Commit c3c35e94 authored by Derek Buitenhuis's avatar Derek Buitenhuis
Browse files

rate: Remove the max limit of reservoir_frame_delay



With the default max keyint of 10s, and common length fades found
in content, 256 frames is not sufficient to allow rate control
to adapt properly; it is barely even past the GOP boundary for
24 fps content.

This will introduce possible overflow problems with log_scale when
2-pass mode is introduced, if required.
Signed-off-by: default avatarDerek Buitenhuis <derek.buitenhuis@gmail.com>
parent c2440396
......@@ -394,6 +394,9 @@ pub struct RCState {
// The maximum buffer fullness (total size of the buffer).
reservoir_max: i64,
// The log of estimated scale factor for the rate model in Q57 format.
//
// TODO: Convert to Q23 or figure out a better way to avoid overflow
// once 2-pass mode is introduced, if required.
log_scale: [i64; FRAME_NSUBTYPES],
// The exponent used in the rate model in Q6 format.
exp: [u8; FRAME_NSUBTYPES],
......@@ -477,16 +480,14 @@ impl RCState {
framerate_den: i64, target_bitrate: i32, maybe_ac_qi_max: Option<u8>,
max_key_frame_interval: i32
) -> RCState {
// The buffer size is set equal to 1.5x the keyframe interval, clamped to
// the range [12, 256] frames.
// The buffer size is set equal to 1.5x the keyframe interval, with a minimum
// of 12.
// The interval is short enough to allow reaction, but long enough to allow
// looking into the next GOP (avoiding the case where the last frames
// before an I-frame get starved).
// The 12 frame minimum gives us some chance to distribute bit estimation
// errors in the worst case.
// The 256 frame maximum means we'll require 8-10 seconds of pre-buffering
// at 24-30 fps, which is not unreasonable.
let reservoir_frame_delay = clamp((max_key_frame_interval*3) >> 1, 12, 256);
let reservoir_frame_delay = ((max_key_frame_interval*3) >> 1).max(12);
// TODO: What are the limits on these?
let npixels = (frame_width as i64)*(frame_height as i64);
// Insane framerates or frame sizes mean insane bitrates.
......
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