Low bandwidth = pith poor blocky picture quality as compared to higher bitrates ESPECIALLY for that type of content.  Fools and charlatans.

Channel 10, your heads should have holes in them to let the shite out and your AFL broadcast rights taken off you.   You don't deserve the rights, dishing up that SD shite to the people who, in the end, pay your bills.
« Last Edit: May 05, 2008, 09:17:43 PM by chopper »

Offline chopper

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Re: Channels 7 & 10 - low SD bitrates ?
« Reply #5 on: May 05, 2008, 09:20:37 PM »
Well, channel 10 brought up their bitrate of the Adelaide game this week to an average of 5.7 or more Mbs. 

Nice one Channel 10, well done.  Could be higher, but good one as compared to last week, nevertheless.   :)

Let's hope both channels stay good and don't spiral back down the path of pith-poor broadcasting.

Offline chopper

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Re: Channels 7 & 10 - low SD bitrates ? (but ch7 improved now)
« Reply #6 on: May 18, 2008, 09:34:27 PM »
My my, Channel 7 have lifted their game SD bitrate-wise... bang up on 6Mbps for each quarter of the Adl vs Melb game.

Well done Channel 7, well done.  Your broadcast has a better chance of being good for your customers.  ;)

Just wondering - if there's some reason for the channels not choosing action broadcast bitrates aligning with the DVD-spec max of ~9Mbps and hence achieving a much smoother action broadcast ?  It's a well-established rule (try it yourself, or google video forums) that that higher bitrate makes it possible to yield a higher quality action footage viewing experience (if you don't f*ck up the encoding and make it blocky regardless of bitrate).   HD is broadcast at a much higher bitrate, so it's not a "technical" limitation in that sense.
« Last Edit: May 18, 2008, 09:39:48 PM by chopper »

Offline prl

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Re: Channels 7 & 10 - low SD bitrates ? (but ch7 improved now)
« Reply #7 on: May 18, 2008, 11:08:35 PM »
My my, Channel 7 have lifted their game SD bitrate-wise... bang up on 6Mbps for each quarter of the Adl vs Melb game.

Well done Channel 7, well done.  Your broadcast has a better chance of being good for your customers.  ;)

Just wondering - if there's some reason for the channels not choosing action broadcast bitrates aligning with the DVD-spec max of ~9Mbps and hence achieving a much smoother action broadcast ?  It's a well-established rule (try it yourself, or google video forums) that that higher bitrate makes it possible to yield a higher quality action footage viewing experience (if you don't f*ck up the encoding and make it blocky regardless of bitrate).   HD is broadcast at a much higher bitrate, so it's not a "technical" limitation in that sense.
They only have a certain bit budget in the channel, and that can only be increased by changing the coding parameters, at the cost of making the transmission more susceptible to noise.

Edit: There's a table of the modulation parameters, maximum channel bit rate, and the required C/N (Carrier/Noise ratio) for DVB-T in  ACMA Digital terrestrial television broadcasting planning handbook - March 2005: Appendix B, DVB-T Modulation Schemes.
« Last Edit: May 19, 2008, 10:06:46 AM by prl »
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Offline chopper

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Re: Channels 7 & 10 - low SD bitrates ? (but ch7 improved now)
« Reply #8 on: May 19, 2008, 11:46:32 PM »
Nice pickup, prl.   

Seems at face value that 9Mbs is allowable in all modulations by the look of the tables (with limited understanding)... as you say "by changing the coding parameters, at the cost of making the transmission more susceptible to noise". 

Given HDTV is broadcast at about 13-15 Mbps all day every day by the looks, one presumes it's achievable one way or another if they wanted to... say, by changing the modulation (if it isn't already the right one... how can we tell ?) to their HDTV equivalent and then broadcasting at the desired lesser bitrate than HDTV requires and/or with "lesser noise suseptibility" code-rate/guard-interval parameters :)  I wonder if they can readily change those things "on the fly" on a per-programme basis.

Just think of the trade-off .. possibly a "superb" sports action viewing experience vs a tad of noise.  Digital telly's have inbuilt noise processing gear in them anyway, don't they... I recall my Sony does in some way ?

I'm sure there's gotchas in that, as I hope someone will point out.  Thanks again.
« Last Edit: May 19, 2008, 11:54:08 PM by chopper »

Offline prl

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Re: Channels 7 & 10 - low SD bitrates ? (but ch7 improved now)
« Reply #9 on: May 20, 2008, 06:36:28 PM »
Nice pickup, prl.   

Seems at face value that 9Mbs is allowable in all modulations by the look of the tables (with limited understanding)... as you say "by changing the coding parameters, at the cost of making the transmission more susceptible to noise". 

Given HDTV is broadcast at about 13-15 Mbps all day every day by the looks, one presumes it's achievable one way or another if they wanted to... say, by changing the modulation (if it isn't already the right one... how can we tell ?) to their HDTV equivalent and then broadcasting at the desired lesser bitrate than HDTV requires and/or with "lesser noise suseptibility" code-rate/guard-interval parameters :)  I wonder if they can readily change those things "on the fly" on a per-programme basis.

Just think of the trade-off .. possibly a "superb" sports action viewing experience vs a tad of noise.  Digital telly's have inbuilt noise processing gear in them anyway, don't they... I recall my Sony does in some way ?

I'm sure there's gotchas in that, as I hope someone will point out.  Thanks again.

The problem is not the bitrate of the SD service alone. For example, in Canberra, the ABC transmits in a 7MHz bandwidth channel centered at 205.625 MHZ from Black Mountain using a certain modulation scheme for the whole channel. That channel carries a single digital bitstream that is then split out (demultiplexed) into the individual streams for the services on that channel: ABC 1, ABC 2, ABC 3, ABC HD, Dig Radio and DiG Jazz Radio.  Because of that, the sum of the bitrates for all the services on a channel has to be less than the channel bitrate. The ACMA table just gives the channel bitrate, which must be shared between the services on that channel. To carry an SD service at 9Mbps and a HD service at 12Mbps the channel needs a 21Mbps bitrate.

You can change the channel bitrate by changing the modulation parameters, but if you do that to increase the bitrate of the channel, you make the data carried by channel more susceptible to noise. That's a particular case of a general rule - the noisier a channel is, the lower its maximum bitrate is.

Offline chopper

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Re: Channels 7 & 10 - low SD bitrates ? (but ch7 improved now)
« Reply #10 on: May 20, 2008, 07:25:52 PM »
Ah, all becomes clear.  Thanks prl.   

I guess the channels would have done tests re "acceptable noise", and settled around 6Mbps for SD by the looks.

Oh well, hopes for "superb" SD sports action experience fade ...



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