#276921 - 06/03/2006 23:04
Aux in recording XM source
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new poster
Registered: 04/04/2004
Posts: 16
Loc: Midwest
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Been searching for this, Rio.org FAQ's say while this is theoretically possible it is unlikely to ever be implemented. I understand this but since then has anybody done it?
I'd like to record jokes I hear on the comedy channels on my XM satellite so I may remember them later & not sound like I'm remembering them as I tell it, which I am, but what a pain it is to listen to & tell.
I realize the player is a player and not a recorder & the drives would be required to be read-write. My guess is that monitoring the amount of HDD usage, disk space remaining, would be a factor as well. I wouldn't need a quality recording just clear enough to hear again later & undertand it. It wouldn't necessarily have to work when the XM is still playing which I understand would make it easier. Anything like that been done?
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#276924 - 05/06/2007 12:19
Re: Aux in recording XM source
[Re: Snowshoe]
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enthusiast
Registered: 04/02/2002
Posts: 277
Loc: Massachussetts
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This would be amazing...
You are listening to a "live" source through the aux in
like the radio and you want to pause what you are hearing
like you normally do when listening to mp3 playback...
Just hit the "up" button...
Audio is muted and the empeg starts recording.....
Un pause and pick back up where you were...
if you come accross a commercial that was recorded while paused...
just fast forward a la tivo dvr.
I don't beleive that that the audio stream could be recorded in mp3 format,
compression of mp3 could be slower than real time.
but even a medium quailty wav audio format would be great.
I am in no way qulified to even know where to start on this software
but it sounds like a simple enough application.
you'd need some read write disk space...
oops, is there sufficient hardware on board an empeg to actually record an audio stream...?
<brain explodes>
any one else?
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davecosta
Hijacked 60GB MKIIa 2.0b13
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#276925 - 05/06/2007 13:40
Re: Aux in recording XM source
[Re: dcosta]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Buffering more than a minute or two of stuff would require the hard drive for buffer space,
which means it would then remain spun up for the duration, or at least until one's
listening catches up to "real time" again.
The drives will thus overheat (the cooling within the empeg is insufficient to handle
drives that spin continuously), so you'll want to combine your software with a fan
to keep things from melting down.
The cs4231a chip can sample from aux-in --> that's how the aux-in visuals are done.
Whether or not it can sample at sufficient quality for playback is another matter.
EDIT: An equally big question is, can it sample Aux-in while we play sound
from software, or is sampling of aux-in only possible when aux-in is being played out?
Cheers
Edited by mlord (05/06/2007 13:41)
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#276926 - 05/06/2007 15:13
Re: Aux in recording XM source
[Re: mlord]
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carpal tunnel
Registered: 20/12/1999
Posts: 31600
Loc: Seattle, WA
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Quote:
EDIT: An equally big question is, can it sample Aux-in while we play sound
from software, or is sampling of aux-in only possible when aux-in is being played out?
When this discussion first came up (and the FAQ entry was written), my understanding was "no". I could be wrong about it, there are a lot of complexities surrounding this.
Quote:
The cs4231a chip can sample from aux-in --> that's how the aux-in visuals are done.
Whether or not it can sample at sufficient quality for playback is another matter.
My understanding (again, a vague one) was that the sampling would max out at some low frequency, such as 7k or something. I don't remember the exact number.
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#276927 - 05/06/2007 16:24
Re: Aux in recording XM source
[Re: tfabris]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Quote:
Quote:
EDIT: An equally big question is, can it sample Aux-in while we play sound
from software, or is sampling of aux-in only possible when aux-in is being played out?
When this discussion first came up (and the FAQ entry was written), my understanding was "no". I could be wrong about it, there are a lot of complexities surrounding this.
Well, tracing around a mk2a board, it appears that the cs4231a can sample from AUX-IN independently of whatever source is actually playing via the DSP.
Quote:
Quote:
The cs4231a chip can sample from aux-in --> that's how the aux-in visuals are done.
