Re: Podcast sample rate

[Jim web]

In article <27226B7FFE4A4AD99816CD3888598069@RJCDESK>, RS
 wrote:

> That was an aside.  My original question was why the BBC was using a
> 44.1kHz sampling rate for its podcasts (which are MP3) instead of
> standardising on 48kHz throughout.  Dave Lambley thought the reason
> might be that the LAME encoder had been tuned for a 44.1kHz sample
> rate.  There are certainly posts in hydrogenaudio which support that. 
> One on the dbpoweramp forum said there were dire consequences of
> encoding a 48kHz sample rate as 320kbit/s MP3.
> https://forum.dbpoweramp.com/showthread.php?14876-terrible-sound-quality-with-lame-mp3-48Khz

Apologies that I've not yet followed this up. As things stand I remain
puzzled by why the BBC do this as it isn't what I'd have expected! 

Afraid I've been distracted by something rather OT which is meaning I'm
spending lots of time burrowing though ancient notebooks, photos, etc... 
but I can't resist mentioning in passing now. :-) I'm in the process of
writing a sort of 'working history' which is appearing (slowly) at

http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html

Currently going through Hawai'i and UKIRT photos to work out when each of
them was taken for the next page(s).

However I'll email someone I know in case they can find say why the BBC
have been doing podcasts in this way. I'd not noticed because I've never
used the podcasts.

Jim

-- 
Electronics  https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html


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Re: Podcast sample rate

[RS]

From: Vangelis forthnet Sent: Monday, July 17, 2017 21:24


... If you are referring to the original *low radiomodes as fetched by GiP, 
then, and someone correct me, please, if I'm wrong, I believe 48.0kHz SR 
applies to hardware/software media players which are capable of reproducing 
the SBR portion of the HE-AACv1 encode; for SBR incompatible players, only 
the LC portion is played back at half the SR, i.e. 24.0kHz (resulting in 
most higher frequencies of the spectum being muted...).


Thanks for that, Vangelis.  I have just found this in Wikipedia which 
confirms what you say.

https://en.wikipedia.org/wiki/High-Efficiency_Advanced_Audio_Coding
"MPEG-2 and MPEG-4 AAC LC decoders without SBR support will decode the AAC 
LC part of the audio, resulting in audio output with only half the sampling 
frequency, thereby reducing the audio bandwidth. This usually results in the 
high-end, or treble, portion of the audio signal missing from the audio 
product."


That is something I didn't know.  It would seem that for many players there 
is a heavy penalty in using AAC with bitrates below hlsaacstd, dafstd and 
hafstd, because the *med and *low modes use SBR.


That was an aside.  My original question was why the BBC was using a 44.1kHz 
sampling rate for its podcasts (which are MP3) instead of standardising on 
48kHz throughout.  Dave Lambley thought the reason might be that the LAME 
encoder had been tuned for a 44.1kHz sample rate.  There are certainly posts 
in hydrogenaudio which support that.  One on the dbpoweramp forum said there 
were dire consequences of encoding a 48kHz sample rate as 320kbit/s MP3.

https://forum.dbpoweramp.com/showthread.php?14876-terrible-sound-quality-with-lame-mp3-48Khz

All those posts are 10 to 14 years old, so I don't know if they still apply. 
There is no mention of it on the Wikipedia and Sourceforge LAME pages.

https://en.wikipedia.org/wiki/LAME
http://lame.sourceforge.net/about.php




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