Re: Podcast sample rate

[Jeremy Nicoll - ml gip]

On 2017-07-27 17:39, RS wrote:


Yes I do mean portable or MP3 players.  Thanks for the suggestion but
the Amazon description of the Fii0 X1 is a good example of what I have
been up against.  There is no indication in it of which file formats
the device supports.


But there is info on Fii0's website, though whether it's detailed enough
for you I have no idea.  See

 http://www.fiio.net/en/products/18/parameters

--
Jeremy Nicoll - my opinions are my own

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Re: Podcast sample rate

[michael norman]

On 27/07/17 17:39, RS wrote:

From: michael norman Sent: Wednesday, July 26, 2017 13:37


I have always used hardware players by which I assume you mean 
portable players to listen to music.  Those used to be called mp3 
players culminating in the iPOD I suppose.  Nowadays I still do that 
and having used various Cowon models in the past I now use a Fii0 X1.


Yes I do mean portable or MP3 players.  Thanks for the suggestion but 
the Amazon description of the Fii0 X1 is a good example of what I have 
been up against.  There is no indication in it of which file formats the 
device supports.


The X1 plays anything I can throw at it, see this review

https://www.cnet.com/uk/news/fiio-x1-finally-a-high-resolution-music-player-that-wont-empty-your-bank-account/

Before that I used Cowon players that did pretty much the same thing but 
didn't play hi res files, but I don't have any of those.  I have never 
used Sandisk models. but I have never had a problem playing MP3 files on 
the devices I've used.  If players purport to play AAC files and don't 
then that is surely something the buyer should take up with whoever 
supplied the device.  I read the exchanges about the Linn player, which 
like all Linn stuff costs big money, certainly more money than I've ever 
had, and I have lusted after Linn stuff for a long time, whether the guy 
who posted that issue got a satisfactory response from Linn I can't 
remember.


You want to play FLAC and OGG files from ripped CDs.  Several of the 
cheap players will play FLAC and OGG without problem.  I want mainly to 
play speech radio programmes from the BBC.  Some are available as MP3 
podcasts, but most are delivered by get_iplayer as AAC .  That is why I 
find it frustrating when players claim to support AAC-LC but don't or 
don't properly.  It is not a question of price.  One person had a 
problem playing long AAC files with a Linn player, and I gather they 
sell for several thousand pounds.  The SanDisk Clip Jam has come down in 
price and is now about £25.  I have been very lucky in that SanDisk 
support has fixed the problem I had with AAC within about two months.


I thought my satellite receiver played AAC-LC files without problem.  I 
have just discovered that although it does start to play them it stops 
at a point which is repeatable for each file but is very different from 
one file to another.  For example the 320kbit/s Radio 3 recording of 
Prom 3, which includes the Schumann 2nd symphony you referred to, stops 
at 41min 27s.  The 128kbit/s recording of the same Prom stops at 6min 31s.


It is not difficult to convert files to MP3, and MP3 has lot going for 
it, especially in terms of compatibility.  Quality from the latest LAME 
encoder is not far below AAC.  There are not many listening tests at 
high bit rates, but it is generally accepted that transparency, absence 
of audible artefacts no matter how difficult to encode the source 
material, is achieved with 256kbit/s AAC or 320kbit/s LAME MP3.


Yes it is quite possible to convert one lossy format to another I can do 
that quite easily, and yes LAME is as good as that as it gets.  I will 
not accept that encoding a lossless file into a lossy one does not 
involve a loss of quality, and lots of people agree with me.  But that's 
another debate.


The bigger question I suppose is how many devices can the BBC be 
expected to support on for their content.  Plus given that all of this 
is a moving target who if anybody could produce a list of which BBC 
modes work on which players ?  Or have I missed your point ?


There are extensions to AAC, called SBR and PS.  SBR is a more efficient 
way of encoding high frequencies.  As Vangelis has pointed out, if the 
player does not support SBR the high frequencies are lost.  PS is a 
different way of encoding stereo.  If the player does not support PS, 
all stereo information is lost.  10 years ago there was a need to reduce 
bit rates to save memory.  Players now have much larger memories.  I 
regard the extensions, together known as HE-AAC, as a retrograde step.  
They are not used at bit rates of 128kbit/s and above.  I would prefer 
the BBC always to make a mode of 128bit/s or higher available rather 
than use HE-AAC.


