ALSA for audio
 

On Sat, 16 Feb 2013 12:43:44 +0000 (GMT)
Jim Lesurf wrote:

In article , Davey
wrote:
On Fri, 15 Feb 2013 14:11:17 +0000 (GMT) Jim Lesurf
wrote:

arecord
Ok, here is what I found out. Bear in mind I have never used
arecord, only aplay. Both of my TV encoders work fine with their
respective WIN 7 programs, so that is how I use them, I never
succeeded in getting either of them to work with Linux. With a lot
more time, maybe I would be able to. Maybe. So, still in Ubuntu
10.04, I ran aplay -l and aplay -L, and arecord -l, and arecord -L,
before inserting the EZCap into a USB port.

A problem with this is that I have no real idea what "EZCap" is.
You'd have to say more about that.

It does the same job as a Hauppaugge TV tuner, with a USB connection.
Similar to a Dazzle. If you really need to know more, I can try, but
we'll stick with that for now.



aplay -L with the EZCap added the line:

iec958:CARD=U0xeb1a0x2861,DEV=0 USB Device 0xeb1a:0x2861, USB Audio
IEC958 (S/PDIF) Digital Audio Output

How does aplay -l list it? I'd have guessed from its name that it is a
'capture' device so wouldn't appear at all for aplay -l.


Correct.


arecord -l added:

card 2: U0xeb1a0x2861 [USB Device 0xeb1a:0x2861], device 0: USB
Audio [USB Audio] Subdevices: 1/1 Subdevice #0: subdevice #0

That says it is hw:2,0,0 for capture.


I managed to work that out, too. g

This sounds to me as though the device is being seen and recognised.
Volume Control Sound Preferences also shows it as: 2861 / 1 Input /
Analog Stereo Input, which is good.

What "Volume Control Sound Preferences" do you mean here? How are you
getting that info?


At least on my Ubuntu 10.04 installation, the volume icon in the upper
right has a 'Preferences' option on left-click along with the volume
slider. This leads to a set of dialog boxes, where I can gain access to
the various sound cards, to a limited extent only. The EZCap shows up
here, along with the Internal Card, and the HDMI card.

alsamixer shows one L R CAPTURE volume bar whether or not the
device is plugged in, so it is probably referring to an internal
device, such as the internal Intel soundcard. If so, where is the
USB device? I now need to work out what arecord instruction to give
to record something, but I need to do some reading for that. Just
tried a basic arecord, and whatever I do, it returns: arecord:
main:608: audio open error: No such file or directory

You'd need to say what you mean by a 'basic' arecord.

Try something like arecord -D plughw:2,0,0 -f dat -t wav -d 5 fred.wav

If it can find the device it should give you a five second long wave
file called fred.wav, stereo 48k rate. If not, say what errors it
returns.

It seems to record a file, but I cannot find any data when I play it! I
have 'soxed' it to the same 44100 Hz as the romans2.wav file, which
plays, but it still appears to be empty. It's like that "4 min. 33
secs" piano piece, total silence.
--
Davey.

ALSA for audio
 

In article , Davey
wrote:
On Sat, 16 Feb 2013 12:43:44 +0000 (GMT) Jim Lesurf
wrote:


A problem with this is that I have no real idea what "EZCap" is. You'd
have to say more about that.

It does the same job as a Hauppaugge TV tuner, with a USB connection.
Similar to a Dazzle. If you really need to know more, I can try, but
we'll stick with that for now.

I wondered if it was something like that as I had a vague memory of hearing
it mentioned on the digital-tv group.

However the Happauge 290e provides a transport data stream on my Linux
boxes. Packets of transport stream data. *Not* demodulated audio or video.
It is left to the computer to convert this. e.g. I can make '.ts'
recordings of data packets and VLC can play them, and ffmpeg can extract
their audio to other formats like lpcm wave. But the actual output I get
from the 290e doesn't contain any actual LPCM audio as such. cf below.



aplay -L with the EZCap added the line:

iec958:CARD=U0xeb1a0x2861,DEV=0 USB Device 0xeb1a:0x2861, USB Audio
IEC958 (S/PDIF) Digital Audio Output

How does aplay -l list it? I'd have guessed from its name that it is a
'capture' device so wouldn't appear at all for aplay -l.


Correct.

Yet you say aplay -L *does* list it above. Odd.

This sounds to me as though the device is being seen and recognised.
Volume Control Sound Preferences also shows it as: 2861 / 1 Input /
Analog Stereo Input, which is good.

