Podcast sample rate

[RS]

>From: Dave Lambley
>Sent: Monday, July 17, 2017 15:43

>There are also CODEC internals to consider. The LAME people used to
>recommend resampling down to 44.1kHz before encoding, because that was
>the sample rate they had done most of their tuning against.

I didn't know about that recommendation and it may be what has influenced 
the BBC.  I have transcoded a fair number of 48kHz sample rate AAC files to 
MP3 using LAME with no audible problems.  That has mainly been at 128kbit/s. 
Maybe problems occur at lower bit rates.  At 48kbit/s Mediainfo shows the 
sampling rate as 48.0kHz / 24.0kHz.  I guess that means a Nyquist frequency 
of 12kHz.  Moneybox used to use a very low rate for its podcast.  I think it 
may have been a sample rate of 16kHz and a bit rate of 32kbit/s.

>For playback, 48kHz files are relatively rare outside video, and receive
>less testing.

A lot of audio is distributed on CD and of course the CD sampling rate is 
44.1kHz.

>My old Sony Ericsson phone, for example, would play back
>48kHz AAC with periodic digital splats.

Was that a 48kHz problem or an AAC problem?  Some players are very fussy 
about the AAC they will play.  I used to have a DAB+ radio which would also 
record DAB+ stations in AAC.  It was a struggle to find a DAB+ station but I 
found one in Poland.  Playback of its own AAC recordings was fine.  It was 
also fine playng MP3 files from its microSD card.  When it played external 
AAC files there was warbling sound over the top.