Hiss on capture from VHS
Ken Blanchard
Graham
news:3e6d110d$1...@text-west.newsgroups.com...
>I captured a VHS tape to the hard drive and burned it to a DVD-RW. I
noticed a high frequency hiss >present on the DVD and checked the MPEG and
it is there on the capture also. It is not present when I >play the VHS
tape. Any thoughts on how to filter the hiss out during the capture, or
process the Mpeg2 file >to remove the hiss?
Split using Tmpgenc into separate video/audio. Use CoolEdit 2000 to
"de-noise" the audio, then use TmpGenc to re-combine into one file.
PS Dont post in HTML !
Larry S. Horwitz
the sound cards have automatic gain control (AGC) which brings up background
noise and hiss. These can often be switched "off". There are also equalizers
which apply selective audio filtering, which allow hiss reduction if the
noise is not broadband.
Larry
"Graham" <spamh4t3...@hotmail.com> wrote in message
news:b4kgqh$203c35$1...@ID-158414.news.dfncis.de...
Ken Blanchard
> "de-noise" the audio, then use TmpGenc to re-combine into one file.
Will Tmpgenc split the Mpeg2 or does it need to be an Avi?
> PS Dont post in HTML !
Sorry. Thought it was set to plain text.
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Ken Blanchard
"Larry S. Horwitz" <LSHo...@adelphia.net> wrote in message
news:_Olba.77$cG1.1...@news1.news.adelphia.net...
> How do you capture audio? Is it analog or through a DV interface? Some of
> the sound cards have automatic gain control (AGC) which brings up
background
> noise and hiss. These can often be switched "off". There are also
equalizers
> which apply selective audio filtering, which allow hiss reduction if the
> noise is not broadband.
>
> Larry
I have an Asus A7V333 with onboard audio.
Ken
Ken Blanchard
Onboard audio-ASUS A7V333
Larry S. Horwitz
Since each sound card has its' own driver software, it is difficult to
generalize, but the All In Wonder card does loop the audio from your VHS
source into the sound input (Line In) of your onboard ASUS audio on the
motherboard. If your driver software offers an AGC on/off switch, you should
turn it off.
The hiss is most likely arising because you have too much recording gain set
on your PC, too little audio signal from the VHS deck, or both. I say this
since the VHS tape apparently does not have this background noise
inherently, but it shows up only when you capture. I assume you have no
output level adjustment on the VCR and thus cannot control the audio output
signal strength, and are taking the audio directly from the stereo "Line
Out" jacks of the VHS deck into the ATI breakout box.
As an experiment you can try recording a few samples of video with different
audio recording levels for the audio to see if any settings result in a
clean and noise free background. Alternately, try recording a sample with
the audio recording level turned down all the way, to see if the hiss is
proportionate to the recording gain control (in which case the noise is in
the input signal) or stays constant, in which case it is inherent in your
on-board sound. Most on the on-board sound boards have pretty poor signal to
noise ratios compared to dedicated sound cards.
The post capture approach of demuxing and noise filtering only works well if
the noise is narrow banded. If you have broadband noise, all you will do is
muddy up the sound and not really improve the signal-to-noise ratio. Again,
a short trial clip will assist you in seeing what results you can achieve.
Larry
"Ken Blanchard" <kblan...@ipapilot.org> wrote in message
news:3e6dfa34$1...@text-west.newsgroups.com...
Graham
> > Split using Tmpgenc into separate video/audio. Use CoolEdit 2000 to
> > "de-noise" the audio, then use TmpGenc to re-combine into one file.
>
> Will Tmpgenc split the Mpeg2 or does it need to be an Avi?
Yes, it will do this with mpeg2, select File/Mpeg Tools/Simple Demultiplex
and select destination
Linea Recta
|\ /|
| \/ |@rk
\../
\/os
"Ken Blanchard" <kblan...@ipapilot.org> schreef in bericht
news:3e6dfa34$1...@text-west.newsgroups.com...
Larry S. Horwitz
"Linea Recta" <mccm.vos-...@hccnet.nl> wrote in message
news:b4lgaj$20nhjq$1...@ID-54604.news.dfncis.de...
