How to modify uMaxPictureSize? impdbg doesn't work

[mesvam]

I'm trying to increase this value

chnAttr->rcAttr->CappedQuality->uMaxPictureSize = 1920(0x780) offset:size = 72:4

but impdbg --enc_rc_s 0:72:4:4000 seems to have no effect. Does anyone know how to "unlock" this value?

On first glance, one may assume this is the video resolution but it actually affects max bitrate. The resolution is specified by uWidth and uHeight, and the documenation for uMaxPictureSize says this

用于限制编码一帧后最大码流大小，建议设置为uMaxBitRate 大小

Which I have translated to

Used to limit the maximum bitstream size after encoding one frame, it is recommended to set it to the size of uMaxBitRate

This seems to specify a maximum size of each frame, independent of other bitrate and quality constraints, such that the final bitrate can never be higher than uMaxPictureSize kbps. (i.e. uMaxPictureSize/FPS = max kilobytes per frame, which is enforced for every frame, even if the instantaneous bitrate is lower than uMaxBitRate) The default value is locked to 1920, forcing a maximum bitrate of ~2000kbps, even if uMaxBitRate is higher.

Additionally, if the average bitrate is close to 2000kbps, the video appears to stutter every uGopLength frames; the quality goes waaay down for a few frames when it encodes an I-frame, which needs more bytes to encode properly, but due to uMaxPictureSize we are bit starved