Live Digital video out of a camccorder

[markaren1]

Hi all,

Currently using a PVR-150 and S-video source, just wondering what is required to move all-digital.

Is it possible to get live MPEG2 video out of camcorder ?

I would like to buy a low cost unit, preferably with USB 2.0 (although I understand FireWire is/was the interface of choice) that has readily available drivers so a live camera would appear as /dev/videox under Linux.

Any pointers or experience appreciated.

Thanks,

Mark

[G4GUO]

The only thing I can think is that most cameras won't produce the low data rates needed for
DATV. That is the reason I have not tried it.

- Charles G4GUO

[G4GUO]

I have done a bit more work on this. Most consumer SD cameras use DV-DIF format
over their Firewire interface. Under Linux you can access the Firewire interface
using libiec61883/lib1394raw using the frame interface. Then using FFMPEG with
CODEC_ID_DVVIDEO you can turn the DV-DIF bitstream into a picture you
can then re-encode the picture using CODEC_ID_MPEG2 into an MPEG2
elementary stream which you can then turn into a program stream and
ultimately into a transport stream which you can then transmit using DVB-S.
I just got this working in my experimental DATV program using my Cannon XL1s,
video only at the moment sound will follow (when I can find the time). The DV-DIF
frames are a fixed length of 144000 bytes for PAL.

You can test whether your Firewire camera works under Linux using Kino
http://kinodv.org/ in capture mode. There is a separate set of libraries
for industrial Firewire cameras which use raw video. If you are using an HD camera
there is yet another interface format which I have not investigated.

- Charles G4GUO

[markaren1]

Well done Charles.

I guess for two hundred extra points, the final part of the question is "which is the lowest cost DV unit that provides live (E to E) video over fire-wire without switching itself off after some time out period"

Thanks for you help

Mark

PS how is DATV express progressing (maybe a separate thread) ?

[G4GUO]

Hello Mark,

I found that connecting the Firewire up to my JVC camcorder seemed to stop it switching itself off.
It looks like only SD cameras (those using the DV protocol) are supported by Linux at the moment.
Ultimately using a Webcam might be the way to go as FFMPEG can compress the raw video.

As far as DATVExpress is concerned there is an issue with the PLL part of the board which has been
fixed but can't be tested yet as I need to write some code to program the synth chip using I2C but
I am a bit too busy at the moment (with my O.U maths degree) and the hardware guy is not a
softie or a Linux user. We are using a Linux based cross compiler to do the firmware for the FX2 chip
because it is free.

I think I will probably add Digilite support to my Linux program sometime later in the year as it will
be fairly easy to do.

- Charles

[F6DZP]

Hello,

You will find here all the video sources I have tested in real time with Digilite - under Windows.

http://www.batc.org.uk/forum/viewtopic. ... t=10#p2941

You will see that DV input via firewire is easy to code in Mpeg2 and mux
HDV input via firewire is also possible but need a quad core (old 9550) to code Hd - H264 in real time.
Since I started DATV I have always used DV firewire input, I have ever thought it was the natural way of DATV producing.
DV is a very old standard now but firewire input is an easy way to get a not-analog video signal.

Newest camcorders with Mpeg2 output are more difficult to use because they produce Mpeg2 or H264 with very high rate for DATV, we are obliged to demux, to decode to recode, to remux ...
and sometimes use of a scaler to change the picture definition.

Last solution is to use HDMI output and use a card to capture and code in rel time the signal.

But we can have very good result with HD webcam that give RGB24 signal, better than an analog composite input from a camera.
no need to demux, decode.. This solution is cheap and give very good results.

Jean Pierre F6DZP

[G4GUO]

Hello Jean Pierre,

Have you had time to add support for DVB-S2 to Tutioune yet?

I wrote a DVB-S2 transmit protocol stack last year but I have no
way of testing it at the moment.

I tried interfacing with the Technotrend card on my Linux machine.
I can get it to receive DVB-S but when I tell it to switch to S2 the
program locks up. So I am still looking for something that will decode
S2 at low symbol rates.

- Charles G4GUO

[F6DZP]

Hi Charles,
I have not work for DVB-S2 decoding, as they are not very much DVB-S2 transmit solutions.
Last evolution with Tutioune is the ability to work/decode H264.
H264 is a first important step.
I think we will get more switching from Mpeg2 to H264 than switching DVB-S to DVB-S2.
HD video 1920x1080 can be sent at SR 500 or lower if we use H264.( Ihave upload an exemple in the Digilite part of the Forum)
So I first explore those possibilities to use low rate down to SR 300 before regarding DVB-S2.

This morning I have tested my Webcam C525 in real time Mpeg2 coding with a very little motherboard with Atom525.
it can code up to 1024 x 576p at 30 fps (80%CPU)
And when I code in real time with this webcam, 640x480 at 30 fps, send it to Digilite, I can at same time with the same CPU use Tutioune for measuring/decoding and showing video (80%CPU)
That allow to have a full DATX TX/RX that can be very little and plug on 12v for mobile use.


Jean Pierre F6DZP

[G4GUO]

Hello Jean Pierre,

I had a play with H.264 about a year ago and it is definitely an improvement on MPEG2.
My experiments with H.264 were using DVB-T rather than DVB-S so I did not try any low
speed stuff. I just fed the signal into a standard terrestrial HDTV and even though I
was not using DVB-T2 it decoded fine.

Very few chipsets seem to support DVB-S2 at low symbol rates. The Technotrend one does
but S2 is poorly supported by the Linux driver. Looks as if I will have to get the Linux code
to work then. Another job for the list.

- Charles