As for the types of devices supported by the BBC, having a large number 
is a good thing because it results in a wider choice of modes from 
get_iplayer.


SBR PS whatever, none of those can put back what is lost by encoding a 
file downwards, information is lost.


I don't do AAC, MP3 or whatever but the rest of the world does, so I 
imagine my point might be is the BBC output flawed in some way, assuming 
it isn't can the BBC be expected to make up for deficiencies in 
available players ?


M

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Re: Podcast sample rate

[RS]

From: michael norman Sent: Wednesday, July 26, 2017 13:37


I have always used hardware players by which I assume you mean portable 
players to listen to music.  Those used to be called mp3 players 
culminating in the iPOD I suppose.  Nowadays I still do that and having 
used various Cowon models in the past I now use a Fii0 X1.


Yes I do mean portable or MP3 players.  Thanks for the suggestion but the 
Amazon description of the Fii0 X1 is a good example of what I have been up 
against.  There is no indication in it of which file formats the device 
supports.


You want to play FLAC and OGG files from ripped CDs.  Several of the cheap 
players will play FLAC and OGG without problem.  I want mainly to play 
speech radio programmes from the BBC.  Some are available as MP3 podcasts, 
but most are delivered by get_iplayer as AAC .  That is why I find it 
frustrating when players claim to support AAC-LC but don't or don't 
properly.  It is not a question of price.  One person had a problem playing 
long AAC files with a Linn player, and I gather they sell for several 
thousand pounds.  The SanDisk Clip Jam has come down in price and is now 
about £25.  I have been very lucky in that SanDisk support has fixed the 
problem I had with AAC within about two months.


I thought my satellite receiver played AAC-LC files without problem.  I have 
just discovered that although it does start to play them it stops at a point 
which is repeatable for each file but is very different from one file to 
another.  For example the 320kbit/s Radio 3 recording of Prom 3, which 
includes the Schumann 2nd symphony you referred to, stops at 41min 27s.  The 
128kbit/s recording of the same Prom stops at 6min 31s.


It is not difficult to convert files to MP3, and MP3 has lot going for it, 
especially in terms of compatibility.  Quality from the latest LAME encoder 
is not far below AAC.  There are not many listening tests at high bit rates, 
but it is generally accepted that transparency, absence of audible artefacts 
no matter how difficult to encode the source material, is achieved with 
256kbit/s AAC or 320kbit/s LAME MP3.


The bigger question I suppose is how many devices can the BBC be expected 
to support on for their content.  Plus given that all of this is a moving 
target who if anybody could produce a list of which BBC modes work on which 
players ?  Or have I missed your point ?


There are extensions to AAC, called SBR and PS.  SBR is a more efficient way 
of encoding high frequencies.  As Vangelis has pointed out, if the player 
does not support SBR the high frequencies are lost.  PS is a different way 
of encoding stereo.  If the player does not support PS, all stereo 
information is lost.  10 years ago there was a need to reduce bit rates to 
save memory.  Players now have much larger memories.  I regard the 
extensions, together known as HE-AAC, as a retrograde step.  They are not 
used at bit rates of 128kbit/s and above.  I would prefer the BBC always to 
make a mode of 128bit/s or higher available rather than use HE-AAC.


As for the types of devices supported by the BBC, having a large number is a 
good thing because it results in a wider choice of modes from get_iplayer.





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Re: Podcast sample rate

[RS]

From: Jim web
Sent: Wednesday, July 26, 2017 13:12



WRT TV I think the Proms files I've fetched are all 320k audio now. But
I've not checked in detail what I've got thus far. My personal regret here
is that I'd prefer the 25fps video with 320k audio, but have to go for
50fps to get it.


I think you're right about 320kbit/s audio only being with the 50fps modes. 
25fps HVFxsd only has 96kbit/s HE-AAC v1 with SBR.  HLShd has 96kbit/s 
AAC-LC.  I guess it would not be too difficult to take the video stream from 
HLShd and multiplex it with the audio stream from HVFsd.  On the .ts files 
Mediainfo shows the audio delay.  On one I looked at it was only 20ms or 
half a frame, which is not worth worrying about.


