Just wondering if anyone here knows the audio data rate for the Freeview BBC HD channels? I note that they use HE-AAC but am currently unable to detect the data rate directly.
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Looks like it is 128kbs AAC stereo or 320kbps Dolby 5.1
See this...
Eric -
Thanks Eric - been looking for that info for ages...Comment
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Indeed, many thanks Eric.Comment
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Moved in what sense? The data rates are as they were: 256kbps mp2 for standard definition, and 128kbps (2 channel stereo)/320kbps (5.1 surround) HE-AAC for 'high' definition.Originally posted by OldTechie View PostComment
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Ah, thanks.Originally posted by Dave2002 View PostMoved as in the link given in msg 2 no longer works.
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Just wanting to be sure I understand what this means. If you listen to the sound of a BBC HD channel on stereo, the bit rate is 128 kbps? Is that correct? So not as good as radio 3 HD then? Thanks.Originally posted by OldTechie View PostComment
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Quite. Indeed, with only half the data rate (though using a rather more efficient codec) of the standard BBC Television channels, it quite possibly offers lower two channel stereo audio quality than 'bog standard' BBC2 or BBC4. Pretty much on a par for potential audio quality with Radio 3 DAB at 192kbps mp2.Originally posted by David-G View Post
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Well, you might get Dolby surround sound at 320kbps. How good that is I have no idea. In my simplistic view, radio 3 HD gives you 160 kbps of AAC compressed per audio channel, whereas Dolby 5.1 at 320 kbps gives you an average of a bit less than 64 kbps AC3 compressed audio for each full bandwidth channel (the LFE channel should not need very much because the sample rate can be much less.) I'm sure you would find some people who find the surround sound effect more beneficial than the higher bit rate per channel, and others who would prefer the alternative.
For plain stereo, the sound on the SD tv channels looks to hav a higher data rate but older compression type than the HD channels. I guess the sample rate on both will be 48kHz.
Note that the figures are not from an official site. I don't think you can find a formal public statement from the BBC. It may be more complex than the tables suggest.
There are other differences between a TV feed and the Radio 3 feed. If you have a close up of an instrument combined with sound as if you were 100 ft away in the audience, it may jar. They seem to do it less obviously these days but there was a time when the TV audio sounded quite strange without the pictures because the mix was tweaked quite severely as the shots changed. Also, TV audiences generally want everything at a nice constant level, so the dynamics may be compressed manually in the mix. You will find that the TV mix is often very different to the radio mix - and that difference is much more significant than the data rates. I find that turning on the TV picture whilst listening to the radio 3 HD feed is not very satisfactory. The pictures spoil the sound! If we must have the pictures on, I'll stick with the TV mix as it fits better with the pictures (and is almost in sync with them.)
EricLast edited by OldTechie; 12-08-12, 19:15. Reason: Why do I only see my typos after I press the submit button?Comment
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