Thread: Recording TV with camera

There's only one other route that comes to my mind, and even that is totally speculative stuff I *might* be able to do sometime in the future. Argh!
What I'm thinking is I'd like to get the braodcasted signal to my computer by, like, attaching a cable from TV and convert it realtime to digital form and write an avi.

To the experienced people here...is what I'm planning of doing actually possible?

Edit:
I might not be able to do it even if it's possible but I'm still curious. I know TV gets the broadcasted data through a cable attached to it. Is it possible to get the signal from it directly to a computer without any intervening "box"?

Originally Posted by Elysia

So that leaves my question unanswered: if the source is 30 fps, then why bother with interlacing if bandwidth was not an issue?

Originally Posted by phantomotap

I find it strange that you can apparently conceive of the costs of overcoming bandwidth limitations in the existing infrastructure as being a factor, yet you can imagine no other limitations of the time that would have informed the decisions made during development.

Originally Posted by Elysia

Whatever then >_<

From the wikipedia entry on Interlaced Video (first phrase): "Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth."

And this is why wikipedia is not always a good source. Or, when it is, it pays to actually read the whole article.

Interlaced video was introduced back then, not because really of bandwidth limitations. These limitations actually didn't exist. You could produce high frame rate videos as far back as the 80s. The problem was that bandwidth was (still is, just in a less amount) directly tied the price of the equipment in the production chain. That is video bandwidth isn't just a matter of buying fatter cables. It actually affects everything in the production chain, from recorders to displays.

Instead the real reason why interlaced video was introduced was because there were no known methods for compression, transport of compressed video signal through the analogue pipeline, and decompression at the customer end. These methods already existed for digital video.

The digital video signal goes as far back as the 70s. But it only became commercially viable in the 90s. The nature of the signal permits compression and this is why interlaced video is no longer a viable option.

Originally Posted by the_jackass

There's only one other route that comes to my mind, and even that is totally speculative stuff I *might* be able to do sometime in the future. Argh!
What I'm thinking is I'd like to get the braodcasted signal to my computer by, like, attaching a cable from TV and convert it realtime to digital form and write an avi.

To the experienced people here...is what I'm planning of doing actually possible?

Edit:
I might not be able to do it even if it's possible but I'm still curious. I know TV gets the broadcasted data through a cable attached to it. Is it possible to get the signal from it directly to a computer without any intervening "box"?

Yes, it is possible. You take the cable with your video and plug it into a capture card in your computer or some external recorder.
Now comes the tricky part, of course. What kind of video cable is it? Coaxial? RCA? Component? S-Video? HDMI? DVI?
I'm not sure where your source comes from.

It's a normal coaxial cable AFAIK.

Then you will need a capture card with a "TV" input as they're typically called, or at least were some years ago. You would plug your cable directly into your capture card, boot up your capture software and away you go.

I'll have to see if capture cards are available in my small city. Going out and buying something was the last thing I'd wanted to do. Though if I dont get this thing where I live/within cash, I'll atleast try to get a good normal video camera.Neither of which are going to happen in the near future.Well anyways thanks for the suggestion cuz I hadnt known about video capture cards before.

You know that there's something called "internet," too, right? You can buy stuff online these days if there something that's not in your local neighborhood. Just be sure to do proper research before buying one (if you do, of course).

Originally Posted by Elysia

I don't know how it was back then, when interlacing was introduced, but I mean, today, 30 is much different from 60, depending on source.
I take it interlaced has something to do with the frequency of the voltage from the outlet. Therefore, if the source is 30, they would have to somehow "extend" it to 50/60. It still doesn't make sense, though, as they could just duplicate frames. So that leaves my question unanswered: if the source is 30 fps, then why bother with interlacing if bandwidth was not an issue?

Your question is good - bandwidth was an issue.

The NTSC standard for video allowed 4.5 Mhz bandwidth (analog). To display the video with full resolution with progressive scanning would require 30 fps (frames per second), and that is 30 progressive frames per second. The amount of flicker present would be unacceptable. Without increasing the bandwidth, the frame rate could not be increased. So the frame rate was kept the same, but divided into two fields, one containing the even numbered scan lines, and one containing the odd. This doubles the flicker rate from 30 Hz to 60 Hz. (see my last post about movie film projection flicker) The interlacing process itself did not change bandwith requirements. For a given frame rate, it would be the same, whether progressive or interlaced. What interlacing did was to allow a higher (and unnoticable) flicker rate.

The bandwidth of NTSC transmissions was based on limitations of receiving circuitry and the need to fit some number of channels into the commercial TV transmission band. Interlacing was adopted instead of higher frame rate.

I just recalled an early attempt at adding information digitally to the bottom of TV images. This wasn't a digital transmission, but was information added digitally to the picture. The horizontal lines in the graphics, especially, had an annoying flicker. Interlacing does not work well when components of the image reside exclusively in only one field of the frame. They are there for one field, then gone in the next, then back again in the next; this repeats 30 times a second and is quite noticable. This is also why the early interlaced computer monitors never caught on. A line of pixels would reside on only an even scan line or an odd one, and would noticably flicker as the even and odd fields alternated.

