Sampling frequency on Radio programmes
northmedia1 at the.forthnet.gr
Sun Apr 26 06:17:57 PDT 2015
On Sun Apr 19 12:23:59 BST 2015, Jim web wrote:
> Longer answer:
> The background is more complex.
As others have already said so,
many (belated) thanks for the elaborate
> When I first started testing and experimenting with using get-iplayer
> some months ago, it was when the Coyopa system was running.
> And files obtained with get-iplayer were 44.1k.
> But when the main switchover was made, these
> changed to 48k and have remained so since.
> Again, talking to BBC contacts, this seems to be because
> get-iplayer was previously getting the 'pre-converted 44.1k files'
> that Coyopa was creating to send out to avoid the old Flash limit.
> Now that conversion isn't being done.
> All the files are 48k.
This is indeed true for the AdobeHDS, AppleHLS Listen Live
streams & the AppleHLS, RTMP AOD streams; all these have
now a sample rate (SR) of 48.0kHz.
However, one thing the "Audio Factory" people did was to kill
the ShoutcastAAC streams (with no prior notice), causing major
grief to owners of Internet Devices (mainly radios & "smart" TVs
/ BluRay players). This move complemented the scheduled demise
of the WMA Live/AOD streams...
As an interim solution, the AF team replaced the killed live streams
with ShoutcastMP3 ones.
These, again, target Internet Devices, but you can listen to them
in the software player of your choice that supports Shoutcast
(listening to R1 at the moment:
These live ShoutcastMP3 streams have a SR of just 44.1kHz,
so downsampling takes place along the line - I can't tell
if it's done in-house at the BBC prior to sending them to
the Limecast server or whether the server itself is configured
to downsample on-the-fly (?). Do you (or your contacts)
happen to know why this downsampling is needed/performed?
These streams are not meant for browsers, so surely the
Flash plugin should've nothing to do with it, really (???)
Is it possibly a limitation of the icy protocol?
FWIW, you can record the live ShoutcastMP3 streams
with GiP 2.92 like that:
get_iplayer --type=liveradio --pid=bbc_radio_one --modes=shoutcastmp3std2 --force
(this dumps 2min worth of live stream).
And I can't legally access the briefly re-instated ShoutcastAAC R3 stream,
get_iplayer --type=liveradio --pid=bbc_radio_three --modes=shoutcastaac --force
(geo-restricted to UK-only),
but this is 48.0 kHz, so it appears only the ShoutcastMP3 ones are 44.1 kHz
Hoping you can shed some more light into this...
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