1916 vs 1920

[evlo]

Hello,

i wonder why are some rips in 1916 and not in 1920 resolution? Why is that?

[LoRd_MuldeR]

1916 % 16 != 0, but 1920 % 16 == 0 ;)

In other words: Keeping it at 1920 should be preferred, because 1920 is mod16, while 1916 is not!

But the loss in compression efficiency caused by Non-mod16 resolution isn't that big. So you shouldn't worry too much about it.

Cropping down to 1916 was probably done to remove the border ???

[roozhou]

@MuldeR
You are wrong again this time!!
1080 isn't mod16 either, but both HDTV and BD keep it.

If the video has 2 pixels of black border on both sides, it is better to crop them for compression efficiency. Smart encoders like x264 will pad with the last column(you should know this) while without cropping you have to encode the black bars and the sharp edges cost more bitrate(you should also know this).

The real problem is once you want to view such 1916 video on a FullHD screen, you may need to scale it. A lot of players on PC have an option to view videos in full screen at the original resolution so this problem can be easily avoided.

[LoRd_MuldeR]

@MuldeR
You are wrong again this time!!
1080 isn't mod16 either, but both HDTV and BD keep it.

1080 isn't mod16, obviously. But I was discussing 1920 -vs- 1916. So what I said is perfectly correct! :mad:

If the video has 2 pixels of black border on both sides, it is better to crop them for compression efficiency. Smart encoders like x264 will pad with the last column(you should know this) while without cropping you have to encode the black bars and the sharp edges cost more bitrate(you should also know this).

If there are black bars, yes!

But in the general case encoding non-mod16 resolutions hurts compression (not too much though) and thus should be avoided. That's exactly what I explained in the post above.

Reading before replying is what helps :rolleyes:

[roozhou]

But in the general case encoding non-mod16 hurts compression (not too much though) and thus should be avoided.

Reading before replying is what helps :rolleyes:
We should no longer warn people about "non-mod16 hurts compression"(x264 has already removes the "compression will suffer" warning). People uses non-mod16 resolution only when they don't want black bars or cropped non-black pixels and keep the correct aspect ratio.

Here are some situation for example:

1) 1920x1080 with 2 pixels on both left and right. Cropping them to 1916 helps compression instead of hurting compression.
2) 704x480 @ 16:9. You want 1:1 sar. The closest mod2(required by 4:2:0) resolution is 854x480, but many rippers will scale it to 848x480(or scale to 854x480 and crop to 848x480) because they are told "non-mod16 hurts compression". Actually they just trade correct AR(or visible pixels) for a litte bitrate.