What "Volume Control Sound Preferences" do you mean here? How are you
getting that info?


At least on my Ubuntu 10.04 installation, the volume icon in the upper
right has a 'Preferences' option on left-click along with the volume
slider. This leads to a set of dialog boxes, where I can gain access to
the various sound cards, to a limited extent only. The EZCap shows up
here, along with the Internal Card, and the HDMI card.

I can't recall if that is provided bt Pulse rather than alsa. if so, it may
be confusing the issue somewhat.



Try something like arecord -D plughw:2,0,0 -f dat -t wav -d 5 fred.wav

If it can find the device it should give you a five second long wave
file called fred.wav, stereo 48k rate. If not, say what errors it
returns.

It seems to record a file, but I cannot find any data when I play it! I
have 'soxed' it to the same 44100 Hz as the romans2.wav file, which
plays, but it still appears to be empty. It's like that "4 min. 33 secs"
piano piece, total silence.

That sounds like there is no actual stream of data and you aren't making an
ALSA connection. What duration does the file report? (Or how big is it?)

I'm wondering if the 'soundcard' output of the EZCap is akin to that of the
FUnCube I've been using. It provides an 'audio' output you can get using
ALSA. But it is *not* audio data. It is IQ mixdown samples of the RF being
tuned. Requires demodulation to obtain any audio, etc.

Many 'radio/TV' USB dongles actually sample at a few MHz (8 bit samples)
and provide this raw stream. Up to the software in the computer to make
sense of the result. So I don't know what your EZCap does. If that is the
case, then ALSA may have no way to 'convert' it.

What do the specs of the EZCap say about how it outputs data?

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

ALSA for audio
 

In article , Bob Latham
wrote:
In article , Jim Lesurf
wrote:

However there will be an article in Hi Fi News. Just have to get
around to writing it. :-)

Jim,

I'm not for one moment trying to put you off writing for Hi-Fi News I am
a subscriber and have enjoyed reading many of your articles in the
magazine. I do often wonder though, how it sits with you to write for a
magazine that has an editor that comments in the Jan13 issue.

Three decade period of cable testing and crusty engineers who insist
that 'cable sound' is impossible or that the audiophile community is
generally bonkers.

He then goes on to talk about "overwhelming evidence of blind listening
tests on hundreds of interconnects (speakers and line level)"

I have to say I am quite happy to endorse his comments without
reservation in fact I think in some ways it is rather understated.

I am puzzled how you can live with it though.


Quite easy really.

1) My experience is that there are cases where I think a difference is
audible to me, and others where there isn't. (Which actually means I agree
that saying differences are "impossible" can't be correct.)

2) That I doubt a lot of what others claim, but realise there will be times
when they are correct and I'm wrong. Just as there will be other cases
t'other way around. (So others may be right when they say they can hear
some difference which escapes me.)

3) That 'differences' may depend on the circumstances of the situation. So
be evident in some cases, but not others.

4) That there may be 'differences' for other reasons, and they are
mis-ascribed in a way I can't tell for lack of knowledge, etc. One of the
real problems with experiments and tests is mis-understanding the cause of
what is observed.

5) They may also be because the 'control' was flawed. (And such flaws may
also give a null result, also.) Also because the test wasn't that 'blind'
or wasn't repeated often enough for any real significance. It is often
almost impossible in practice to do really reliable tests for things beyond
the so-obvious-and-you-can-easily-find-them-by-measurement differences.
People's hearing alters as they hear things. So if you play the same thing
twice it will tend to sound 'different' the second time.

6) There is no 'Editorial Line' I'm required to follow. I'm not required to
agree with whatever everyone else write in any magazine I get things
published in. :-) People are either happy to publish/read what I've
written, or not.

7) I've never claimed to have particulary good ears. Others almost
certainly have better hearing than mine.

8) I can't quite see any point in adopting an attitude of "I don't
absolutely agree with every word and idea you have, and don't feel certain
you are infallable, so I refuse to write for your magazine." :-)

The bottom line is that the same approach of applying an academic science /
doubting attitude means I have to be as doubting of my own views as that of
others, and similarly for presented 'evidence'.

So I may think he/you *might* be wrong in some cases, may even think it
likely, but have no way to know if I wasn't there and knew all and
controlled all. I can only be skeptical and make my own judgements on the
basis of my own experience and understanding.

FWIW I don't take very seriously many of the opinions in any reviews
either. Simply because I don't actually care what someone else thought of
the 'sound' using music I don't play, via a system I don't have, in a room
different to mine.

