[SOLVED] resize an mkv for a 16:9 tv

[rekotc]

hello everybody, im trying to convert an .mkv video with resolution 1280x534 (DAR 2.40?) for a CRT tv with a 16:9 panel. This file has to be converted to .avi since it's the only available format for the player connected to the tv. The player can handle up to 720x576 xvid ASP@5 resolution (this is what i got from the manual). Im not an expert so forgive my stupid question, if i dont want the video to be letterboxed, i should resize the video to 720x405, in this way i get a 1,78 DAR and no black stripes on the TV...right? But if i do so, i get a squeezed video on the horizontal resolution...is there any way i can resample the original video to get both a 16:9 stream and the right proportions?

thanks in advance

[Baldrick]

You must crop the sides then.

[rekotc]

thanks for your fast answer! mmm...ok so i should cut some unwanted parts from the original mkv in order to get 720x405 and the right proportiions? just trying to understand better.

[Baldrick]

Well, they might not be unwanted...so it always best to leave it as 2.40:1 if you want the entire image.

What do you convert with now? Most good converter should be able to crop video.

[rekotc]

ah ok so i keep it 2.40:1, anyway i downloaded a few programs and now im getting used to virtualdub, in this case i have to crop the converted .avi since i cant open an mkv using virtualdub.

thanks for all the info!

[rekotc]

ok i still cant get the wanted result, i decided not to crop the original mkv, so i resized the video to 720x404 with a PAR 1.0. I thought i was going to get a full screen video on my tv but i still have 2 black bars, thinner than the ones i got before but not a full screen. Why ? I thought i created a 16:9 video stream.

thanks for your help!

[neomaine]

With all due respect, you should get used to the 'black bars'.

[rekotc]

it's not a problem for me, im simply trying to learn something i thought i was going to create a 16:9 video but it doesnt seem so ...so im asking just for understanding better, i dont care so much if the black bars are still there, but i want to understand why!

thanks

[jagabo]

ok i still cant get the wanted result, i decided not to crop the original mkv, so i resized the video to 720x404 with a PAR 1.0. I thought i was going to get a full screen video on my tv but i still have 2 black bars, thinner than the ones i got before but not a full screen. Why ? I thought i created a 16:9 video stream.

Post a sample of your final file. Nobody can see what you're doing so there's no way to say what's wrong.

[rekotc]

ok thanks, here it is a sample.

[jagabo]

It looks like you encoded it right (although since you resized the entire 1280x534 frame down to 720x404 everything is horizontally squished -- but that's apparently what you wanted). You're using a DVD player to play the video on your 16:9 HDTV? You probably have the player or TV set up wrong. What type of cable are you using? HDMI? Composite? Is it an upscaling player? I suspect the player is set to output 4:3 and the TV is set to stretch 4:3 to 16:9. You want the player to output 16:9 and the TV to keep that AR.

[rekotc]

Ok there is a setup problem i guess, i tried to load a standard dvd with the dvd player (which is different from the player i use for .avi files) and on the same tv i see it with the same black boxes...so the tv has to be setup i guess.

[rekotc]

ok i realized that the .avi player has some strange behaviour (this crappy model: http://www.dikom.it/en/prodotti-dvbt/dvbt_135SCART.html ). I tried to record directly from the tv using this player, and it recorded an .mpg file that can be played at full screen. Using mediacoder on the file i got the following specs:

resolution: 720x576
aspect ratio (16:9)
pixel aspect ratio 1.42

i dont understand where does the 16:9 aspect ratio come from, considering it is 720x576 (1.25) with PAR 1.42 (no idea why)

thanks for your help

[jagabo]

resolution: 720x576
aspect ratio (16:9)
pixel aspect ratio 1.42

i dont understand where does the 16:9 aspect ratio come from, considering it is 720x576 (1.25) with PAR 1.42 (no idea why)

Any size frame can be displayed in any final shape. Pixels don't have to be square. MPEG streams have the display aspect ratio flagged in the headers. So even though the frame is 720x576 (5:4) the AR flag says to display it as 16:9.

[rekotc]

ok but from what i know i should have SARxPAR = DAR, in this case SAR = 720/576, PAR = 1.42 and DAR = ....1.78 (16:9) ??

