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80 posts

Master Geek


# 20902 9-Apr-2008 15:00
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Hi all,

I was watching TV3 Freeview today around 2:30pm, after finally getting my DVB-T setpup working, and I noticed they were broadcasting with the following attributes:

reported in DVB Viewer
1920x1088 25fps (video)
128 Kbps 24.0 Khz (audio)
10.1 MBits (stream)

Is this common for TV3 or was somebody taking the piss to see if they could choke as many PCs as possible?

Thanks

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  # 122327 9-Apr-2008 15:07
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Nirodha: Hi all,

I was watching TV3 Freeview today around 2:30pm, after finally getting my DVB-T setpup working, and I noticed they were broadcasting with the following attributes:

reported in DVB Viewer
1920x1088 25fps (video)
128 Kbps 24.0 Khz (audio)
10.1 MBits (stream)

Is this common for TV3 or was somebody taking the piss to see if they could choke as many PCs as possible?

Thanks


TV3 are transmitting in 1080i with 128k HE-AAC with SBR at around an average of 10MBit.

What makes you think that they are "taking the piss"?




Generally known online as OpenMedia, now working for Red Hat APAC a Technology Evangelist and Product Manager. Still playing with MythTV and digital media on the side.


134 posts

Master Geek


  # 122350 9-Apr-2008 16:21
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Certainly not common but the TV3 press release has more info:

http://www.scoop.co.nz/stories/BU0803/S00308.htm

Google rocks - TV3 HD - threw up plenty of results......

 
 
 
 




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Master Geek


  # 122410 9-Apr-2008 20:48
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The reason I thought they were taking the piss is because a resolution that high is wasted on anything less than a 50 inch display. I don't know about you all, but I don't know of anyone running such a large LCD or Plasma right now. Also, that audio stream is overkill; They could get CD transparent sound with a 96 kbps stream.

Cheers

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  # 122415 9-Apr-2008 20:57
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Nirodha: The reason I thought they were taking the piss is because a resolution that high is wasted on anything less than a 50 inch display. Also, that audio stream is overkill; They could get CD transparent sound with a 96 kbps stream.

Cheers


Actually I can tell the difference on my Dell 2407wfp display which is 24"

Really it depends on the size of your lounge, distance to screen etc. For my own setup lounge most people would be able to tell the difference on a 42" set but I'd probably notice on a 32"

And what do you mean by "CD transparent sound with a 96 kbps stream". Their 128K HE-AAC audio sounds good, but it definately isn't CD quality.




Generally known online as OpenMedia, now working for Red Hat APAC a Technology Evangelist and Product Manager. Still playing with MythTV and digital media on the side.




80 posts

Master Geek


  # 122423 9-Apr-2008 21:09
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Can you tell with difference between TV3 and the FreeviewHD preview channel? I certainly can't - as a matter of fact, the FreeviewHD preview actually looks nicer to me.

As for CD transparent sound, they could get that if they were sampling at 44 Khz instead of 24 Khz. Sampling at 24 Khz is basically only capturing 0 Hz to 12 Khz - half the human hearing frequency range. Sampling at 44 Khz captures 0 Hz to 24 Khz - basically the entire human hearing frequency range. Even then they could use LC-AAC at => 92 Kbps for it and would not be wasting the bandwidth they are at 128 Kbps. HE-AAC really doesn't buy one anything until one starts encoding at low bitrate; say <= 48 Kbps.

Cheers

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  # 122424 9-Apr-2008 21:13
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Nirodha: Can you tell with difference between TV3 and the FreeviewHD preview channel? I certainly can't - as a matter of fact, the FreeviewHD preview actually looks nicer to me.


You seem to contadict yourself slightly there!

Considering the HD Preview channel is running HD content 24/7 it should look nicer than TV3 who are only showing some HD content.

Getting back to the original comment about choking PC's..I don't agree with this at all, the only requirement to get Freeview properly is a reasonable spec PC and a video card capable of H.264 acceleration (such as a $110 NVidia 8500) and appropiate codec.



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Master Geek


# 122427 9-Apr-2008 21:17
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sbiddle, yeah, I know I contradicted myself with the above. But, such is life.

 
 
 
 


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  # 122430 9-Apr-2008 21:19
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Nirodha: Can you tell with difference between TV3 and the FreeviewHD preview channel? I certainly can't - as a matter of fact, the FreeviewHD preview actually looks nicer to me.


Really depends on the content. As has already been mentioned all of the content on freeview|HDTM is HD. Some content looks better in 720p others in 1080i. What I should have said is I can tell the difference between a 1080 native set and a 720 native set

Nirodha:
As for CD transparent sound, they could get that if they were sampling at 44 Khz instead of 24 Khz. Sampling at 24 Khz is basically only capturing 0 Hz to 12 Khz - half the human hearing frequency range. Sampling at 44 Khz captures 0 Hz to 24 Khz - basically the entire human hearing frequency range. Even then they could use LC-AAC at => 92 Kbps for it and would not be wasting the bandwidth they are at 128 Kbps. HE-AAC really doesn't buy one anything until one starts encoding at low bitrate; say <= 48 Kbps.

