On 17 July 2017 at 17:32, RS <richard...@zoho.com> wrote: >> 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.
Surely a Nyquist frequency of 24kHz for a 48kHz sample rate? I don't remember where I heard the "stick to 44.1" lore from, but Google has turned up https://hydrogenaud.io/index.php/topic,9105.0.html Yes, I'd have thought that any problems relating to tuning would related to the psycho-acoustic stuff, and so would vanish given a high enough bit rate. >> 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. I can't answer that as the phone sadly died. The files would have been from get_iplayer in ~2010. Dave _______________________________________________ get_iplayer mailing list get_iplayer@lists.infradead.org http://lists.infradead.org/mailman/listinfo/get_iplayer
