Is there anything wrong with using 640x360 as a resolution?

[MaximRecoil]

I was planning to encode a 16:9 MPEG-2 file to a 640x360 XviD AVI file, and I was wondering if the old rule about having the resolution be evenly divisible by 16 still applies? I am using Koepi's 1.1.2 build.

[celtic_druid]

If by rule, you mean compulsory, then no.

[MaximRecoil]

If by rule, you mean compulsory, then no.
Are there any advantages to using a resolution divisible by 16 and/or any disadvantages to using a resolution not divisible by 16?

[CWR03]

The main advantage to MOD-16 is compatibility with standalone players and other devices. If you plan on PC playback only, 640x360 is actually better as it's a true 16:9 resolution.

[celtic_druid]

For PC you can encode at any resolution though since non 1:1 PAR's aren't an issue. ie. you could use 640x368 with a PAR of 46:45.

[MaximRecoil]

Thanks for the replies. Since there is always the chance that I'll view my video files on my standalone XviD-compatible DVD player, I think I'll go with 624x352 just to be on the safe side. It isn't a true 16:9 resolution, but it is extremely close to it.

[henryho_hk]

Another suggestion: encode at 720x480 and set the pixel aspect ratio as "NTSC 16:9".

[CWR03]

Another suggestion: encode at 720x480 and set the pixel aspect ratio as "NTSC 16:9".
Unfortunately a lot of players don't recognize AR signaling. A lot of them will also balk at a 720x480 encode since the bitrate necessary to create a decent quality file will exceed their capabilities.

[henryho_hk]

That's too bad that SAP does not support AR signaling. I suggest MaximRecoil trying a short clip and see if it works in his player.

Actually, if his SAP plays "PC 1:1" as 1:1 on his NTSC TV, I think 720x400 is also a good choice (NTSC 16:9 is about 1.818:1 for PC monitor pixels) More information in http://www.mir.com/DMG/aspect.html

As for the bitrate, I have pretty good results in the range of 1500~1600kbps. How high the bitrate do you usually need for decent quality encode?

[raeltheimperialaerosolkid]

As for the bitrate, I have pretty good results in the range of 1500~1600kbps. How high the bitrate do you usually need for decent quality encode?

Let the codec decide the right bitrate. Set constant quantizer at 3 (if you are encoding animation from a good source) or 4 then make just 1 pass. Bitrate will be just fine.

[Chainmax]

You can also encode at 768x432 as it's only a ~50% increase over 624x352 and is a true 16:9 resolution. With some slight filtering (say, IVTC if possible, then RemoveGrain with mode=5 and/or FFT3DFilter with sigma=1), I agree with henryho_hk in that you could probably get decent results at ~1600kbps which most standalones should play effortlessly (don't most top at 4000kbps?).

[henryho_hk]

640x360 itself is not necessarily correct. For 4:3 NTSC DVD footage, we crop 720x480 to 704x480 and then resize to 640x480. Similarly, for 16:9, we crop it from 720x480 to 704x480 and then resize it to 640x360. If we omit the cropping step, the resize should be 640/704*720 ~= 656. Here, 656/360 ~= 1.82. Put it in another way. NTSC 4:3's pixel has a shape of 10:11 and that of 16:9 is 40:33. Therefore, the 16:9 display frame is actually of a shape of 40:33 * (720/480) ~= 1.82. Even more confusing is that, in the AV world, a square pixel is 768:767. Yet, a PC square pixel is really 1:1.

Taking all these into account, we have the following 2 approximations:

1) To resize a 4:3 (NTSC or PAL) DVD into PC video without cropping, the picture should be resized to a resolution of ratio 1.367:1.
2) To resize a 16:9 (NTSC or PAL) DVD into PC video without cropping, the picture should be resized to a resolution of ratio 1.823:1.

Remember that the ratios above are for uncropped pictures (720x480 or 720x576). To achieve our common resolutions (e.g., 640x480 or 720x400), we can perform either pre-cropping (need to adjust the ratios accordingly) or post-cropping (no need to adjust the ratios).

Well, how a SAP shows a PC square on the TV is another research topic.

[MaximRecoil]

640x360 itself is not necessarily correct. For 4:3 NTSC DVD footage, we crop 720x480 to 704x480 and then resize to 640x480. Similarly, for 16:9, we crop it from 720x480 to 704x480 and then resize it to 640x360. If we omit the cropping step, the resize should be 640/704*720 ~= 656. Here, 656/360 ~= 1.82. Put it in another way. NTSC 4:3's pixel has a shape of 10:11 and that of 16:9 is 40:33. Therefore, the 16:9 display frame is actually of a shape of 40:33 * (720/480) ~= 1.82. Even more confusing is that, in the AV world, a square pixel is 768:767. Yet, a PC square pixel is really 1:1.

Taking all these into account, we have the following 2 approximations:

1) To resize a 4:3 (NTSC or PAL) DVD into PC video without cropping, the picture should be resized to a resolution of ratio 1.367:1.
2) To resize a 16:9 (NTSC or PAL) DVD into PC video without cropping, the picture should be resized to a resolution of ratio 1.823:1.

Remember that the ratios above are for uncropped pictures (720x480 or 720x576). To achieve our common resolutions (e.g., 640x480 or 720x400), we can perform either pre-cropping (need to adjust the ratios accordingly) or post-cropping (no need to adjust the ratios).

Well, how a SAP shows a PC square on the TV is another research topic.
Oddly enough, with the NTSC DVD footage I am using for a source, it doesn't need cropping at all. It is the first DVD I have ever seen like this. The video goes all the way to the border on all sides as-is.

So are you saying that a 1.823:1 ratio would be more correct for PC video than a 1.77:1 ratio would be? If that is true, I might as well just go with 640x352 (1.818:1) while still having MOD-16.

[akupenguin]

Yes, theoretically NTSC 16:9 vids should use PAR=40:33, i.e. 704x480 frame. Nevertheless, some DVDs use the whole 720x480 frame, and need PAR=32:27 to look right (determined by measuring objects in the movie, so I know these numbers are right despite being not standard.)

[henryho_hk]

If that is true, I might as well just go with 640x352 (1.818:1) while still having MOD-16.

1.823:1 is for PC (and correctly tuned monitor) and I suggest you to encode a small clip and try it on your SAP and TV. Indeed, the difference between 1.823 and 1.778 is very small for me (esp. with the vertical and horizontal size controls on my monitor and my TV).

Two more useful websites:
1) the reference of my calculations: http://lipas.uwasa.fi/~f76998/video/conversion/
2) online calculator: http://www.haku.co.uk/ARCT.html

[SeeMoreDigital]

....If that is true, I might as well just go with 640x352 (1.818:1) while still having MOD-16.If you choose to generate your MPEG-4 encodes at this resolution, you could add aspect ratio signalling to the value of 44:45 to your MPEG-4 stream....

This value will correct the aspect ratio shape of your 1.8181:1 encode down to 1.7777:1 ;)


Cheers

[henryho_hk]

BTW, SeeMoreDigital, is this your homepage? http://www.seemoredigital.net/

[SeeMoreDigital]

BTW, SeeMoreDigital, is this your homepage? http://www.seemoredigital.net/Yes...