A (Most Likely) Dumb Question About Re-encoding Lossy Formats

[enter8]

If I'm re-encoding from 1080p h.264 to 480p h.264, that's lossy to lossy, right? So I'm taking a greater hit than just loss of pixels/resolution, correct?

How much data am I generally losing when I encode to 1080p h.264 and is it sufficient to make a considerable difference going down to 480p?

What about 4K? Is taking lossy 4K to 480p going to involve much of a hit in quality?

[smrpix]

Any time you reduce an image from 1/9th to 1/16th of its original resolution you can expect to lose some quality. If you're watching on a phone you may not see a lot of the difference.

[jagabo]

If I'm re-encoding from 1080p h.264 to 480p h.264, that's lossy to lossy, right? So I'm taking a greater hit than just loss of pixels/resolution, correct?

You will have losses from reducing the frame size and from the encoding. The encoding losses will depend on the settings you use -- anywhere from imperceptible to terrible.

How much data am I generally losing when I encode to 1080p h.264 and is it sufficient to make a considerable difference going down to 480p?

There will definitely be a difference in sharpness unless your 1080p video is very blurry (upscaled from 480p according to your other recent post?) to start with. If the source is sharp you're reducing each frame from 2073600 pixels to 408960 pixels -- so somethings gotta give.

What about 4K? Is taking lossy 4K to 480p going to involve much of a hit in quality?

The resolution losses are even worse.

As was pointed out, the resolution and size of the display you're viewing the video on will make a difference. watching a sharp 2160p video on a tiny 480p screen may not look any different that watching a 480p version of the video on that screen. But watching that 2160p video on a big 2160p screen will be much sharper than watching the 480p video.

[teodz1984]

if you are playing from a device with 480 native resolution, just make sure bitrate is high enough.. more action scenes higher bitrate..


just don't expect to get good results whwn play with hd devices..

[Cornucopia]

One good thing, though.
Assuming you viewed each NATIVELY (no scaling), lossy errors/artifacts and blockiness are minimized as the 1stgen encoder error is distributed among ~4 pixels (the amount of downscale). Not as good as a direct downscale & encode from a lossless source, but the next best thing.
Of course, who's going to be viewing the SD natively?

Scott