What I *can* sometimes do is shoot down the 'scientific explanations'
sometimes trotted out for 'why 'particular ultra-costly items are 'better'.
Usually because flaws in their arguments or evidence conflict with
established physics, etc, or muddle the reality. However that doesn't
necessarily mean their items are crap. Just that their 'explanations' are
twaddle.

People do know my views. Up to them to decide on their own. I simply write
about what interests me, and I hope at least a fair number of readers will
find that informative or of enough interest to read. If that differs from
what others write, etc, fair enough. No point in us all writing exactly the
same thing! :-)

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

ALSA for audio
 

In article , Bob Latham
wrote:
In article , Jim Lesurf
wrote:
In article , Bob Latham
wrote:


5) They may also be because the 'control' was flawed. (And such flaws
may also give a null result, also.) Also because the test wasn't that
'blind' or wasn't repeated often enough for any real significance.

Looking back 20 years ago, the above does possibly have a point but I
think (certainly mine) dealers these days do attempt to give blind tests
(as is practical) especially if they know the customer might smell a rat
otherwise.

The problem is that being 'blind' simply isn't enough to ensure the results
are reliable or mean what people deduce/assume.

Serious tests would have to be double-blind and include 'same' pairs, for
example, as well as 'different'. Then be done enough times with the same
material to show statistical significance. How many dealers (or magazine
reviewers) do all that and provide the details?


It is often almost impossible in practice to do really reliable tests
for things beyond the
so-obvious-and-you-can-easily-find-them-by-measurement differences.

Hmm, OK-ish.

Examples of the problems above. 'Blind' in itself simply isn't sufficient
to establish conclusions are reliable.


People's hearing alters as they hear things. So if you play the same
thing twice it will tend to sound 'different' the second time.

Again, I think we've moved passed this. Certainly, if I can't tell the
demonstrator or controller which of the two items I'm listening to
without other than audible clues then the difference isn't worth paying
for.

Problem is that neither of us can tell for ourself when a review or someone
else *says* it gave an audible difference when we weren't there and don't
know *exactly* what they did.


6) There is no 'Editorial Line' I'm required to follow. I'm not
required to agree with whatever everyone else write in any magazine I
get things published in. :-) People are either happy to publish/read
what I've written, or not.

Don't you think there is a public expectation that you accept the
magazine's *general* views and that you don't think they're part of a
generally bonkers audiophile community simply because you write for them?

Dunno. I can only be responsibile for what I write/think/do. I accept
others views may or not be correct. Having doubts is not the same as being
certain someone else's view is tosh.


FWIW I don't take very seriously many of the opinions in any reviews
either. Simply because I don't actually care what someone else thought
of the 'sound' using music I don't play, via a system I don't have, in
a room different to mine.

That is very fair IMHO.

I'm sure I've said before that I would never attempt to evaluate
anything using classical music. Not because I don't like it (I do) or
because I don't have a reasonable selection (I do) but because classical
music doesn't draw from Hi-Fi the stuff that gives me enjoyment of the
Hi-Fi. I may love the music but not the Hi-Fi playing it. I've not
worded that too well, hope you can see what I was trying to say.

Yes. Similarly I'd be cautious if using pop/rock because I have no idea
what it 'should' sound like. May hear 'differences' but then up to the
listener to decide which they might prefer.

TBH I'd also be cautious with a lot of classical music as material. I tend
to judge using things like Proms or other R3 items from venues I used to
know moderately well. But then I know that audio 'memory' can fade...


I cannot hear the controversial Hi-Fi differences using classical music,
I simply cannot. So is it possible that the differences are only
possible to here on Rock/pop/jazz due to their spectral/dynamic nature
and maybe the type of recording? Could this be a bridge over the
contention?

Pass. :-)

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

ALSA for audio
 

On Sat, 16 Feb 2013 15:58:32 +0000 (GMT)
Jim Lesurf wrote:

In article , Davey
wrote:
On Sat, 16 Feb 2013 12:43:44 +0000 (GMT) Jim Lesurf
wrote:


A problem with this is that I have no real idea what "EZCap" is.
You'd have to say more about that.

It does the same job as a Hauppaugge TV tuner, with a USB
connection. Similar to a Dazzle. If you really need to know more, I
can try, but we'll stick with that for now.

I wondered if it was something like that as I had a vague memory of
hearing it mentioned on the digital-tv group.


Yes, there was a quite long thread about it.

