I've just installed Linux (Debian stable version) on an unused laptop I
had lying around (no mean feat considering I'm no computer or
engineering geek!) which I use to listen to Radio 3 through the BBC iPlayer.
Browser is Google Chrome.
The audio is streamed through the usb output into an M2Tech HiFace
digital audio interface and then onto a Cambridge Audio DacMagic.
Is there a simple way of measuring or even 'seeing' on the laptop the
frequency and bit rates which are being fed to the usb output from the
iPlayer?
I tried 'usbview' but to no luck. It didn't even detect the HiFace
interface.
Thanks.

--
Froggy

Baldrick: I've got this big growth in the middle of my face.
Blackadder: That's your nose, Baldrick.

(Blackadder the Third)

In article , froggy
wrote:
I've just installed Linux (Debian stable version) on an unused laptop I
had lying around (no mean feat considering I'm no computer or
engineering geek!) which I use to listen to Radio 3 through the BBC
iPlayer. Browser is Google Chrome. The audio is streamed through the usb
output into an M2Tech HiFace digital audio interface and then onto a
Cambridge Audio DacMagic. Is there a simple way of measuring or even
'seeing' on the laptop the frequency and bit rates which are being fed
to the usb output from the iPlayer?

Which of the indicator LEDs on the front of the DacMagic light up? That
should tell you the sample rate it is getting.

FWIW The BBC still use 44.1k sample rate. They have said they might go to
48k 'sometime' but I've not noticed a change as yet.

Or by 'bit rate' do you mean the AAC stream rate? If so, then that doesn't
appear outside their plugin with FireFox. No idea how Chrome handles it.
But the Linux *audio* system will presumably just handle the resulting
44.1k LPCM and have no idea of the AAC details.

The older versions of the BBC iPlayer used to show a rate in the Flash
plugin area. But then this ceased to be reliable as a guide as it was
pre-set, not actually detecting the rate. And now they've taken it away
entirely from their newer interfaces I think.

So to find out, use something like a system monitor to see the rate at
which data is arriving over the net. I use gnome-system-monitor on my
Xubuntu machines for this as it gives a total and a running graph. If you
time this you can get a decent idea of the average rate. For R3 it comes
out slightly about the actual AAC rate due to all the added 'overheads' of
the transfer processes.

You *should* get 320k AAC from the 'high' quality choice of R3 live. But
the 'listen again' tends to be lower rates like 192 or 128.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 20/03/13 14:23, froggy wrote:

I've just installed Linux (Debian stable version) on an unused laptop I
had lying around (no mean feat considering I'm no computer or
engineering geek!) which I use to listen to Radio 3 through the BBC iPlayer.
Browser is Google Chrome.
The audio is streamed through the usb output into an M2Tech HiFace
digital audio interface and then onto a Cambridge Audio DacMagic.
Is there a simple way of measuring or even 'seeing' on the laptop the
frequency and bit rates which are being fed to the usb output from the
iPlayer?
I tried 'usbview' but to no luck. It didn't even detect the HiFace
interface.

Did you not see this earlier in this newsgroup?

On 06/03/13 23:31, Andy Furniss wrote:

I don't know about USB, but for others you can see what is being fed
to the h/w by doing (while playing something) -

cat /proc/asound/card0/pcm0p/sub0/hw_params

Of course the numbers may need changing to suit setup.

You now have the chance to try that out on USB.

--
╔�╦�╦�����╦���╗
â•‘ â•‘ â•‘ â•‘ â•‘
╔�� ║ ║ ║ ║ ║ ╔��
╚���╩�╩�╩�╩�╩�� -- JimP.

In article , Jim Price
wrote:
On 20/03/13 14:23, froggy wrote:


On 06/03/13 23:31, Andy Furniss wrote:

I don't know about USB, but for others you can see what is being fed
to the h/w by doing (while playing something) -

cat /proc/asound/card0/pcm0p/sub0/hw_params

Of course the numbers may need changing to suit setup.

You now have the chance to try that out on USB.