[jagabo]

ok but from what i know i should have SARxPAR = DAR, in this case SAR = 720/576, PAR = 1.42 and DAR = ....1.78 (16:9) ??

Yes. Note that MPG flags only supports 3 DARs and one SAR: 4:3, 16:9, 2.21:1 DAR, and 1;1 SAR.

[rekotc]

thanks!, sorry if i look stupid ...i tried to calculate it and i got something different from DAR = 1.78 so i was having problems understanding Now i have the right result 1.25*1.42 = 1.775 ...

Yes. Note that MPG flags only supports 3 DARs and one SAR: 4:3, 16:9, 2.21:1 DAR, and 1;1 SAR.

but if SAR can be only 1:1 how can i have a file with a 720x576 ? shouldnt it be like 500x500 or 720x720 or anything like SIZExSIZE ?

[jagabo]

Yes. Note that MPG flags only supports 3 DARs and one SAR: 4:3, 16:9, 2.21:1 DAR, and 1;1 SAR.

but if SAR can be only 1:1 how can i have a file with a 720x576 ? shouldnt it be like 500x500 or 720x720 or anything like SIZExSIZE ?

The flag has only 4 possible values equating to 4:3, 16:9 or 2.21:1 DAR (meaning whatever the frame size, display the final picture at the specified DAR) or 1:1 PAR (display the picture the same shape as the SAR). You can only specify one flag.

[rekotc]

ah ok, thanks again. So in conclusion...since the .mpg created by the video player itself is working right at 16:9 with a frame resolution of 720x576 and PAR 1.42, i should convert my .avi using the same parameters?

[rekotc]

ok i think i definitely got it, in order to obtain a PAL widescreen i need to use a PAR of 1.42 (teorically 1.45). This value was calculated as the optimal value for showing PAL anamorphic wide screen, considering that analog TV screens dont have a vertical resolution but the analog signals are resampled creating non-square pixels with a resolution of 720x576 .

this is what i got from googling around for an hour, now i think i have it clear

thanks for your help!

[rekotc]

ok the .avi file 720x576 + PAR 1.42 still shows black bars, while the .mpg doesnt, i dont know what to think now.

[jagabo]

ok the .avi file 720x576 + PAR 1.42 still shows black bars, while the .mpg doesnt, i dont know what to think now.

Your player, like many, doesn't support Xvid PAR/DAR flags properly.

[rekotc]

Your player, like many, doesn't support Xvid PAR/DAR flags properly.

ok...i will try to convert it to mpg and see if it can handle the flags correctly in this last case! So this means that maybe the first .AVI file i made with a 720x405 resolution and PAR 1.0 was correct?

thanks..im going to sleep!

[jagabo]

It sounds like the file you originally made was fine. Except many player will not play a Xvid file with an odd frame width or height -- in this case 405. you should always use mod4 (integer multiples of 4) at least. Mod8 and Mod16 are even more compatible and efficient.

[rekotc]

ok using an MPG container and mpeg2 codec keeping 720x576 PAR 1.42 it shows up correctly

thanks jagabo!

[jagabo]

Note that with MPEG 2 you are specifying the DAR, not the PAR. I've seen a few DVD players that had problems playing bare MPG files with the correct DAR (ie, the need a full VIDEO_TS, IFO/VOB structure).

[rekotc]

you are right, i had to set the DAR not the PAR, anyway it worked!

[jagabo]

The difference between setting the PAR and the DAR is important when you are cropping a video. Say you have a 2.35:1 movie encoded on a 16:9 DVD. If you leave the frame at 720x576 and encode with the 16:9 DAR flag the video will display properly. But if you crop away the black borders, leaving a 720x432 frame, and encode that with a 16:9 DAR flag it will display incorrectly -- because the correct DAR is now 2:35:1, not 1.78:1. On the other hand, when using codecs that support PAR you can use the same PAR (1.42 in this case) for both videos because cropping the border has no effect on the shape of the remaining pixels.

[rekotc]

mmm this further explanations made a little of confusion in my mind, why the correct DAR is 2.35:1 if i crop the video?