However the Happauge 290e provides a transport data stream on my Linux
boxes. Packets of transport stream data. *Not* demodulated audio or
video. It is left to the computer to convert this. e.g. I can make
'.ts' recordings of data packets and VLC can play them, and ffmpeg
can extract their audio to other formats like lpcm wave. But the
actual output I get from the 290e doesn't contain any actual LPCM
audio as such. cf below.


That might be worth a try.


aplay -L with the EZCap added the line:

iec958:CARD=U0xeb1a0x2861,DEV=0 USB Device 0xeb1a:0x2861, USB
Audio IEC958 (S/PDIF) Digital Audio Output

How does aplay -l list it? I'd have guessed from its name that it
is a 'capture' device so wouldn't appear at all for aplay -l.


Correct.

Yet you say aplay -L *does* list it above. Odd.


Yes, I just checked my log again, and I believe I was very careful
making the log, for this reason.

This sounds to me as though the device is being seen and
recognised. Volume Control Sound Preferences also shows it as:
2861 / 1 Input / Analog Stereo Input, which is good.

What "Volume Control Sound Preferences" do you mean here? How are
you getting that info?


At least on my Ubuntu 10.04 installation, the volume icon in the
upper right has a 'Preferences' option on left-click along with the
volume slider. This leads to a set of dialog boxes, where I can
gain access to the various sound cards, to a limited extent only.
The EZCap shows up here, along with the Internal Card, and the HDMI
card.

I can't recall if that is provided bt Pulse rather than alsa. if so,
it may be confusing the issue somewhat.


'About' just says that it is part of the Indicator Applet, but no idea
how it gets its information.


Try something like arecord -D plughw:2,0,0 -f dat -t wav -d 5
fred.wav

If it can find the device it should give you a five second long
wave file called fred.wav, stereo 48k rate. If not, say what
errors it returns.

It seems to record a file, but I cannot find any data when I play
it! I have 'soxed' it to the same 44100 Hz as the romans2.wav file,
which plays, but it still appears to be empty. It's like that "4
min. 33 secs" piano piece, total silence.

That sounds like there is no actual stream of data and you aren't
making an ALSA connection. What duration does the file report? (Or
how big is it?)


It is played as a 5 sec. silent file, and is 937.5 KB in size. The
'arecord' part worked, there is just no data.

I'm wondering if the 'soundcard' output of the EZCap is akin to that
of the FUnCube I've been using. It provides an 'audio' output you can
get using ALSA. But it is *not* audio data. It is IQ mixdown samples
of the RF being tuned. Requires demodulation to obtain any audio,
etc.

It is, I believe, similar to a Hauppaugge, as it does the same job.

Many 'radio/TV' USB dongles actually sample at a few MHz (8 bit
samples) and provide this raw stream. Up to the software in the
computer to make sense of the result. So I don't know what your EZCap
does. If that is the case, then ALSA may have no way to 'convert' it.

Ok. Does this suggest Folderol's Jack after all, or some other software?

What do the specs of the EZCap say about how it outputs data?

Very, very little. It is clearly a) mostly concerned with video, and b)
is very much a Windows/Mac oriented system.

Maybe I'll try it with the Win 7 software, as I know it works with that
for TV.

I'll also try the Hauppaugge instead of the EZCap.

Thanks.
--
Davey.

ALSA for audio
 

On Sat, 16 Feb 2013 20:00:06 +0000
Davey wrote:

On Sat, 16 Feb 2013 15:58:32 +0000 (GMT)
Jim Lesurf wrote:

In article , Davey
wrote:
On Sat, 16 Feb 2013 12:43:44 +0000 (GMT) Jim Lesurf
wrote:



Big snip


It is clearly a) mostly concerned with video, and
b) is very much a Windows/Mac oriented system.

Maybe I'll try it with the Win 7 software, as I know it works with
that for TV.

I'll also try the Hauppaugge instead of the EZCap.

Thanks.

Did some more experimenting, now more confused than ever.
The Hauppauge acted even less noticeably than the EZCap, there was no
change to any of the a-play or-record, -l or -L readouts.
Played around to try to get vlc to Capture the EZCap, but failed, but
that might just be my lack of knowledge.
Went into Win 7, the natural 'home' of both devices. With the
Hauppauge, I was able to record a Composite stream, of blank video and
stereo audio.
With the EZCap, I had to introduce a different video signal, as it
would not record unless there was a valid video source. Not a problem.
The EZCap produced a *.mpg file the Hauppauge, a *.ts file.
Then to really confuse me, vlc, which is set tp play using ALSA and the
inbuilt soundcard, will not play the audio from either, but Totem will
play the .mpg file.
I'm still trying to find something that will play the .ts file;
tomorrow.
--
Davey.

