Buffer overflow with fade from black

[Former user]

Encoding a video with a fade from black using a constant bitrate (strict requirement) creates a buffer overflow issue when decoding.

x265 options: strict-cbr=1 bitrate=32000 vbv-maxrate=32000 vbv-bufsize=32000 vbv-init=0.1 hrd=1 aud=1 repeat-headers=1 keyint=24 min-keyint=1 bframes=3 no-open-gop=1

Buffer and bits per frame graphs attached. The spike in the buffer occurs during the fade from black and notice also the lack of data in the bits per frame analysis graph.

[Deepthi Nandakumar]

Hello,

Do you mean that x265 did not notify you of a buffer overflow, but the decoder did? That would be a serious error - can we have access to the video used here so we can replicate this?

We're working on a related issue, handling fade-ins and fade-outs better inside ratecontrol. There is a related patch on scene cut detection/transitions that will detect this so that better frame QPs can be assigned.

Deepthi

[Deepthi Nandakumar]

slicetype: Modify Scenecut algorithm to detect scene transition points to improve Rate Control (refs #160).

identify scene trasitions, fade-ins, fadeouts, sceneCuts and signal the flag bSceneCut in Lowres structure. This flag will be used by RateControl to adjust the wps during scene cuts.

→ <<cset 4992f0384252>>

[Steve Borho]

we believe this is resolved, please re-open if your testing finds further problems.