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

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

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.

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.

In article , Andy Furniss
wrote:
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!...



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.

To summarise what has 'gone before' on the Linux and audio groups...

Davey has been trying to get audio output from the EZCap via ALSA. The
'arecord -l' command does seem to list what he says is the EZCap. But
attempts to read in the audio and capture it give either errors or an
all-zero-sample-values recording.

I've been over the basic ways to determine the device ID under ALSA and how
to connect. But it seems not to co-operate. So I've been wondering about
the cause of the problem. In particular if it isn't really providing a
fully demodulated audio output.

Thought this because the FUNcube I'm using does output over ALSA, but the
output is IQ samples *not* audio, so need post-processing. In an earlier
posting Davey said his Windows software for the EZCap gave mpg output...

Hence I'm currently trying to decide if his working on having EZCap output
audio (without some further processing on the computer) is chasing a
boojum. So not an 'alsa' problem at all. But I dunno as I know zero about
the EZCap. My experience is only with the 290e and FUNcube.

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

Jim Lesurf wrote:
Hence I'm currently trying to decide if his working on having EZCap output
audio (without some further processing on the computer) is chasing a
boojum. So not an 'alsa' problem at all. But I dunno as I know zero about
the EZCap. My experience is only with the 290e and FUNcube.

I have the Easycap dongle and a couple of USB tuner sticks and they are
very different devices. The Easycap (or EZCap) is basically a digitizer
which samples an analogue composite video or S-video input, with audio,
and sends PCM data to the USB. I don't know to what extent that data is
compressed, but I do know that it requires a fast USB connection and a
fast processor otherwise it simply won't work.

EZcap can be used with VLC if a driver is installed, but this is as a
video capture device and not as a tuner device such as the Hauppauge,
which supplies an MPEG2 or H.264 transport stream.

Jim Lesurf wrote:
In article , Andy Furniss
wrote:
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!...



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.

To summarise what has 'gone before' on the Linux and audio groups...

Davey has been trying to get audio output from the EZCap via ALSA. The
'arecord -l' command does seem to list what he says is the EZCap. But
attempts to read in the audio and capture it give either errors or an
all-zero-sample-values recording.

I wouldn't expect that to work without having the v4l drivers setup and
running the device.


I've been over the basic ways to determine the device ID under ALSA and how
to connect. But it seems not to co-operate. So I've been wondering about
the cause of the problem. In particular if it isn't really providing a
fully demodulated audio output.

Unlikely - but even if it were you would hear/record something.


Thought this because the FUNcube I'm using does output over ALSA, but the
output is IQ samples *not* audio, so need post-processing. In an earlier
posting Davey said his Windows software for the EZCap gave mpg output...

The windows software will probably (badly) convert to mpeg on the fly
because it's not practical to save as raw video. Of course it's possible
the device has a hardware encoder - but more likely not.

Some probing with v4l-ctl should give more info.

Hence I'm currently trying to decide if his working on having EZCap output
audio (without some further processing on the computer) is chasing a
boojum. So not an 'alsa' problem at all. But I dunno as I know zero about
the EZCap. My experience is only with the 290e and FUNcube.

Looking at Johns' post it seems that ezcap will work with VLC - I think
getting this to work should be the first thing, and also not testing
initially with a rare format like NTSC 443.

Andy Furniss wrote:

Looking at Johns' post it seems that ezcap will work with VLC

Forgot about the crosspost - maybe that's with windows.

In article , John
Legon
wrote:
Jim Lesurf wrote:
Hence I'm currently trying to decide if his working on having EZCap
output audio (without some further processing on the computer) is
chasing a boojum. So not an 'alsa' problem at all. But I dunno as I
know zero about the EZCap. My experience is only with the 290e and
FUNcube.

I have the Easycap dongle and a couple of USB tuner sticks and they are
very different devices. The Easycap (or EZCap) is basically a digitizer
which samples an analogue composite video or S-video input, with audio,
and sends PCM data to the USB. I don't know to what extent that data is
compressed, but I do know that it requires a fast USB connection and a
fast processor otherwise it simply won't work.

That may mean the problem is that Davey either can't identify the format
for the audio, or that it has to be processed on the host machine.

ALSA can routinely do things like shuffle between 16bit and 24bit and LE
and BE byte sets. Even resample/convert the sample rate. But not do things
like decode mp3, say. That needs the addition of some other software
process in the chain.

I don't have an EZCap. So can't do any tests. Davey reports the EZCap as
giving alsa device ID numbers and strings. But then says he gets 'empty'
streams (0 values) when using these with arecord. Which indicates something
somewhere isn't set up correctly by him. But I can't tell what the problem
may be from here. :-)

I've had such empty results from another device. But that was IIUC because
the device was being controlled incorrectly. That may also be true here.
The problem there seemed to be a bug in some versions of the HID USB
libraries. I changed library and the code worked. But if that's the problem
his software may need re-compiling and linking against an alternative
library.

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

Jim Lesurf wrote:

I don't have an EZCap. So can't do any tests. Davey reports the EZCap as
giving alsa device ID numbers and strings. But then says he gets 'empty'
streams (0 values) when using these with arecord. Which indicates something
somewhere isn't set up correctly by him. But I can't tell what the problem
may be from here. :-)

If things are not correctly set then it's certainly possible for the
device to initialize OK but to give a completely blank recording...