For the first time I downloaded HVFsd to get the 320kbit/s audio and played 
it back in VLC on this machine.  The picture quality was atrocious.  Bernard 
Haitink moved fairly smoothly but panning over the orchestra was very jerky 
at about 5fps.  HVFhd was even worse.  The screen went grey from time to 
time with interruptions to the audio.  This is an elderly machine with a 
2.33GHz Core 2 Duo and 4GByte of RAM.  I do have faster laptops with 8GByte 
of RAM.  I'll have to see what happens on them.   I also have a netbook with 
a 1.66GHz Atom which struggles with 832x460 25fps.  I wonder if the BBC took 
it into account when it decided Video Factory would standardise on 960x540 
50fps.  Fortunately my satellite receiver plays the files.



FWIW I've not fetched any 320k radio files of Proms yet this year. Too
busy with the flac! :-)


I'll have to look back at your notes on how to get FLAC.





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Re: Podcast sample rate

[michael norman]

On 26/07/17 12:36, RS wrote:

Sent: Thursday, July 20, 2017 12:56  I wrote

To: get_iplayer@lists.infradead.org
Subject: Re: Podcast sample rate

I wish the BBC would think more about backwards compatibility of AAC. 
There is no problem with software players.  HTML5 and recent versions 
of VLC fully support HE-AAC v2 with LC (Low Complexity), SBR (Spectral 
Band Replication) and PS (Parametric Stereo).  The problem is with 
hardware players.


I am not alone in this list in having had difficulties playing AAC-LC 
at all.  When trying to find hardware players which support SBR and PS 
the problem gets worse.


I have always used hardware players by which I assume you mean portable 
players to listen to music.  Those used to be called mp3 players 
culminating in the iPOD I suppose.  Nowadays I still do that and having 
used various Cowon models in the past I now use a Fii0 X1.  That one 
costs around £99 plus memory card.  Nowadays I imagine most people use 
smartphones as general media devices and the market such as it is for 
"mp3 players" has moved upmarket into its own niche.  My Fiio device is 
one of the cheapest options in that market.  I only use it to play cds 
ripped into flac or ogg and a very few mp3  I imagine if I put a some 
radio programmes from GIP on it that it "should" play them, I haven't 
tried that.  Whether cheaper players like some on the Sandisk ones that 
will do that I don't know.  Neither do I know how smartphones perform in 
this area for the simple reason that I don't have one.


The bigger question I suppose is how many devices can the BBC be 
expected to support on for their content.  Plus given that all of this 
is a moving target who if anybody could produce a list of which BBC 
modes work on which players ?  Or have I missed your point ?


Obviously what I would like the BBC to do is off topic.  Even so, I hope 
I will be forgiven for saying that I would like to see a move towards at 
least 128kbit/s stereo audio in preference to adding SBR.


I only have a vague idea of what SBR or even VBR means. is that an MP3 
thing ? I only use MP3 when I can't get the content any other way.


What I would like get_iplayer to do is to include in the documentation a 
warning of the perils of SBR for players which do not support it and to 
include in the table in

https://github.com/get-iplayer/get_iplayer/wiki/modesref
an indication of which modes use SBR and which do not.


A question for the GIP developers ?


Is the table up to date?  For HVF 50fps modes it shows the audio bit 
rate as 128kbit/s or 320kbit/s and for HVF 25fps modes other than HVFlow 
it shows the audio bit rate as 96kbit/s or 320kbit/s.  I have not used 
the 50fps modes but I have occasionally used HVFxsd.  I have not seen 
320kbit/s audio. Which programmes use it?


See last coment.


Is the radio table up to date?  I thought I had seen somewhere that 
there had been a relaxation of the 96kbit/s maximum bit rate when 
listening abroad.  I can't find anything about it on the BBC's website.  
This page

https://www.bbc.co.uk/iplayer/help/Mobile_abroad
tells me under the heading, "Can I listen to radio abroad?"
"You can also listen to BBC radio outside the UK from a desktop computer 
at www.bbc.co.uk/radio."
There is no mention of bit rate.  If I go to that page in Firefox it 
does indeed play the programme I select, but it does not offer me a 
choice of bit rates, but automatically plays at 320kbit/s.  I have not 
tried doing it abroad.