I'm not clear what the OP actually means by 'rate' etc. The DAC Magic shows
the sample rate it is getting. It has a row of LEDs and the relevant one
lights up. And the iPlayer uses 44.1k sample rate.

The byte rate may be confusing as the USB interface may be shifting signed
intergers of the same size for both 24 and 16 bit samples from the source.
(The iPlayer is based on 16 bit samples, though.)

If he means the stream bitrate, then that won't show up at the level of the
ALSA output / transfers as the conversion to lpcm from AAC will have been
done by the browser or plugin.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Le 20/03/13 17:55, Jim Price a écrit :


Did you not see this earlier in this newsgroup?

On 06/03/13 23:31, Andy Furniss wrote:

I don't know about USB, but for others you can see what is being fed
to the h/w by doing (while playing something) -

cat /proc/asound/card0/pcm0p/sub0/hw_params

Of course the numbers may need changing to suit setup.

You now have the chance to try that out on USB.


Thanks for the tip.
I tried it out and got the following message:

access: MMAP_INTERLEAVED
format: S32_LE
subformat: STD
channels: 2
rate: 48000 (48000/1)
period_size: 1024
buffer_size: 4096

The 48000 figure obviously corresponds to the sample rate JL was
referring to. The fact that the 48k indicator light on the DacMagic lit
up seems to indicate that the BBC has increased the sample rate from
44.1k to 48K.


So to find out, use something like a system monitor to see the rate at
which data is arriving over the net. I use gnome-system-monitor on my
Xubuntu machines for this as it gives a total and a running graph. If you
time this you can get a decent idea of the average rate. For R3 it comes
out slightly about the actual AAC rate due to all the added 'overheads' of
the transfer processes.

You *should* get 320k AAC from the 'high' quality choice of R3 live. But
the 'listen again' tends to be lower rates like 192 or 128.

Slainte,

Jim


I hadn't thought of using the system monitor. Thanks for the tip Jim. I
got a reading of 300 to 390 kbps while listening to radio 3. Conclusion:
those of us who live abroad can still benefit from the full 320 kbps
Radio 3 stream on iPlayer.

Thank you all for your help.

--
Froggy

Baldrick: I've got this big growth in the middle of my face.
Blackadder: That's your nose, Baldrick.

(Blackadder the Third)

In article , froggy
wrote:
Le 20/03/13 17:55, Jim Price a écrit :


cat /proc/asound/card0/pcm0p/sub0/hw_params

Of course the numbers may need changing to suit setup.

You now have the chance to try that out on USB.


Thanks for the tip. I tried it out and got the following message:

access: MMAP_INTERLEAVED format: S32_LE subformat: STD channels: 2 rate:
48000 (48000/1) period_size: 1024 buffer_size: 4096

The 48000 figure obviously corresponds to the sample rate JL was
referring to. The fact that the 48k indicator light on the DacMagic lit
up seems to indicate that the BBC has increased the sample rate from
44.1k to 48K.

Not necessarily, I'm afraid.

I just checked, and here both

bbc.co.uk/iplayer/bbc_radio_three/listen_live

and

bbc.co.uk/player/bbc_radio_three

output 44.1k sample rates. (The second I only checked with 'hi' bandwidth
sic selected.)

(The above is using a Cambridge Audio 851C as the USB DAC. And I've set my
systems so the output rate automatically follows the source rate.)

You may find that something in your sound setup is 'mixing' for you,
without you knowing or approving. Pulse Audio has a habit of doing this,
but ALSA also may if the install assumes it is expected.

On computers 'mixing' is used so you can combine audio sources, ete. e.g.
Be able to hear a "mail's here!" noise whilst listening to music, or chat
over VOIP whilst listening to music. But it can interfere needlessly.

If you want to avoid this and have a direct output for best quality you may
find it useful to read the webpages I wrote on this topic. These advise
killing off Pulse Audio and having a simple file to tell the system exactly
what you require. The details are at:

http://www.audiomisc.co.uk/Linux/ALS...reSilence.html
http://www.audiomisc.co.uk/Linux/ALSA/ALSAforUsers.html

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html