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Video DC Restorer

In the old TVs, the PLL consisted of a monostable multivibrator set to run sightly lower than the expected line frequency. A signal edge assumed to be the H-sync pulse would retrigger the multivibrator a bit earlier before reaching the end of period. The voltage range was quite limited and so was the frequency locking so I do not see how that would burn the TV due to false sync pulses. The PAL, SECAM and NTSC line frequencies are quite close together, so you could get good H-sync, while the 50/60 Hz difference was often too much for V-sync.

Anyway, the H-sync pulse has an other important duty in OTA reception, since it is also used for generating the a.g.c. signal for the front end RF and IF stages at least in countries, with negative video modulation. The amplitude of the synch pulse is sampled and that value is then used for the _whole_ horizontal line. You can't use the average amplitude of the whole line as a.g.c., since the IF gain and hence average picture brightness would vary depending on picture content.

I have no idea, how they handled the a.g.c. in systems with positive video, such as the 405 line system in UK or 819 line system in France.

That was about 1980, such as the Salora/Nokia IPSALO

Reply to
upsidedown
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Probably like this...

Video_DC_Restorer_Keyed_Clamp_Tektronix.pdf

on the S.E.D/Schematics page of my website.

(I have all the old Tektronix manuals from 1968... used them so much the bindings fell apart... so I ran them thru my ibico binder ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

If you have the control logic inside the camera, where do you put the data storage? Won't you lose the data when you lose the camera? Most controlle r and storage are separated from the camera for this reason. If the camera s are getting too nice and valuable, thieves will be taking the camera rath er than what they are trying to protect.

Reply to
edward.ming.lee

a

a storage? Won't you lose the data when you lose the camera? Most control ler and storage are separated from the camera for this reason. If the came ras are getting too nice and valuable, thieves will be taking the camera ra ther than what they are trying to protect.

By the way, I am programming a Linux laptop to be a surveillant camera. I am capturing the image with "guvcview --no_display --exit_on_close -f jpeg

-c 1 -m 1", but it takes 3 seconds to take an image. I guess it's taking t oo long to open and close the camera port every time. I can use "-m huge_n umber" to get fast pictures, but it's keep overwriting the same image file.

What I need is to have output "-i image%d.jpg"? I hate to hack the program just for this.

Is there a better program to take sequential pictures faster?

Reply to
edward.ming.lee

t a

ata storage? Won't you lose the data when you lose the camera? Most contr oller and storage are separated from the camera for this reason. If the ca meras are getting too nice and valuable, thieves will be taking the camera rather than what they are trying to protect.

I am capturing the image with "guvcview --no_display --exit_on_close -f jpe g -c 1 -m 1", but it takes 3 seconds to take an image. I guess it's taking too long to open and close the camera port every time. I can use "-m huge _number" to get fast pictures, but it's keep overwriting the same image fil e.

am just for this.

seems you want tho opposite of this:

formatting link
ementation

-Lasse

Reply to
Lasse Langwadt Christensen

I am capturing the image with "guvcview --no_display --exit_on_close -f j peg -c 1 -m 1", but it takes 3 seconds to take an image. I guess it's taki ng too long to open and close the camera port every time. I can use "-m hu ge_number" to get fast pictures, but it's keep overwriting the same image f ile.

gram just for this.

crementation

Yes, according to the link, it is the behavior I want. But that's not happ ening to my version.

Reply to
edward.ming.lee

a. I am capturing the image with "guvcview --no_display --exit_on_close -f jpeg -c 1 -m 1", but it takes 3 seconds to take an image. I guess it's ta king too long to open and close the camera port every time. I can use "-m huge_number" to get fast pictures, but it's keep overwriting the same image file.

rogram just for this.

incrementation

ppening to my version.

OK, there is an "image_inc=X" option in .guvcviewrc. Non zero X would au to increment file name.

Reply to
edward.ming.lee

You want the cameras to be IP. I'm not so sure you want the storage there.

Reply to
miso

Most of these IP cameras act as web servers. So, you need to browse their internal image storages. They are rather expensive and more likely to be stolen. When that happen, you won't be able to get to the stolen pictures.

Reply to
edward.ming.lee

On a sunny day (Sun, 6 Jul 2014 16:31:21 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :

Yes, it is called recording a movie. If you look at the Linux soft on my site,

formatting link
it can record at any frame rate you like, so files do not have to be that big. I rotate files anyways every day, keep a couple of days tail. processor load is next to nothing if doing for example 2fps

26415 root 25 5 205m 30m 14m S 5.6 1.7 1:24.06 xine 4698 root 20 0 14744 9336 1492 S 5.3 0.5 4:08.62 mcamip
Reply to
Jan Panteltje

On a sunny day (Sun, 6 Jul 2014 16:31:21 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :

PS

Perhaps something like this script:

in one terminal type: mkfifo ffo

then type ffmpeg -f yuv4mpegpipe -i ffo -f avi -vcodec mpeg4 -b 1800 -g 30 -bf 2 -y q2.avi

In an other terminal type: mplayer tv:// -tv driver=v4l2:width=640:height=480:device=/dev/video0 -fps 2 -vo yuv4mpeg:file=ffo

This will create the mpeg4 file q2.avi

# mediainfo q2.avi complete name : q2.avi Format : AVI Format/Info : Audio Video Interleave File size : 332 KiB Duration : 1mn 56s Overall bit rate : 23.4 Kbps Writing application : Lavf54.6.100

Video Format : MPEG-4 Visual Format profile : Simple Streaming Video@L1 Format settings, BVOP : Yes Format settings, QPel : No Format settings, GMC : No warppoints Format settings, Matrix : Default (H.263) Codec ID : FMP4 Duration : 1mn 56s Bit rate : 22.6 Kbps Width : 640 pixels Height : 472 pixels Display aspect ratio : 4/3 Frame rate : 2.000 fps Resolution : 24 bits Colorimetry : 4:2:0 Scan type : Progressive Bits/(Pixel*Frame) : 0.037 Stream size : 321 KiB (97%) Writing library : Lavc54.23.100

Play with fps and bitrate. some versions of ffmpeg use different codecs, depends on what you compiled in. Some need thr bitrate in bits, some in kbits / second.

Write a script.

Reply to
Jan Panteltje

q2.avi

ideo0 -fps 2 -vo yuv4mpeg:file=ffo

But i am piping the data via GSM with 1G Bytes limit per month. So, video i s out of the question. I am pulling jpeg (640x480) and down convert into i con (128x96) and running fuzzy logic for motion detection. Although most o f the time it just detect light shadows, it captures people some of the tim e.

All the icon files are sent to the server, but the image files are only sen t upon request.

Reply to
edward.ming.lee

What does have to do with DC restoring? ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

What does this have to do with DC restoring? ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

On a sunny day (Mon, 7 Jul 2014 06:27:28 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :

mcamip has motion detection, but it only works for IP webcams, its function is to write to stdout in mjpegyuv format, that is what I wrote it for. in has on screen time too, and text as well.

For non IP sources mplayer can do almost anything from /dev/videoX. ffmpeg will resize to any size you like at any fps and any existing encoding. Type ffmpeg -codecs

Many of those other programs are based on ffmpeg (mplayer is for example).

To send it to a server use netcat pipe: ... | netcat IP PORT

netcat -u for UDP

You can listen to with netcat: netcat -l -p PORT | mplayer -

will play anything, audio, video...

Linux is about scripting the real tools, its power is there, pipes. At regular intervals people write some monster monolithic program from scratch that then cannot ever stand up to the power and flexibility of combining existing utilities in a script.

Best of luck with it.

Reply to
Jan Panteltje

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