ALSA for audio
 

I've added the digital-tv group to this as someone there may be able to
clear up points I'm not sure about!...

n article , Davey
wrote:
On Sat, 16 Feb 2013 20:00:06 +0000 Davey wrote:


Did some more experimenting, now more confused than ever. The Hauppauge
acted even less noticeably than the EZCap, there was no change to any of
the a-play or-record, -l or -L readouts. Played around to try to get vlc
to Capture the EZCap, but failed, but that might just be my lack of
knowledge.

So far as I know, the 290e demodulates the DTTV stream to the point of
supplying a 'transport stream' of data packets. I don't know the 'EZCap'
but it may be similar. If so, this then relies on software running on the
'host' computer to extract the packeted data and generate audio (or video).

If so, using arecord won't get anything meaningful. You need to use things
like tzap or VLC to make sense of the output.

How did you tune the EZCap and tell it which 'station' you wanted?

Went into Win 7, the natural 'home' of both devices. With the
Hauppauge, I was able to record a Composite stream, of blank video and
stereo audio.

You'd need to say more about what software you used. Someone who uses
Windows may then be able to comment.

With the EZCap, I had to introduce a different video
signal, as it would not record unless there was a valid video source.
Not a problem. The EZCap produced a *.mpg file the Hauppauge, a *.ts
file.

That's the sort of thing I'd expect. Here the Happauge can give me a .ts
output and I can choose what packets to include. (In fact, all of them if I
want to record and entire mux for later processing.) It doesn't of itself
provide LPCM audio. That is left to software on the computer, not in the
290e.

Then to really confuse me, vlc, which is set tp play using ALSA
and the inbuilt soundcard, will not play the audio from either, but
Totem will play the .mpg file. I'm still trying to find something that
will play the .ts file; tomorrow.

ALSA has nothing to do with playing .ts or .mpg files / streams. Down to
the playing program to make sense of them. Beyond that you'd need to use
something like the ffmpeg family to examine the files and interpret or
manipulate their contents/formats.

My impression so far as that you can't get the EZCap working as an ALSA
source because it simply doesn't - of itself - provide a conventional audio
stream. Getting that from its output is left to other software on your
computer. But I don't know the device, so can't be sure about that.

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

ALSA for audio
 

Its a whole new world.


grin.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Jim Lesurf" wrote in message
...
I've added the digital-tv group to this as someone there may be able to
clear up points I'm not sure about!...

n article , Davey
wrote:
On Sat, 16 Feb 2013 20:00:06 +0000 Davey wrote:


Did some more experimenting, now more confused than ever. The Hauppauge
acted even less noticeably than the EZCap, there was no change to any of
the a-play or-record, -l or -L readouts. Played around to try to get vlc
to Capture the EZCap, but failed, but that might just be my lack of
knowledge.

So far as I know, the 290e demodulates the DTTV stream to the point of
supplying a 'transport stream' of data packets. I don't know the 'EZCap'
but it may be similar. If so, this then relies on software running on the
'host' computer to extract the packeted data and generate audio (or
video).

If so, using arecord won't get anything meaningful. You need to use things
like tzap or VLC to make sense of the output.

How did you tune the EZCap and tell it which 'station' you wanted?

Went into Win 7, the natural 'home' of both devices. With the
Hauppauge, I was able to record a Composite stream, of blank video and
stereo audio.

You'd need to say more about what software you used. Someone who uses
Windows may then be able to comment.

With the EZCap, I had to introduce a different video
signal, as it would not record unless there was a valid video source.
Not a problem. The EZCap produced a *.mpg file the Hauppauge, a *.ts
file.

That's the sort of thing I'd expect. Here the Happauge can give me a .ts
output and I can choose what packets to include. (In fact, all of them if
I
want to record and entire mux for later processing.) It doesn't of itself
provide LPCM audio. That is left to software on the computer, not in the
290e.

Then to really confuse me, vlc, which is set tp play using ALSA
and the inbuilt soundcard, will not play the audio from either, but
Totem will play the .mpg file. I'm still trying to find something that
will play the .ts file; tomorrow.

ALSA has nothing to do with playing .ts or .mpg files / streams. Down to
the playing program to make sense of them. Beyond that you'd need to use
something like the ffmpeg family to examine the files and interpret or
manipulate their contents/formats.

