some comments on my PAR and DAR experiments

[rekotc]

hi!.. i created a few video file to watch on my analog 4:3 PAL tv, im (still) trying to understand how PAR and DAR work.

i have a source video file with the following values:

SAR 2.35:1 1280x544
PAR 1:1
DAR 2.35

i created video1 with:
SAR 1,25 720x576
PAR 1.88
DAR 2.35

video2 with:
SAR 1,25 720x576
PAR 1
DAR 1,25

video3 with:
SAR 2.20 720x326
PAR 1
DAR 2,20

now, all the 3 files look the same to me on the tv (they all look squeezed in the same way). For what i understand, i know that the right PAR for PAL 4:3 is 16:15, in the first experiment (video1) i put some impossible PAR 1.88 that would theorically give the right DAR in output. In both video1 and video2 i use the maximum possible resolution, and it seems like the only possible PAR value is 16:15, so the player is ignoring the values i set for them?

in the 3rd video i used a different resolution so that in case the player uses PAR 16:15 i get 2.20*(16/15) = 2,35 which is the ratio of the original movie.

Sorry if im messing up but im trying to understand what's going on Could u explain me why the PARs are getting ignored?

thanks in advance

[jagabo]

What codecs, container, and player are you using? DVD only supports 16:9 and 4:3 DAR. Any source that isn't one of those must be letterboxed or pillarboxed before encoding.

[rekotc]

MPEG4 (xvid) and .avi file, it's a DVBT decoder that should handle any mpeg4 video stream.

[jagabo]

Are you sure the player supports PAR/DAR flags in Xvid AVI files? Your results would seem to indicate your player doesn't. For example, your first encoded file (720x576, PAR 1.88, DAR 2.35) should have displayed with black letterbox bars on a 16:9 TV, very large black letterbox bars on a 4:3 TV.

If your player doesn't support PAR/DAR flags you'll have to resort to square pixel encoding. Eg, 720x304 for 1 2:35:1 video.

[rekotc]

ok so i guess it doesnt handle PAR flags, i always see a full screen video no matter what i try to set. So just to understand better, if my player supports the PAR flag and i reencode the video to 720x304 and then i add black bars to it to reach 720x576, shouldnt the original video stream be still wrong with a PAR 16:15 ? i would get 720/304*(16/15) which is still different from 2.35. In that case i should resize it to 720x324 + black bars to 576 and PAR 16:15?

[jagabo]

If you resize and encode to 720x304 with square pixels the player should display it with the proper 2.35:1 aspect ratio by adding black bars itself. But some players don't even do that, they just display everything full screen. If your player stretches everything to full screen you'll have to add letterbox bars to whatever size your player requires to display the video properly.

But if you plan on watching more than a few videos I would recommend you just get a new player. Something like a Western Digital WDTV. It handles a wide variety of codecs and containers so you probably won't have to reencode anything. And it respects PAR/DAR flags in AVI, MKV, etc.

http://www.iboum.com/net-media-players.php

[Cornucopia]

Well, somewhere your math go messed up. PAL PARs are like this:

1. For a 4:3 DAR, using rec601 standard = 59:54, using MPEG standard = 12:11
2. For a 16:9 DAR, using rec601 = 118:81, using MPEG = 16:11

Try using the general equation: Horiz / Vert * PAR = DAR
Use it for each side of your source/target formula and only bring them together when an item on the source side equals an item on the target side.

For example, if your DARs are the same:

Horiz-source / Vert-source * PAR-source = Horiz-target / Vert-target * PAR-target

And solve for the missing variable(s).

BTW, NONE of your videos, including your source, are following any kind of standard.

Scott

[rekotc]

If you resize and encode to 720x304 with square pixels the player should display it with the proper 2.35:1 aspect ratio by adding black bars itself. But some players don't even do that, they just display everything full screen.

yes that seem to be my case, the player doesnt care about the aspect ratio, it streches everything!..so im trying to reencode using black bars, in this case i should feed him with a 720x304+black bars and i dont need to set any PAR or DAR since it doesnt read them, and i would instead use 720x324+black bars only if the player can later adjust the picture with the PAR of 16/15 ..right?
PAL PARs are like this:

1. For a 4:3 DAR, using rec601 standard = 59:54, using MPEG standard = 12:11
2. For a 16:9 DAR, using rec601 = 118:81, using MPEG = 16:11

mmm ...for what i know, if the source is 720x576 i need a PAR of 16:15 for a 4:3 DAR , while i should use a PAR of 12:11 only in case the source is 704x576, the resulting DAR is the same

[jagabo]

If you resize and encode to 720x304 with square pixels the player should display it with the proper 2.35:1 aspect ratio by adding black bars itself. But some players don't even do that, they just display everything full screen.

yes that seem to be my case, the player doesnt care about the aspect ratio, it streches everything!..so im trying to reencode using black bars, in this case i should feed him with a 720x304+black bars and i dont need to set any PAR or DAR since it doesnt read them, and i would instead use 720x324+black bars only if the player can later adjust the picture with the PAR of 16/15 ..right?

Probably not. It depends on exactly how your player stretches the video and what the aspect ratio of the final display (TV) is. If your final display is 4:3 I suspect you want to letterbox the 720x304 video to 720x540 or 720x544 (keeping a mod 16 height). If the TV is 16:9 then letterbox to 720x400 or 720x404. The exact value for 16:9 is 720x405 but odd values aren't allowed in Xvid. And sticking with integer multiples of 16 is best (400 = 16 * 25).

It's not likely your player is always assuming a DVD PAR or ITU D1 PAR when playing AVI files.

[rekotc]

ok i have the answer, the player has a menu where i can choose among 4:3 LB or PS and 16:9 LB and FIT, during my test it was set to 4:3 LB. It doesnt even try to read the PAR or DAR value from the file, once u set the value it's hardcoded in the player. I tried with a video containing just a circle 424x424 and i created 2 videos, one with a resolution 720x544 and PAR 1:1, the other with PAR 16:9.

The first video plays correctly if i select 4:3 LB from the player and the second is stretched.
If i select 16:9 LB i get the opposite result, the second video plays correctly.

so i dont have to rely on the PAR and DAR set in the files as the player ignores them.

yeah!... thanks for your help