Interestingly that 320kbit/s bit rate means the radio iPlayer offers the 
highest bit rate of any mode of delivering radio programmes.  Television 
is the poor relation in comparison.  Many broadcast programmes include a 
256kbit/s AC3 stream, but for most modes the iPlayer does not offer 
anything better than 96kbit/s stereo.


Listening abroad is not an issue for me, being in UK

For my use radio downloads are now 320kbits by default which suits me 
given thar I have the bandwidth, I assume I could specify a different 
mode if I needed to.


As you say if you listen to radio iPlayer via Firefox or any other 
browser it doesn't offer a choice of bitrates.  I think it should but 
maybe that's one for the BBC.


Personally I'd like to see tv programmes offer the highest quality audio 
as per radio, again one for the BBC ?



M

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Re: Podcast sample rate

[michael norman]

On 26/07/17 13:12, Jim web wrote:

In article , RS
 wrote:

There is no mention of bit rate.  If I go to that page in Firefox it
does indeed play the programme I select, but it does not offer me a
choice of bit rates, but automatically plays at 320kbit/s.  I have not
tried doing it abroad.


IIRC the standard iplayer radio interface is 'adaptive' and tries to send
the highest rate the connection, method, and software shows it can deliver
to the client. So you should get 320k *unless* that seems not to work, or
something can't cope, when it may drop to trying a lower rate.

WRT TV I think the Proms files I've fetched are all 320k audio now. But
I've not checked in detail what I've got thus far. My personal regret here
is that I'd prefer the 25fps video with 320k audio, but have to go for
50fps to get it.

FWIW I've not fetched any 320k radio files of Proms yet this year. Too
busy with the flac! :-)

Jim


Jim

Proms ain't really my thing but I just downloaded the radio Barenboim 
Elgar one at 320k.  Plays very nicely here via VLC.


But you probably knew that.

Lovely music.

M

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Re: Podcast sample rate

[Jim web]

In article , RS
 wrote:
> There is no mention of bit rate.  If I go to that page in Firefox it
> does indeed play the programme I select, but it does not offer me a
> choice of bit rates, but automatically plays at 320kbit/s.  I have not
> tried doing it abroad.

IIRC the standard iplayer radio interface is 'adaptive' and tries to send
the highest rate the connection, method, and software shows it can deliver
to the client. So you should get 320k *unless* that seems not to work, or
something can't cope, when it may drop to trying a lower rate.

WRT TV I think the Proms files I've fetched are all 320k audio now. But
I've not checked in detail what I've got thus far. My personal regret here
is that I'd prefer the 25fps video with 320k audio, but have to go for
50fps to get it.

FWIW I've not fetched any 320k radio files of Proms yet this year. Too
busy with the flac! :-)

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]

Sent: Thursday, July 20, 2017 12:56  I wrote

To: get_iplayer@lists.infradead.org
Subject: Re: Podcast sample rate

I wish the BBC would think more about backwards compatibility of AAC. 
There is no problem with software players.  HTML5 and recent versions of 
VLC fully support HE-AAC v2 with LC (Low Complexity), SBR (Spectral Band 
Replication) and PS (Parametric Stereo).  The problem is with hardware 
players.


I am not alone in this list in having had difficulties playing AAC-LC at 
all.  When trying to find hardware players which support SBR and PS the 
problem gets worse.


Obviously what I would like the BBC to do is off topic.  Even so, I hope I 
will be forgiven for saying that I would like to see a move towards at least 
128kbit/s stereo audio in preference to adding SBR.


What I would like get_iplayer to do is to include in the documentation a 
warning of the perils of SBR for players which do not support it and to 
include in the table in

https://github.com/get-iplayer/get_iplayer/wiki/modesref
an indication of which modes use SBR and which do not.

Is the table up to date?  For HVF 50fps modes it shows the audio bit rate as 
128kbit/s or 320kbit/s and for HVF 25fps modes other than HVFlow it shows 
the audio bit rate as 96kbit/s or 320kbit/s.  I have not used the 50fps 
modes but I have occasionally used HVFxsd.  I have not seen 320kbit/s audio. 
Which programmes use it?