The 60 Hz power line frquency was also a factor in selecting the field rate. It was very difficult to remove power supply "ripple" from the TV receiver circuitry. This ripple showed up in the picture, but was unnoticable as long as it was motionless. Matching the field frequency to the linefrequncy removed the motion. This ripple manifests as a very slight warping of the picture. It can be seen in color broadcasts on CRT sets, since the field rate is 59.94 Hz. The ripple passes through the picture once every 16 seconds approximately

-

There's sum good news. I recorded from my dad's TV (which has a glass "magnifier" frame in front of it) and all the interlacing issues are gone. I think the glass frame has got something to do with it. The phase problems are still there, but much reduced. I think experimenting a bit with it's brightness, color and contrast settings will kill this issue as well. Cool.

edit:
But yeah the PSP copying problems are still there. And wtf! it's making the first 8 bytes of the files 'USBC86(' even while copying. (And chaging stuff after that too...no riff chunk identifier in sight in the first 512 bytes). Here's a sample of the bullcrap:

Code:

file length = 105522816 (0x64a2680)

----------------------------------------------------------------------------------
             00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f      0123456789abcdef
----------------------------------------------------------------------------------
00000000     55 53 42 43 38 36 28 82 00 10 00 00 80 00 0c 28      USBC86(........(
00000010     00 00 28 f4 c8 00 00 08 00 00 00 00 00 00 00 00      ..(.............
00000020     09 89 05 00 0a 89 05 00 0b 89 05 00 0c 89 05 00      ................
00000030     0d 89 05 00 0e 89 05 00 0f 89 05 00 10 89 05 00      ................
00000040     11 89 05 00 12 89 05 00 13 89 05 00 14 89 05 00      ................
00000050     15 89 05 00 16 89 05 00 17 89 05 00 18 89 05 00      ................
00000060     19 89 05 00 1a 89 05 00 1b 89 05 00 1c 89 05 00      ................
00000070     1d 89 05 00 1e 89 05 00 1f 89 05 00 20 89 05 00      ............ ...
00000080     21 89 05 00 22 89 05 00 23 89 05 00 24 89 05 00      !..."...#...$...
00000090     25 89 05 00 26 89 05 00 27 89 05 00 28 89 05 00      %...&...'...(...
000000a0     29 89 05 00 2a 89 05 00 2b 89 05 00 2c 89 05 00      )...*...+...,...
000000b0     2d 89 05 00 2e 89 05 00 2f 89 05 00 30 89 05 00      -......./...0...
000000c0     31 89 05 00 32 89 05 00 33 89 05 00 34 89 05 00      1...2...3...4...
000000d0     35 89 05 00 36 89 05 00 37 89 05 00 38 89 05 00      5...6...7...8...
000000e0     39 89 05 00 3a 89 05 00 3b 89 05 00 3c 89 05 00      9...:...;...<...
000000f0     3d 89 05 00 3e 89 05 00 3f 89 05 00 40 89 05 00      =...>...?...@...
00000100     41 89 05 00 42 89 05 00 43 89 05 00 44 89 05 00      A...B...C...D...
00000110     45 89 05 00 46 89 05 00 47 89 05 00 48 89 05 00      E...F...G...H...
00000120     49 89 05 00 4a 89 05 00 4b 89 05 00 4c 89 05 00      I...J...K...L...
00000130     4d 89 05 00 4e 89 05 00 4f 89 05 00 50 89 05 00      M...N...O...P...
00000140     51 89 05 00 52 89 05 00 53 89 05 00 54 89 05 00      Q...R...S...T...
00000150     55 89 05 00 56 89 05 00 57 89 05 00 58 89 05 00      U...V...W...X...
00000160     59 89 05 00 5a 89 05 00 5b 89 05 00 5c 89 05 00      Y...Z...[...\...
00000170     5d 89 05 00 5e 89 05 00 5f 89 05 00 60 89 05 00      ]...^..._...`...
00000180     61 89 05 00 62 89 05 00 63 89 05 00 64 89 05 00      a...b...c...d...
00000190     65 89 05 00 66 89 05 00 67 89 05 00 68 89 05 00      e...f...g...h...
000001a0     69 89 05 00 6a 89 05 00 6b 89 05 00 6c 89 05 00      i...j...k...l...
000001b0     6d 89 05 00 6e 89 05 00 6f 89 05 00 70 89 05 00      m...n...o...p...
000001c0     71 89 05 00 72 89 05 00 73 89 05 00 74 89 05 00      q...r...s...t...
000001d0     75 89 05 00 76 89 05 00 77 89 05 00 78 89 05 00      u...v...w...x...
000001e0     79 89 05 00 7a 89 05 00 7b 89 05 00 7c 89 05 00      y...z...{...|...
000001f0     7d 89 05 00 7e 89 05 00 7f 89 05 00 80 89 05 00      }...~...........

Until the 512th byte (and till much later too) all files are having this exact same data.

Why the ........ is my PSP doing this crap?

Looks like some header they put on there for whatever reason. Ours is not to wonder why... ours is to figure out how to strip that crap off of there

It's not happening in all AVI files. Or sometimes it's initially a normal AVI file (with RIFF tag and whatnot) and it magially changes to this USBC crap while being copied.

As for it being a header, well it seemingly changes the full file cuz files that take longer than a certain time in copying get some of the data in their end corrupted (VLC freezes on a frame when it's at that point and continues showing that frame until the end of seeking.)

If anyone has any idea how to fix these your help will be much appreciated.

If anyone has any idea how to fix these your help will be much appreciated.

O_o

Your memory stick is corrupted, becoming corrupted, or possibly dying for good.

You can try to repair the file system to buy you enough time to pull any remaining data, but you should probably replace the stick as soon as possible.

Soma

It's not a memory stick, it's an ancient PSP with a USB cable.

edit:
Although there's some chance it might be chinese stuff.

It's not a memory stick, it's an ancient PSP with a USB cable.

O_o

The original PSP only had a few MiB of internal storage.

You are saving files to external storage.

The external storage is a memory stick.

The USB connection is just a view of the memory stick.

Soma