Linea Recta
it's a commercial tape)
|\ /|
| \/ |@rk
\../
\/os
"Larry S. Horwitz" <LSHo...@adelphia.net> schreef in bericht
news:Ryrba.833$cG1.2...@news1.news.adelphia.net...
Larry S. Horwitz
synch and chrominance) signals and not the audio signal. A poorly adjusted
television or VCR could conceivably generate audible hiss as a by-product of
Macrovision, but this is extremely unlikely, and would not be at all likely
to cause the capture problem which was posted.
"Linea Recta" <mccm.vos-...@hccnet.nl> wrote in message
news:b4o2og$229buk$1...@ID-54604.news.dfncis.de...
Mumbles
<LSHo...@adelphia.net> wrote:
>As an experiment you can try recording a few samples of video with different
>audio recording levels for the audio to see if any settings result in a
>clean and noise free background. Alternately, try recording a sample with
>the audio recording level turned down all the way, to see if the hiss is
>proportionate to the recording gain control (in which case the noise is in
>the input signal) or stays constant, in which case it is inherent in your
>on-board sound. Most on the on-board sound boards have pretty poor signal to
>noise ratios compared to dedicated sound cards.
>
>The post capture approach of demuxing and noise filtering only works well if
>the noise is narrow banded. If you have broadband noise, all you will do is
>muddy up the sound and not really improve the signal-to-noise ratio. Again,
>a short trial clip will assist you in seeing what results you can achieve.
>
>Larry
>
Also, from apart of the gain controls as Larry explains above. Go to
control panel/sounds, get the windows mixer up. Then make sure that
things like mike input, cd etc are all set to mute while you record.
mumbles
Ken Blanchard
troubleshooting suggestions helped lead me to the suspect problem. I have
tried all combinations of muting, selections, etc. and have reached the
conclusion that the problem is inherent in the CMedia 8738 chip on the ASUS
A7V333 motherboard. It evidently has a noise issue only on input, but clean
output. I've attached a message that I found from another forum that
explains another's experience with this problem.
I took a SB Live 5.1 card from another machine and I get clear sound from
the capture. I would prefer a solution to the onboard sound capture problem
if anyone has suggestions based on this furthur info. I did have the latest
CMedia driver installed, but downloaded and reinstalled it for
troubleshooting...no change.
Thanks.
Ken
----------------------------------------------------------------------------
------------------
Noisy (8-bit?) Audio during Recording (workaround found, and it wasn't
ATI's fault!)
When I first got the system set up, there was a fairly high level of
background hiss being recorded into any digital VCR file...
...This hiss was not present while viewing live TV. And
it was definitely embedded in the recorded file, and not part of the
playback process, as I could replicate the problem by playing the file back
on another machine. Likewise, playing back MPGs and AVIs that were created
on another computer, there would be no hiss. The hiss problem was also
evident during any TV-on-Demand (TVoD) viewing operations. (TVoD is ATI's
instant replay mode of video playback. It records the TV signal to the hard
drive for immediate playback, or pausing live TV, or instant replay, etc.,
much like TiVo and Replay-TV.) This hiss still existed, even in spite of the
fact that all video recording quality settings that I have ever used only
had 16-bit audio modes...
...No muting or level changes of any of the audio inputs or outputs made any
difference in resolving this issue. Furthermore, other sound sources, such
as audio CD playback, DVD-video playback, system sounds, synthesized music,
etc. -- all of them -- played back flawlessly. I could even make perfect
16-bit stereo recordings of CDs; they played back cleanly and without any
audible hiss.
... a number of Asus and Soyo motherboard
owners complained about the C-Media audio chips that are on their
motherboards. I recall one Asus owner mentioning that his CMedia chip
couldn't pick up voice commands from his microphone while he was playing a
certain game that had simultaneous audio output. Another clue was revealed
in Microsoft's Knowledge Base . (Do a search on "Full Duplex" while
specifying product "Netmeeting," and read the resulting articles.) Lastly, I
found a brief blurb on the CMedia web site regarding difficulties with one
of CMedia's lesser chips and certain IP telephony products or video
teleconferencing:
CMI8330 Sound Chip
Question: 8. How come full-duplex functions don't work?