Is the radio table up to date?  I thought I had seen somewhere that there 
had been a relaxation of the 96kbit/s maximum bit rate when listening 
abroad.  I can't find anything about it on the BBC's website.  This page

https://www.bbc.co.uk/iplayer/help/Mobile_abroad
tells me under the heading, "Can I listen to radio abroad?"
"You can also listen to BBC radio outside the UK from a desktop computer at 
www.bbc.co.uk/radio."
There is no mention of bit rate.  If I go to that page in Firefox it does 
indeed play the programme I select, but it does not offer me a choice of bit 
rates, but automatically plays at 320kbit/s.  I have not tried doing it 
abroad.


Interestingly that 320kbit/s bit rate means the radio iPlayer offers the 
highest bit rate of any mode of delivering radio programmes.  Television is 
the poor relation in comparison.  Many broadcast programmes include a 
256kbit/s AC3 stream, but for most modes the iPlayer does not offer anything 
better than 96kbit/s stereo.




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Re: Podcast sample rate

[Jim web]

I've just been told unofficially that this is a 'legacy' issue. i.e. to
ensure that as many types of device as possible can play them, even ancient
kit.

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

[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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Re: Podcast sample rate

[Vangelis forthnet]

On Mon Jul 17 17:32:03 BST 2017, RS wrote: 

At 48kbit/s Mediainfo shows the 
sampling rate as 48.0kHz / 24.0kHz.


... 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...). 
If I have misunderstood and you're referring to 
something else, please disregard and accept my apologies :-)


Vangelis.

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Re: Podcast sample rate

[Dave Lambley]

On 17 July 2017 at 17:32, RS  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

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Re: Podcast sample rate

[Christopher Woods]

As far as I'm aware, the BBC's audio estate runs at 48 KHz (well, except 
the Archers studio - and probably a handful of other studios - for legacy 
purposes).


Looks like podcasts are still encoded to 44.1 KHz via iBroadcast (the MP3s' 
encoder tag indicates ffmpeg (currently Lavc57.24)). Except where a podcast 
is generated programmatically from a broadcast programme (e.g. World at One 
on Radio 4), the podcast guide instructs to upload WAVs directly to 
iBroadcast. I suppose it must still have a separate encode and publish 
workflow from Audio Factory.


(I don't have anything to do with podcasts, mind...)

Years ago when they started, 44.1 was part of the defined spec for BBC 
podcasts and I presume nobody's ever really cared enough to change it. I'm 
listening to one at the moment and its audio quality is perfect fine.


iPlayer audio is provided / encoded through a different process so will be 
48, and also a higher bit rate (and AAC). Podcasts were designed to be 
listened to on average earbuds while on the go and have to remain 
compatible with devices potentially over a decade old. So, er, go figure.




On 17 July 2017 3:44:31 p.m. "RS"  wrote:


From: Jim web
Sent: Monday, July 17, 2017 14:05



In fact every BBC podcast I have seen, admittedly a tiny sample of the
population of podcasts, has used a 44.1kHz sample rate.



Are there are recent examples I could get using GiP?


I have a feeling that GiP support for podcasts has been withdrawn, but here
are four recent examples which you can download directly.

http://open.live.bbc.co.uk/mediaselector/5/redir/version/2.0/mediaset/audio-nondrm-download/proto/http/vpid/p058rwkw.mp3

http://open.live.bbc.co.uk/mediaselector/5/redir/version/2.0/mediaset/audio-nondrm-download/proto/http/vpid/p057xbn0.mp3

http://open.live.bbc.co.uk/mediaselector/5/redir/version/2.0/mediaset/audio-nondrm-download/proto/http/vpid/p058pxd2.mp3

http://open.live.bbc.co.uk/mediaselector/5/redir/version/2.0/mediaset/audio-nondrm-download/proto/http/vpid/p058rm6r.mp3

Three of them are Radio 4 and one Radio 3.  If you download the .m4a files
using GiP and the following PIDs the sample rate is 48kHz, so the BBC is
using both, which seems crazy.

b08xx96m
b08xcqwf
b08wr7ss
b08xcwz4




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Re: Podcast sample rate

[RS]

From: Jim web
Sent: Monday, July 17, 2017 14:05



In fact every BBC podcast I have seen, admittedly a tiny sample of the
population of podcasts, has used a 44.1kHz sample rate.



Are there are recent examples I could get using GiP?


