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VirtualDub possible with USB 2.0 tv boxes?

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Anonymous
June 1, 2004 6:02:45 PM

Archived from groups: rec.video.desktop (More info?)

Hi all,
Is it possible to use VirtualDub with the USB 2.0 tv capture boxes? Will
the wdm to vfw bridge see them? I would like to have access to the
uncompressed video stream (of course :-) ) from VirtualDub.

And how will I be able to capture the audio? VirtualDub captures audio
using the normal Windows audio capture, and you usually select the input
via the normal Windows Volume Control -> Recording section... so... will
the driver of the USB 2.0 tv box (or the wdm-vfw bridge) create another
device in the Windows Volume Control / Recording devices, or how else
could I make VirtualDub record such audio input?



Otherwise, I would be even happy to use another capture program, as long
as I can use **at least the Huffyuv and the Mainconcept MJPEG encoder**
(which are vfw codecs AFAIK), but in the past (with a bt878 pci card) I
tried lots of programs like iuVcr, Avi_IO and many others, but they
would ALL go out of A/V sync pretty quickly. That's why I want to use
virtualdub now. I suspect that the situation with A/V sync might be
better with an USB 2.0 capture device because the audio and the video
are captured together so probably they don't need software correction
for staying in sync but this is all in theory and I would like to hear
real experiences from you.


If you have any recommendation of specific USB 2.0 tv boxes I would be
interested in hearing those also. I'm interested in these specs:
- being able to deliver raw uncompressed stream
- VirtualDub being able to see such stream
- high sampling (capture) quality, disregarding hardware compression
- capture PAL at 768x576 (not 720x576)


Thanks in advance

More about : virtualdub usb boxes

Anonymous
June 2, 2004 3:16:48 AM

Archived from groups: rec.video.desktop (More info?)

>but in the past (with a bt878 pci card) I
>tried lots of programs like iuVcr, Avi_IO and many others,

Uhmmm, sorry to jump in here. AVI_IO will NOT get out of sync. If you
had the impression that it did, the problem is with playing back the
video.

You can verify this by yourself. Just captuer with AVI_IO, then using
either the propperty sheed of windows explorer or some other software
that provides the information look at how many frames and audio
samples there are in the video. If you divide them by their rate (i.e
25'000 frames / 25 fps, 44100000 / 44100) you both times should get an
identical number which may differs behind the 5 or sixt digit after
the radix. If this condition is met the video is "in sync". This does
not mean that it have to PLAY in sync - but then, as mentioned, the
problem lies somewhere else and is not related to the capture process.

Feel free to get in touch with me for me and you to work out where the
problem is. AVI_IO simply can't capture out of sync.

Markus
Anonymous
June 2, 2004 3:16:49 AM

Archived from groups: rec.video.desktop (More info?)

Markus Zingg wrote:

>>but in the past (with a bt878 pci card) I
>>tried lots of programs like iuVcr, Avi_IO and many others,
>
>
> Uhmmm, sorry to jump in here. AVI_IO will NOT get out of sync. If you
> had the impression that it did, the problem is with playing back the
> video.

Nope, it DID get out of sync when I tried it.
Even if I set the slider at least 5 minutes away from the beginning, it
was out of sync. I did not need to reach that position after a
continuous playing (but even when I did that, it was the same result).

The total number of audio and video samples itself is not a guarantee
that A/V will be in sync.

VirtualDub duplicates or drops video frames in order to maintain sync
(VirtualDubMod is even smarter: performs audio resampling on the fly and
does not drop anything). What kind of algorithm is AVI_IO supposed to
use for the enforcement of A/V sync?


I'm sorry I cannot try to reproduce the problem now because I don't have
my capture hardware where I am.

Anyway, to return in topic: is AVI_IO able to see and capture from any
USB 2.0 tv boxes you are aware of?

TIA
Anonymous
June 2, 2004 7:31:11 PM

Archived from groups: rec.video.desktop (More info?)

On Tue, 01 Jun 2004 19:00:41 -0500, Rgb32 <Rgb32@yuv.com> wrote:

>Markus Zingg wrote:
>
>>>but in the past (with a bt878 pci card) I
>>>tried lots of programs like iuVcr, Avi_IO and many others,
>>
>>
>> Uhmmm, sorry to jump in here. AVI_IO will NOT get out of sync. If you
>> had the impression that it did, the problem is with playing back the
>> video.
>
>Nope, it DID get out of sync when I tried it.

Uhm no, not possible. Feel free to get in touch with me for me to let
me proofe it to you.

>Even if I set the slider at least 5 minutes away from the beginning, it
>was out of sync. I did not need to reach that position after a
>continuous playing (but even when I did that, it was the same result).

Again, if you were really trying this with AVI_IO and if you are not
confusing things with how you remember what was with what application
and resulting file and what not, your setup must have a problem with
playback.

>The total number of audio and video samples itself is not a guarantee
>that A/V will be in sync.

Well, belive me I'm really knowing what I'm talking about. No ofense
intended, but the above definition is correct. I'm of course refering
to capturing a video/audio stream - NOT to rendering existing footage
etc.

>VirtualDub duplicates or drops video frames in order to maintain sync
>(VirtualDubMod is even smarter: performs audio resampling on the fly and
>does not drop anything). What kind of algorithm is AVI_IO supposed to
>use for the enforcement of A/V sync?

AVI_IO duplicted or dropped frames as the first programm on this
planet for over a year up until Avery then implemented a similar
technology in VD. We were in touch back then and I still have the
e-mail traffic here to proofe it if needed. VD's audio resampling
filter came much later to the party and from what I know was written
by a german guy. Since AVI_IO does the droping/inserting in a still
unbeated fashion (whith the fewest corrections possible) I never saw a
compelling reason to implement audio resampling so far.

>I'm sorry I cannot try to reproduce the problem now because I don't have
>my capture hardware where I am.

ack.

>Anyway, to return in topic: is AVI_IO able to see and capture from any
>USB 2.0 tv boxes you are aware of?

AVI_IO here is in the same boat as VirtualDub in that it captures
through the Video for Windows API meaning you need a working VfW
driver or WDM wrapper. I can't tell wether this is available for the
device you are using or not.

Markus
!