[Cin] offtopic: Digitize and record Video with A/D USB adapters

Marco Ciampa ciampix at posteo.net
Tue Oct 12 08:44:16 CEST 2021

On Tue, Oct 12, 2021 at 01:24:43AM +0200, Terje J. Hanssen via Cin wrote:
> Den 11.10.2021 22:41, skrev Marco Ciampa via Cin:
> > Hello people,
> > first time I'm writing here and not native English speaker.
> > So forgive me if I'm not that good at expressing myself.
> > 
> > That said I want to share the content of an article I read somewhere that
> > (unfortunately) I do not remember anymore but I remember the guts of if
> > and think it could be much useful for someone.
> > 
> > The writer tested a lot of (not so) inexpensive PAL/NTSC USB and PCI
> > converters and a few of expensive ones too. Suddenly he remembered that
> > its Digital TV with PAL/NTSC input was _much_ better at displaying video
> > that the video grabbers. To make a long story short he discovered that
> > that was because of an internal analog to digital _and_ the FHD to HD
> > digital downconverter that did the trick. The principle here is "always
> > sample much more that what you want to obtain".
> > 
> > The result is this: forget the explensive and inexpensive grabbers and
> > buy:
> > 
> > - one cheap HDMI to USB3 grabber (you can find models compatible with
> >    linux for ~10-20 euros / dollars)
> > 
> > - one cheap PAL/NTSC (SCART) to HDMI converter (you can find models for
> >    ~10 euros/dollars)
> > 
> > and that's all. It will also come handy for aquisition of video from
> > reflex/mirrorless cameras and so on...
> > 
> > Hope someone find this handy...
> > 
> > --
> > 
> > Saluton,
> > Marco Ciampa
> This looks like a captivating, simple solution, if and when everything work.
> What I think I've read previous, is that playback of interlaced video looks
> better on Televisions than on PC displays.
> 1. My TV has built-in ports for analog video playback (S-Video and
> RCA/Phono), beside additional SCART and HDMI ports

Yes but unfortunately these are _inputs_ and cannot be used for
conversion from analog video to digital video. The converter is _inside_
the TV and unfortunately, you cannot use it.
But the thing is that chip is very inexpensive and you can find it in
SCART to HDMI converters.

> 2. If I understand your description right, the HDMI to USB3 grabber should
> be used to record from a TV HDMI port to a Linux PC?

No. The HDMI to USB3 must be feeded by a cheap (but effective) analog to
digital converter.

The thing is: the analog to digital converters _and_ the digital grabbers
inside cheap pal/ntsc to usb2 are a crap. If you want a really good
quality conversion you have to open wide your wallet and buy a really
expensive grabber just to be sure that it has inside a good (but not so
expensive in itself) analog to digital converter. 

... or use a cheap external one like this (just an example):


and to capture use one of these:


these are just examples, (I do not work for Amazon! ;-) I picked them
randomly and they _SHOULD_ work, but I cannot be 100% sure, never tried
those in particular... it is just to explain the principle of this
method... that you should give it a go... it's not such a great expense.

Please note that if you want a pass through usb video grabber (useful for
example to grab games) you have to spend a bit (5xtimes!) more for a
device with input _and_ real time output.

> While my HDV camera supports HDMI video out, I wonder if TV HDMI ports do
> that as I have really never tested it.

The camera does output, the TV only INPUT. No luck.

> (At least my HD PVRK could not record HDTV via the HDMI cable, only a
> limited format from the antenna cable. Analog VCR could record SD video via
> SCART or S-video adapter)

Yes of course.

> 3. If HDMI video out works, what type of digital signal is expected (format
> uncompressed and chroma level?)?

HDMI output works only through adapters, see above..

> And if works, it has to be recorded as compressed  (lossless) on the Linux
> PC? Among other 4:3 aspect ratio from analog SD video has to be taken care
> of.

One usually grabs with maximum quality one can afford and only _after_
grabbing thinks about compression. That is the way to preserve much of
the original quality.


Marco Ciampa

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