I have a feeling that GiP support for podcasts has been withdrawn, but here 
are four recent examples which you can download directly.


http://open.live.bbc.co.uk/mediaselector/5/redir/version/2.0/mediaset/audio-nondrm-download/proto/http/vpid/p058rwkw.mp3

http://open.live.bbc.co.uk/mediaselector/5/redir/version/2.0/mediaset/audio-nondrm-download/proto/http/vpid/p057xbn0.mp3

http://open.live.bbc.co.uk/mediaselector/5/redir/version/2.0/mediaset/audio-nondrm-download/proto/http/vpid/p058pxd2.mp3

http://open.live.bbc.co.uk/mediaselector/5/redir/version/2.0/mediaset/audio-nondrm-download/proto/http/vpid/p058rm6r.mp3

Three of them are Radio 4 and one Radio 3.  If you download the .m4a files 
using GiP and the following PIDs the sample rate is 48kHz, so the BBC is 
using both, which seems crazy.


b08xx96m
b08xcqwf
b08wr7ss
b08xcwz4




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Re: Podcast sample rate

[Dave Lambley]

On 17 July 2017 at 14:05, Jim web  wrote:
> The main problem with 48k -> 44.1k resampling is that it will risk adding
> artifacts. If you're wanting to save bits it would make more sense to tell
> a lossy encoder to simply ignore anything above a given HF limit. (Various
> BBC outlets used to do this some years ago.) The result can then remain 48k
> rate but have the allocated bits used for more detail at lower frequencies.

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. For
playback, 48kHz files are relatively rare outside video, and receive
less testing. My old Sony Ericsson phone, for example, would play back
48kHz AAC with periodic digital splats.

Dave

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Re: Podcast sample rate

[Jim web]

In article , RS
 wrote:
> Vangelis's mention of podcasts has reminded me of another comment I was
> going to make.  A long time ago someone, it may have been Jim, took me
> to task for referring to a 44.1kHz sample rate.  He said it must have
> been a very old file, because the BBC had standardised on a 48kHz
> sample rate.

Afraid I can't recall that. But then my memory is lousy! :-)

> In fact every BBC podcast I have seen, admittedly a tiny sample of the
> population of podcasts, has used a 44.1kHz sample rate.

Are there are recent examples I could get using GiP?

What I know I've said is that the BBC have standardised on 48k. But this is
for their own internal working and for most output - e.g. TV, DAB, and
standard iplayer, etc. There *are* exceptions - e.g. FM Radio distribution
which is 32k, but the public won't have direct access to that. Legacy
problem.

'Podcasts' might for all I know be done by a programme producer. And they
in their infinite wisdom might resample to another rate.


> I read a forum post, probably in something like hydrogenaudio, where
> someone said he resampled everything to 48kHz because the convenience
> of having everything at the same sample rate outweighed a tiny increase
> in quantising noise.  (I worked it out once.  I think for 16 bit linear
> encoding it is about -95dB.)   I can't understand the rationale of
> going the other way. To resample everything that is going to be used as
> a podcast at 44.1kHz seems a huge waste of effort.

The main problem with 48k -> 44.1k resampling is that it will risk adding
artifacts. If you're wanting to save bits it would make more sense to tell
a lossy encoder to simply ignore anything above a given HF limit. (Various
BBC outlets used to do this some years ago.) The result can then remain 48k
rate but have the allocated bits used for more detail at lower frequencies.

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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Podcast sample rate

[RS]

Vangelis's mention of podcasts has reminded me of another comment I was 
going to make.  A long time ago someone, it may have been Jim, took me to 
task for referring to a 44.1kHz sample rate.  He said it must have been a 
very old file, because the BBC had standardised on a 48kHz sample rate.


In fact every BBC podcast I have seen, admittedly a tiny sample of the 
population of podcasts, has used a 44.1kHz sample rate.


I read a forum post, probably in something like hydrogenaudio, where someone 
said he resampled everything to 48kHz because the convenience of having 
everything at the same sample rate outweighed a tiny increase in quantising 
noise.  (I worked it out once.  I think for 16 bit linear encoding it is 
about -95dB.)   I can't understand the rationale of going the other way. 
To resample everything that is going to be used as a podcast at 44.1kHz 
seems a huge waste of effort.




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