question about RV10 Reference Picture Resampling

[E-Male]

i finally got some time to experiment some more with rv10
one option that got my attention is "Reference Picture Resampling"
if i understand it correctly it allows the encoder to resize the video for best quality
that would mean that i don't have to resize in avisynth anymore since the codec does that itself
right?

thx
E-Male

p.s. my tests seem to support my thought, but i wanna ask to make sure

[karl_lillevold]

Reference picture resampling means that if the codec detects that the bitrate is much too low for the chosen resolution and video complexity (bits/pixel too low), it will start downsizing frames and encode at a lower resolution. On playback, the decoder will detect the size change, decode at this lower resolution, and seamlessly upsample to the correct size on playback. In most cases, the switch should not be noticable for the viewer. The advantage is that you get less compression artifacts, but slightly blurrier video. Note that RPR is generally only used for very low bitrates. For the bitrates most users here are operating in, it will never kick in. In general it is still a good idea to use Avisynth to resize the video such that the enc. Here is table for which qualities you can expect for high action and certain bits/pixel numbers:

>= 0.225 : excellent
>= 0.175 : very good
>= 0.125 : good-medium
< 0.125 : medium-low

Unless you go far below 0.125, you will rarely see Reference picture take effect. Referece picture resampling can be disabled with a custom codec option. This is oftentimes desirable if you are using RealVideo to encode screen captures. These are often large resolution, but still very easy to encode.

[E-Male]

thx for the very detailed explaination

only few questiosn left:

-so RV10 isn't only VFR but also VR (variable resolution)?

-i assume thos B/P-valuies are for video with low grain, right?

-will RPR be triggeres just by certain fixed B/P-values or is also checked how many B/P the video needs? (i mean a grainy silent movie needs a lot more B/P then a pixar movie)

thx
E-Male

[karl_lillevold]

I guess you can say RealVideo is Variable Resolution, but like I mentioned, it will happen only at very very low bitrates relative to resolution.

The bits/pixel values above are probably for relatively low grain content. Compressing grain is like compressing random noise -- that is very hard. For this a pre-filter is recommended, and don't forget HFE2 on playback.

RPR is triggered partly based on B/P, but also other factors, that will take into account how hard it is to compress a certain video.

[bond]

is this feature the same as Reduced Resolution in MPEG-4?