Answer: Because CMI8330 uses two devices (SB16 & WSS) to perform full-duplex
functions, some applications may detect that CMI8330 is not full-duplex. To
avail yourself of full-duplex functions, please select different wave
devices between the playback and the recording in audio setup of that
program. Or you can set the playback and the recording devices to different
ones in "Multimedia" of "Control Panel". In Iphone 5.0, please set the
full-duplex function forcibly, then the full-duplex functions will be
working fine.
Note that most IP telephony products, including Netmeeting, require full
duplex audio capability to operate in the highest quality audio mode. Full
duplex audio is a mode when both recording and playback is being done at the
same time. It is also used by TVoD because the live audio output from the
ATI TV-tuner is being recorded by the sound card at the same time that the
recorded audio signal is immediately played back from the hard drive. The
problem with the earlier CMedia chip, as described on their own web site, is
that recording is done by the WSS portion of the chip, while playback is
done by the SB16 compatible portion of the chip. CMedia claims that some
programs are misidentifying this CMedia chip as being only half-duplex
capable, and they describe a method to force such programs to operate in
full duplex mode by using two different modes of the chip concurrently.
Microsoft describes a similar workaround for some hardware configurations
used with Netmeeting. Unfortunately, I don't believe that the ATI software
can use two different sound cards simultaneously -- one for recording, one
for playback. This capability is controlled in Windows by setting the
"Preferred Device" fields in the Audio panel of the Control Panel - it's in
the Sounds and Multimedia section - and my Cmedia drivers only offer one
choice for recording or playback devices in Windows 2000 - there is no
separate SB16 or WSS entry for each field.
I can only surmise that the aforementioned Asus user's game and ATI's
Multimedia Center are both being tripped up by the "split personality" of
the early CMedia chip during recording and playback, and that this same
SB16/WSS design is used for the more powerful CMedia 8738 chip that I have
on my motherboard.
My own opinion, at this point, is that the flaw is in the CMedia drivers, or
even in the limits of the chip's hardware design. I'm going to refer to this
chip as "three-quarter-duplex" capable, in spite of CMedia's claim that it
is a full duplex device. For most users, who don't need full duplex
capability for audio/video teleconferencing via Netmeeting, or who don't
need the simultaneous record/playback capability that TVoD and digital-VCR
both require, this onboard sound chip will provide a fine audio solution.
But any ATI All in Wonder users should look elsewhere for full duplex audio.
I still think that this Soyo motherboard is a great product, but the onboard
sound is not an audiophile or teleconferencing solution. Anyone who expects
to use voice over IP "soft phone" capabilities should also keep this in
mind.
My workaround was to buy a Turtle Beach Santa Cruz sound card for $80.
Yep... I gave up; threw in the towel; wimped out! :) A number of users in
various Rage3d forums have suggested that this near-audiophile-grade card
works flawlessly with the 8500DV, and I certainly concur. It offers me full
duplex capability, stable drivers and a functional mixer, and even has a
S/PDIF output to send a digital audio signal from my DVD player to my home
theater amplifier. Unfortunately, I have to give up the two-way digital
audio capability of the CMedia chip to make this work. The CMedia circuit on
the Soyo motherboard also has two Toslink connectors for a bidirectional
fiber-optic hookup to my home theater amplifier, and I would have preferred
to use these.
Perhaps someday CMedia will surprise me by releasing new drivers which can
support most software in full duplex mode without going through extra
configuration steps, but I wasn't about to wait for their solution.
Likewise, knowing ATI, they may never get around to tweaking Multimedia
Center so that it can recognize the "three quarter duplex" capability of the
CMedia chips, but if they ever do, I'll probably have a nice sound card for
sale on E-bay shortly thereafter. I'll check both companies' web sites
regularly, and I'll keep you posted here.
Ed M.
cards and C-Media audio implementations has been floating around
various groups for a while now.
A few factors conspire to produce this problem.
1) The audio ouput of the offending ATI card contains excessive noise
that is outside of the audio band. Measurements of an all-in-wonder
7500 show noise extending to hundreds of kilohertz with spectral
density that rises to be many dB higher than the level of the in-band
audio noise. (This is a normal consequence of some types of audio
processing and circuitry that does this is said to be doing
"noise-shaping".)