Cheers


The are doing HE-AAC with SBR which produces 48KHz output. Hence the 128k bit rate is quite reasonable.

With SBR the AAC does 24K and the SBR does the other 24K.




Generally known online as OpenMedia, now working for Red Hat APAC a Technology Evangelist and Product Manager. Still playing with MythTV and digital media on the side.




80 posts

Master Geek


  # 122439 9-Apr-2008 21:48
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sbiddle:
Getting back to the original comment about choking PC's..I don't agree with this at all, the only requirement to get Freeview properly is a reasonable spec PC and a video card capable of H.264 acceleration (such as a $110 NVidia 8500) and appropiate codec.


LOL! You don't have to agree with me. It's not a debate! Cool 

I'm trying to run this DVB-T stuff on a rather low spec laptop at the moment. It handles all the Freeview stuff just fine, except it will stutter a little bit with TV3; hence my complaint. Also, with my formerly being a computer programmer, I'm always on the lookout for the balance of quality and efficency.

openmedia, I have a background in audio engineering as well. And,  I don't find that particular usage of AAC encoding to be reasonable. 

I suspect that someone at TV3 doesn't fully understand the LC, HE and SBR aspects of the AAC codec. If they did they would not being running a HE encoded stream at that high of a bandwidth, as it's a waste of resources. And, at 128 Kbits, the SBR stream will be virtually all zeros.

HE and SBR are meant for low bandwidth applications. Low being 48 Kbps or less.

Actually I'm surprised that they could even encode their audio in such as way, as most standard AAC encoders will default to LC for any bandwidth above 64 Kbps or so, regardless of the parameters the user tries to enforce.

No offence if any of you guys work for TV3. I'm just voicing my opinion. Tongue out


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# 122441 9-Apr-2008 22:06
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HE AAC however is actually quite processor efficient though 128k AAC with Sbr is certainly rather suprising and seems a interesting choice.

I'd have suggested sticking with LC at the 128Kbps level as I have found anything above 64KBps with HE is a waste of bytes and can even degrade the audio. I think they should have gone all the way and simply shot the audio rate up to 192 and stuck with LC coding especially when they are utilizing a huge 10megabits for video which is insane but greatly welcomed, while you may enjoy staring at 640 x 480 displays I welcome the clarity on the big screen!!! :-D

The difference on the plasma is noticeable (only a 42" 720p screen) and on my 22" (1080p) pc lcd display it's really apparent.

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  # 122442 9-Apr-2008 22:32
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Well the other thing is it is part of the DVB Spec - http://wiki.ebu.ch/bgav/images/4/4e/Tm1214r27.avc0075r15.2.dTS101154V1.7.1.doc

I'd rather they did a higher bit rate personally. Based on HE-AAC, AAC, MP3, CD and DVD-Audio samples through the same setup nothing is as good as DVD-Audio, but HE-AAC is way better than AAC and MP3.




Generally known online as OpenMedia, now working for Red Hat APAC a Technology Evangelist and Product Manager. Still playing with MythTV and digital media on the side.


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  # 122479 10-Apr-2008 10:00
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Isn't UHD 7680 × 4320 anyway?

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  # 122561 10-Apr-2008 16:06
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I had a look at the output of what I am hearing on dvb-t, and there is content over 24kHz in the output from dvbviewer so there must be the SBR happening. It still sounds like total crap.

I have my desktop PC hooked to an ok stereo so I cant really compare it with analog tv's nicam, but from what I remember when I had a tv hooked up to a decent system the audio on C4 was a hell of a lot better then it is on dvb-t.

I cant really watch the others since the PC is too crap to decode HD stuff at a framerate that isnt hard to watch.




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Master Geek


  # 122573 10-Apr-2008 16:23
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From my understanding TV3 is upscaling standard 576 broadcast to 1080i using the full 10 mbs.  Only then they have HD content do they display the "HD where available" logo at the start of the program.  Does anyone have a definitive list of these programs yet?

I saw the following in HD and they were excellent, but noticed Bones was a little soft focus on people, crystal clear on scenery shots, maybe they are going easy on actors who are comlaining that HD shows all their imperfections!

Programs:

CSI
Bones
My Name is Earl
So You Think you can Dance
House

Any more?

Also it was my understanding that the HE-AAC codes suported multiple channels, hence 128 k may allow 5.1?  Is this true?


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  # 122601 10-Apr-2008 16:55
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smbunn:

Also it was my understanding that the HE-AAC codes suported multiple channels, hence 128 k may allow 5.1? Is this true?



There are no plans for 5.1 in HE-AAC, it will be in AC-3.




Generally known online as OpenMedia, now working for Red Hat APAC a Technology Evangelist and Product Manager. Still playing with MythTV and digital media on the side.


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