Whether or not it can sample at sufficient quality for playback is another matter.
My understanding (again, a vague one) was that the sampling would max out at some low frequency, such as 7k or something. I don't remember the exact number.
The cs4231a documentation indicates that it can collect stereo 16-bit samples at various rates, including 48.0KHz and 44.1KHz (CD audio), depending upon the crystals/clocks it has been wired up with. I haven't bothered hooking up the LogicPort to measure those, but I don't think sample rate will be an issue for the hardware.
Cheers
Edited by mlord (05/06/2007 16:27)
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#276928 - 05/06/2007 16:28
Re: Aux in recording XM source
[Re: mlord]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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We also have this note from Hugo, in the kernel source code: Quote:
* The Crystal CS4231A is used for input from the microphone on the empeg
* board (rev6+). This is a soundblaster-like type thing, with 16-bit audio
* I/O and an ISA-style interface.
*
* It's hooked up to the outputs of the DSP (so we can sample anything the DSP
* is outputting - eg for doing visuals on the radio or aux inputs), to the
* mono microphone input, and to the aux inputs (allowing us to sample the aux
* in even when playing other things through the DSP).
Edited by mlord (05/06/2007 16:34)
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#276929 - 05/06/2007 16:32
Re: Aux in recording XM source
[Re: mlord]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Also from the source code, the kernel device driver for the cs4231a is currently set up for a choice of three sample rates: Quote:
static struct { short samplerate; char setup; } samplerates[]={
{ 11025, 0x0d },
{ 22050, 0x0c },
{ 29400, 0x0a },
{ 0, 0 } };
The usual rate used for visuals is 29.4KHz, Stereo, 16-bits/channel.
Not quite CD-Audio, but sufficiently good for high-quality radio in an automobile.
I don't know if there's a hardware crystal/clock limit that prevents even
better rates or not, but that should be simple enough to determine from
anyone with schematics, or from tracing signals on the PCB.
Cheers
Edited by mlord (05/06/2007 16:33)
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#276931 - 05/06/2007 17:58
Re: Aux in recording XM source
[Re: mlord]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Quote:
Also from the source code, the kernel device driver for the cs4231a is currently
set up for a choice of three sample rates:
Quote:
static struct { short samplerate; char setup; } samplerates[]={
{ 11025, 0x0d },
{ 22050, 0x0c },
{ 29400, 0x0a },
{ 0, 0 } };
The usual rate used for visuals is 29.4KHz, Stereo, 16-bits/channel.
Not quite CD-Audio, but sufficiently good for high-quality radio in an automobile.
Working backwards from those three existing values, one determines that
the maximum possible sample rate with the existing empeg clock sources
is 29.4KHz (clock source 1), or 14.7KHz (clock source 2).
So that's the best it can do -- good enough, I think.
Cheers
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#276932 - 05/06/2007 23:38
Re: Aux in recording XM source
[Re: Snowshoe]
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pooh-bah
Registered: 19/09/2002
Posts: 2494
Loc: East Coast, USA
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But if you hear the joke and decide that it's funny and you want to record it, the joke is past. Can you rewind XM radio to go back and grab it?
Still, sounds like an interesting project. There are tons of times that I hear a song I don't know on college radio and I'd like to record a clip or record the announcer saying the title/artist/label. Sure beats trying to type it into my Treo as I drive. (should have bought voice memo recording software for it by now...)
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#276933 - 06/06/2007 22:28
Re: Aux in recording XM source
[Re: FireFox31]
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carpal tunnel
Registered: 10/06/1999
Posts: 5916
Loc: Wivenhoe, Essex, UK
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Quote:
But if you hear the joke and decide that it's funny and you want to record it, the joke is past. Can you rewind XM radio to go back and grab it?
The radio recording app would have to be constantly buffering the last few minutes of audio from the tuner, the same way TiVo and the other PVRs do with video. That would of course mean having the hard drive spun up the whole time, but if the hard drive in question was a CF card then that wouldn't matter. Constantly writing to a CF card raises other issues of course...
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