16:9 .avi file doesnt fit the analog TV

[rekotc]

hi!, im experimenting a little with SAR PAR and DAR, but im still confused. I have an .avi file with the followings values:

SAR: 1.81 (640x352)
PAR: 0.98
DAR: 1.78 (16:9)

now, my tv is a 16:9 analog PAL, if i try to playback the video it doesnt show up correctly, the frames are cut on both left and right. Shouldnt it fit the screen since it has a DAR of 16:9?

thanks!

[Baldrick]

What do you play with? DVD Player? Computer directly connected to your tv? etc.

[jagabo]

Analog TV? It's probably overscanning the video.
https://www.videohelp.com/glossary?O#Overscan

[rekotc]

it's a DVB-T decoder, i use it for reading the file through the usb , its max supported resolution is 720x576, it's connected to my tv via a scart cable. How do i check if the tv is currently overscanning? i set the aspect on the tv to 16:9 but the problem is still there.

[yoda313]

If its analog shouldn't you set it to a letterbox mode? That should fix the bars so they don't get zoomed in.

Or is this a crt tube widescreen tv?

Edit - sorry didn't see you said it was a 16:9 tv. Yes jagabo is probably right it is most likely overscan.

You should have some sort of zoom option on the tv - at least lcd widescreen hdtvs do. Select either a 1:1 mode or some kind of "standard" or "normal" mode. It should read it as its originally encoded.

[rekotc]

ok something is wrong with the DVBT player, i think it resizes the video somehow. If i set the tv aspect to 4:3 i see black bars on the left and right but the image is still partially not visible, it's like if the input from the player to the tv differs in some way. I'll let you know if i find something else

[yoda313]

If i set the tv aspect to 4:3 i see black bars on the left and right but the image is still partially not visible,

Some dvd players have a 4:3 letterbox option. I would check this player to see if there is any kind of letterbox output. Ideally that should frame it properly without the vertical pillar bars.

Good luck.

[jagabo]

ok something is wrong with the DVBT player, i think it resizes the video somehow. If i set the tv aspect to 4:3 i see black bars on the left and right but the image is still partially not visible, it's like if the input from the player to the tv differs in some way. I'll let you know if i find something else

The TV is sumulating overscan. Because there's often junk at the edges of the frame. Broadcasters know that TVs overscan so they don't worry about junk at the edges of the frame. TV manufactures know there's often junk at the edges of the frame so they overscan. Or simulate overscan by cropping off the edges of the frame before displaying the video.

The only way to see the edges of the frame is to get a TV that doesn't overscan.

[rekotc]

ok i think i got something, i tried to record using the DVBT decoder on an usb key and then i analized the result. The video created by the recorder has the following values:

704x576
PAR 1.45
DAR 16:9

so, i tried to playback the video on the tv, the result is the same as for the other file, so i guess jagabo is right and the tv is overscanning on the edges even if it shouldnt be done in this case..

is it a possible answer?

[rekotc]

ok just to be sure, i uploaded the manual of my crt tv, http://www.2shared.com/document/LMocen0q/TQB8E3445eng.html could u please check page 8-9 to see if there is something i could do about the overscan? i guess no, but i'd like to hear from you

[jagabo]

The manaul isn't clear about overscan. All you can do is try the different settings.

It's likely everything you've ever seen on that TV has been overscanned. You've never noticed before because you didn't have an external reference to compare to. Why is it so important that this particular video not be overscanned?

There are likely only two things you can do to see the whole picture: buy a new TV with a non-overscan mode (many LCD HDTVs have this), or reencode the video with black borders around the edge so that the black borders are hidden by overscan, not the picture. But if you do that, be aware that the amount of overscan differs from TV to TV. So if you get it "perfect" for this TV it may not be for the next.

[rekotc]

ok thanks for the explanation, anyway i was just curious because i was sure about DAR 1.78 and then i noticed the cut along the edges, i tried different settings but i think you are right, everything i see on this tv is overscanned , if i select a different aspect and i move the central section of the picture i never reach the edges of the video, it's like if i can only select a portion of the overscanned picture and not the original not-overscanned. Anyway it's interesting to know but since this is my parents' tv set i dont care so much i just want them to watch their movies at the best possible quality

the idea of reencoding the video with black bars is not bad at all...i'll give it a try! thanks a lot for helping me out.

PS: there is something i dont understand about the PAR value, isnt it a standard value for a PAL video? can i set whatever value i need for getting the right DAR?

[jagabo]

PS: there is something i dont understand about the PAR value, isnt it a standard value for a PAL video? can i set whatever value i need for getting the right DAR?

It depends on the device you're using to play the file and the codec and container used. In theory, any frame size can represent any DAR using DAR or PAR flags. But some devices don't support PAR/DAR flags at all. Some may support some subsets. MPEG 2 only supports 4:3, 16:9, 2:11:1 DAR, and 1:1 DAR flags (DVD only the first two).

[rekotc]

so there is no "right PAR" for PAL? i've heard of 1.066 or 1.09..but i see all videos set it in different ways

[jagabo]

"PAL" is an analog system. It doesn't have pixels so it doesn't have a PAR until it's digitized. The PAR depends on what format that digital frame takes. For ITU D1 704x576 captures it is 16:11 for 16:9 DAR, 12:11 for 4:3 DAR. For 720x576 DVD frames it's 64:45 for 16:9 DAR, 16:15 for 4:3 DAR. But satellite broadcasts often come in different frame sizes. Like 480x576, 540x576, etc. Those will all have different PARs.

[rekotc]

now it's perfectly clear! thanks!