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4 posts

Wannabe Geek


# 41289 13-Sep-2009 23:25
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Hi,

I just got a little USB digital tuner (Nova-T-Stick) and this weekend set up Freeview on my PC for the first time. Everything seems to be working fine so far, but I'm a little surprised and disappointed at the quality of the audio on the TVNZ channels... all of the shows I've seen have had audio with an average bitrate of around 64 kbps which I wasn't expecting, especially on TV1 and TV2 considering they broadcast in HD.

Anyway, I was wondering if this is typical for TVNZ broadcasts (remember this is my first experience with Freeview) or do they also use higher quality audio at other times, or for certain shows? It just seems a little bizarre to me, or could there be something wrong with my setup?

Thanks.



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  # 255493 14-Sep-2009 06:37
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What you see is what you get.

Unlike TV3 TVNZ don't transmit any 5.1 AC3 feeds for HD programming. They only transmit in HE-AAC.


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  # 255502 14-Sep-2009 07:46
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The HE-AAC codec is very efficient compared to older codecs, 64kb/s on HE-AAC should be of similar audio performance to a 192kb/s mpeg1layer2 channel, according to the authorities, however the proof is in the eating of the pudding and my vote is thats not quite true.

Cyril

 
 
 
 




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Wannabe Geek


  # 255573 14-Sep-2009 13:09
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Thank you both for your relies.

So this is as good as it gets with TVNZ... seems a strange decision, I mean even Prime use a higher bitrate for their audio and Mediaworks appears to be using 128kb/s on their channels as well as AC3 on TV3.

I'm aware HE-AAC is supposed to be more efficient at low bitrates but for anyone (i.e. the authorities) to suggest that 64kb/s is similar to 192kb/s (or even 128kb/s) of competing codecs is really stretching credibility.

As you say the proof is in the eating, and to me anyway the audio sounds flat and lifeless (of the few TVNZ programs I've seen so far including the movie last night).


BTW - in the channel scan I get one called tvCentral but when I select it there's no video/audio, just curious if they are actually transmitting anything?

Thanks again.

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  # 255580 14-Sep-2009 13:35
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jeffster: BTW - in the channel scan I get one called tvCentral but when I select it there's no video/audio, just curious if they are actually transmitting anything?


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  # 255600 14-Sep-2009 14:51
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jeffster: Thank you both for your relies.

So this is as good as it gets with TVNZ... seems a strange decision, I mean even Prime use a higher bitrate for their audio and Mediaworks appears to be using 128kb/s on their channels as well as AC3 on TV3.

I'm aware HE-AAC is supposed to be more efficient at low bitrates but for anyone (i.e. the authorities) to suggest that 64kb/s is similar to 192kb/s (or even 128kb/s) of competing codecs is really stretching credibility.

As you say the proof is in the eating, and to me anyway the audio sounds flat and lifeless (of the few TVNZ programs I've seen so far including the movie last night).


BTW - in the channel scan I get one called tvCentral but when I select it there's no video/audio, just curious if they are actually transmitting anything?

Thanks again.


What codec are you using for this on a PC and have you compared the audio with a certified STB?




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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  # 255610 14-Sep-2009 15:21
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The answer lies here: http://www.geekzone.co.nz/forums.asp?forumid=83&topicid=32085

From what I can gather Dolby Digital from TVNZ is in the works but there is currently no "release date" so to speak. Just a typical wishy washy "soon" answer.

From my experience, no matter what hardware you use, TVNZ DVB-T audio quality is just not there yet! I guess we have to wait for TVNZ to implement Dolby Digital. Waiting....waiting.....waiting.......



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Wannabe Geek


  # 255624 14-Sep-2009 15:50
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@ rhysb

Thanks, that explains why I get nothing for tvCentral.

@ openmedia

Well Monogram AAC filter for live viewing, and I've also listened to the extracted audio in Winamp (which uses Coding Technologies decoder I believe) and they both sound the same... I haven't compared it to a STB but I doubt they perform any kind of magic that would make a difference, it's a ~64kb/s stream afterall.

@ dontpanic42

Thanks for the link and I agree with you!


 
 
 
 


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  # 255662 14-Sep-2009 17:32
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jeffster:
@ openmedia

Well Monogram AAC filter for live viewing, and I've also listened to the extracted audio in Winamp (which uses Coding Technologies decoder I believe) and they both sound the same... I haven't compared it to a STB but I doubt they perform any kind of magic that would make a difference, it's a ~64kb/s stream afterall.



I find if I watch freeview|HD with AAC under EyeTV on a Mac it sounds dreadful, but under Mplayer or MythTV on Linux it sounds close to the MP2 audio streams they use on DTH.

I'll admit that neither as as good as the AC-3 stream on TV3.




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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Wannabe Geek


  # 255905 15-Sep-2009 16:39
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openmedia:

I find if I watch freeview|HD with AAC under EyeTV on a Mac it sounds dreadful, but under Mplayer or MythTV on Linux it sounds close to the MP2 audio streams they use on DTH.

I'll admit that neither as as good as the AC-3 stream on TV3.


Okay I see what you were getting at now.

I forgot to mention I've also used VLC to play back some recorded files.
Since the aac decoder used by the monogram filter and VLC are both based on the libfaad2 library (same too with Mplayer I believe) there should be no problems there.


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  # 256005 16-Sep-2009 08:19
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dontpanic42: The answer lies here: http://www.geekzone.co.nz/forums.asp?forumid=83&topicid=32085

From what I can gather Dolby Digital from TVNZ is in the works but there is currently no "release date" so to speak. Just a typical wishy washy "soon" answer.

From my experience, no matter what hardware you use, TVNZ DVB-T audio quality is just not there yet! I guess we have to wait for TVNZ to implement Dolby Digital. Waiting....waiting.....waiting.......



We are still waiting waiting  waiting, They are still planning and building at this stage. But a will be a while before you see or hear anything. This new system will be seriously and thoroughly checked for a long time time before it sees the airwaves.

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