The 1080p video at the same bitrate is also a lossy compression of the original 1080p, and the end result of decoding it will be an approximation of the original 1080p video that isn’t quite correct, because the exact same amount of information was thrown out.
That said, an ideal video encoding algorithm would always do better with a 1080p video because it has more options[1], but it’s not clear to me that actually-existing encoders meet this ideal.
If the optimal way to encode a video is to downscale it to 360p, an optimal 1080p encoder can downscale to 360p. If the optimal way to encode the video is to use information that’s not visible in 360p, the 1080p encoder can use it, but a 360p encoder can’t.
I mean, the ideal settings depend on content, use case and even personal preference when it comes to the details, so it’s probably not fundamentally possible to design an ideal video encoding algorithm that automatically produces the best possible video quality at the desired filesize without the need to manually finetune the settings. As long as we are manually finetuning the settings, the output resolution is one of the settings we can change, so in that sense, all the algorithms already implement that feature.
The 1080p video at the same bitrate is also a lossy compression of the original 1080p, and the end result of decoding it will be an approximation of the original 1080p video that isn’t quite correct, because the exact same amount of information was thrown out.
That said, an ideal video encoding algorithm would always do better with a 1080p video because it has more options[1], but it’s not clear to me that actually-existing encoders meet this ideal.
If the optimal way to encode a video is to downscale it to 360p, an optimal 1080p encoder can downscale to 360p. If the optimal way to encode the video is to use information that’s not visible in 360p, the 1080p encoder can use it, but a 360p encoder can’t.
I mean, the ideal settings depend on content, use case and even personal preference when it comes to the details, so it’s probably not fundamentally possible to design an ideal video encoding algorithm that automatically produces the best possible video quality at the desired filesize without the need to manually finetune the settings. As long as we are manually finetuning the settings, the output resolution is one of the settings we can change, so in that sense, all the algorithms already implement that feature.