My impression so far as that you can't get the EZCap working as an ALSA
source because it simply doesn't - of itself - provide a conventional
audio
stream. Getting that from its output is left to other software on your
computer. But I don't know the device, so can't be sure about that.

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

ALSA for audio
 

Jim Lesurf wrote:
I've added the digital-tv group to this as someone there may be able to
clear up points I'm not sure about!...

n article , Davey
wrote:
On Sat, 16 Feb 2013 20:00:06 +0000 Davey wrote:


Did some more experimenting, now more confused than ever. The Hauppauge
acted even less noticeably than the EZCap, there was no change to any of
the a-play or-record, -l or -L readouts. Played around to try to get vlc
to Capture the EZCap, but failed, but that might just be my lack of
knowledge.

So far as I know, the 290e demodulates the DTTV stream to the point of
supplying a 'transport stream' of data packets. I don't know the 'EZCap'
but it may be similar. If so, this then relies on software running on the
'host' computer to extract the packeted data and generate audio (or video).

If so, using arecord won't get anything meaningful. You need to use things
like tzap or VLC to make sense of the output.

How did you tune the EZCap and tell it which 'station' you wanted?

I think the ezcap is just analogue input - there's probably a way to
select between s-video and composite unless it only takes one at a time.

There is no tuning - it doesn't have a tuner.

I guess it just outputs yuv + pcm and lossless compresses it, sends it
over over usb and the specific v4l driver decompresses it and presents
yuv and pcm.

Of course the device may not be properly supported.

The output of the new lines in dmesg after plugging would be useful.

To get audio to appear on the alsa device I think you will need to set
up with v4l or a use a player.

ALSA for audio
 

On Sun, 17 Feb 2013 09:41:34 +0000 (GMT)
Jim Lesurf wrote:

I've added the digital-tv group to this as someone there may be able
to clear up points I'm not sure about!...

n article , Davey
wrote:
On Sat, 16 Feb 2013 20:00:06 +0000 Davey
wrote:


Did some more experimenting, now more confused than ever. The
Hauppauge acted even less noticeably than the EZCap, there was no
change to any of the a-play or-record, -l or -L readouts. Played
around to try to get vlc to Capture the EZCap, but failed, but that
might just be my lack of knowledge.

So far as I know, the 290e demodulates the DTTV stream to the point of
supplying a 'transport stream' of data packets. I don't know the
'EZCap' but it may be similar. If so, this then relies on software
running on the 'host' computer to extract the packeted data and
generate audio (or video).

If so, using arecord won't get anything meaningful. You need to use
things like tzap or VLC to make sense of the output.

How did you tune the EZCap and tell it which 'station' you wanted?

Went into Win 7, the natural 'home' of both devices. With the
Hauppauge, I was able to record a Composite stream, of blank video
and stereo audio.

You'd need to say more about what software you used. Someone who uses
Windows may then be able to comment.

With the EZCap, I had to introduce a different video
signal, as it would not record unless there was a valid video
source. Not a problem. The EZCap produced a *.mpg file the
Hauppauge, a *.ts file.

That's the sort of thing I'd expect. Here the Happauge can give me
a .ts output and I can choose what packets to include. (In fact, all
of them if I want to record and entire mux for later processing.) It
doesn't of itself provide LPCM audio. That is left to software on the
computer, not in the 290e.

Then to really confuse me, vlc, which is set tp play using ALSA
and the inbuilt soundcard, will not play the audio from either, but
Totem will play the .mpg file. I'm still trying to find something
that will play the .ts file; tomorrow.

ALSA has nothing to do with playing .ts or .mpg files / streams. Down
to the playing program to make sense of them. Beyond that you'd need
to use something like the ffmpeg family to examine the files and
interpret or manipulate their contents/formats.

My impression so far as that you can't get the EZCap working as an
ALSA source because it simply doesn't - of itself - provide a
conventional audio stream. Getting that from its output is left to
other software on your computer. But I don't know the device, so
can't be sure about that.

Slainte,

Jim


Briefly, as am on point of going out to a birthday party:

All of that makes sense, from what I know. I don't know how to
manipulate the various ffmpeg and .ts streams, so I'll look at that
later. I briefly tried to point vlc at the EXCap, but I couldn't find
the correct Audio Input string. Maybe later, again.
The EZCap, in its Windowos program, ARCSoft, has adjustments for the
video source (I use it to accept NTSC 443), and it just takes in the
video, seemingly independent of the video source.
More later.

Thanks again.
--
Davey.