2) The offending C-Media 8738 audio chip does not employ an
oversampling type of analog-to-digital converter.
3) The manufacturer (Soyo, Asus, etc?) that uses the C-Media chip
connects the audio into the chip without any input filtering.
Under these conditions, the C-Media a-d converter creates a
substantial audio hiss because it aliases a huge bandwidth of
huge-amplitude out-of-band noise down in to the audio band.
Any digitized audio will have the hiss. It will show up on recordings.
It will also show up when monitoring the "record" half of the C-Media
chip - I see it easily listening to Roxio Spin Doctor, and can see it
clearly with the TrueRTA audio analyzer (by True Audio).
Audio that passes through the system without being digitized will not
have the excess hiss. This is what happens when the ATI tv tuner is
fed to the audio line-in and listened to 'live' through the line-out
-- it sounds just fine. The C-Media pass-through path is very wide
bandwith, but your ears will not respond to the high-frequency noise
even if your speakers could reproduce it.
On the Soyo SY-K7V Dragon Plus, the hiss is not noticeable when (one
channel of ) the ATI audio is fed to the mic input. Measurements show
that the mic input is filtered, and its frequency response begins
falling off at 6dB/octave a little above 10kHz. That is the right
thing to do. In contrast, the line input shows no indication of
filtering - put in a 45.1kHz sine wave at 44.1kHz sampling rate and
you will get a perfect digital 1kHz tone just as though the sine wave
was 1kHz (45.1-44.1=1kHz). Same goes for a 89.2 kHz sine wave
(89.2-2*44.1=1kHz). And on it goes.
Whose fault?
- ATI should have included filters to knock down the out-of-band noise
that its chips produce.
- Soyo should have provided anti-aliasing filters at the input of the
C-Media chip. The ATI situation is particularly pronounced, but all
sources have some wideband noise, and lack of filtering means that a
recording ends up noisier than it has to be because of the aliasing.
(Either one would do the trick, and one manufacturer could probably
blame the other, but both could be said to be deficient.)
How to fix?
- For sources like vhs tape, don't run the audio through the ATI
dongle. Unplug the ATI audio and run the vhs audio straight into the
line-in. If the vhs is clean, this will make the noise about 20dB
better, and the signal level will actually be higher (audio through
the ATI card loses about 10dB of signal), for a 30dB improvement.
Can't do this for the tuner, though.
- Add your own filtering. A .005uF capacitor across each (L and R) of
the ATI outputs will make a noticeable difference, but it won't
eliminate the problem.
- Run the ATI analog audio through an good external a-d device and use
the C-Media s/pdif input.
- Switch to an audio card that takes care of out-of-band stuff (proper
anti-aliasing, better when combined with an oversampling a-d
converter).
What's not going to help (much):
- Drivers - they're not the problem, unless they could reach out and
do something about analog (continuous-time) hardware filtering.
- Fiddling with audio levels.
- Fiddling with the recording itself. Once the noise is sampled into
the audio, you can't affect it without affecting the signal as well.
You have to catch it while it's out-of-band before it's aliased.
And just to be definite - this is not a full-duplex or 8-bit audio
problem. Examine the contents of a recorded .wav file - it shows the
samples filling all 16 bits.
As a final note, the Soyo implementation of the C-Media analog
line-out has no filtering either, so a digital source (.wav file,
s/pdif input etc.) gets reproduced as a staircase waveform (no
reconstruction filters). This is not much of a problem if all you do
is listen to it, or even if it goes into a digital system that limits
itself to the audio band.
(If you want to see some of this, get the free copy of TrueRTA and
monitor the spectrum of the line input with and without your ATI card
connected.) www.trueaudio.com
The above observations were made on a Soyo SY-K7V Dragon Plus with an
ATI All-in-wonder Radeon 7500. The explanation should apply to
systems with similar hardware that have similar symptoms.
Hope this helps.
Ed.
"Ken Blanchard" <kblan...@ipapilot.org> wrote in message news:<3e708738$1...@text-west.newsgroups.com>...
Ken Blanchard
Ken