DV Profile 8.1 HEVC: CBitstreamConverter::Convert errors → CAMLCodec 5s freeze cascades on T3b/p3i

[dizzysound]

Describe the bug

Periodic 1-second video stutters that occasionally escalate into 5-second frozen frames during playback of Dolby Vision Profile 8.1 HEVC content. Audio continues during the freeze; stop + restart resumes cleanly. Repeats on multiple DV P8.1 files. Reproduces on both NFS direct play and HTTPS direct play through Plex — not a transport issue. Same file plays cleanly when DV pipeline is bypassed via "Disable Dolby Vision support", confirming DV as the cause.

Log signature:

CBitstreamConverter::Convert: error converting.   (recurring during DV playback)
CAMLCodec::GetPicture: time elapsed since last frame: 5002ms (11:Resource temporarily unavailable)
OutputPicture - timeout waiting for buffer        (cascades in hundreds during a freeze)

Decoder open hints confirm DV path:

hdr type: dolbyvision
DOVI: version 1.0, profile 8, el type 0

Hypothesis: CBitstreamConverter (Kodi userspace, upstream of dovi.ko) fails on DV RPU NAL units (type 62) embedded in P8.1 streams. The failures starve the AMLogic decoder pipeline, which then hits its 5s decode_timeout_val. Bitstream errors don't always 1:1 cause a freeze — appears to be cumulative pressure.

How to reproduce

Steps to reproduce the behavior:

1. Configure CoreELEC for DV output (TV-Led or Player-Led — both reproduce).
2. Play a DV Profile 8.1 HEVC file. Example: a Netflix WEBDL such as ONE PIECE (2023) S01E01 — 2160p, DV HDR10, EAC3 Atmos, h265, ~20 Mbps.
3. Watch for ~10 minutes. Periodic 1s stutters appear; eventually 5s frozen-frame timeouts. Log shows CBitstreamConverter::Convert: error converting and CAMLCodec::GetPicture: time elapsed since last frame: 5001ms.

Information

• CoreELEC Version: 21.3-Omega_p3i_T3b_20260322020632
• Kernel: 4.9.269 #1 SMP PREEMPT Tue Mar 17 15:40:32 CET 2026 aarch64
• Hardware Platform: Amlogic T3b SoC
• Display: 4K DV-capable TV (HDMI VIC 93, 3840x2160p24)
• Player addon: script.plexmod (Plex for Kodi)
• Source path: HTTPS direct play through Plex Media Server (NFS direct play also reproduces)

Log file

Full Kodi log and Plex Media Server log for the affected session available on request — happy to upload to a paste service or attach. Key excerpts above.

Context

Things ruled out:

• Network/transport: reproduces on both nfs:// (libnfs) and https://...plex.direct:32400/library/parts/... (HTTP via Plex).
• File integrity: same bytes on re-read; same file plays cleanly to completion with DV disabled.
• Plex transcode: occurs on direct play; no transcoder involvement.
• DV LED mode: TV-Led and Player-Led both exhibit the issue. Player-Led if anything more aggressive (observed two 5s timeouts back-to-back).

Workaround that helps:

echo 5 > /sys/module/amdolby_vision/parameters/dolby_vision_mask

(Default is 7.) Persisted via /storage/.config/autostart.sh. Reduces stutter cadence noticeably. Cosmetic side effect: OSD/subtitles render with yellow tint during DV scenes.

Definitive but heavy fix: Settings → System → CoreELEC → "Disable Dolby Vision support" → ON. Falls back to the HDR10 base layer of P8.1 streams; eliminates the issue entirely. Confirms the DV pipeline as the cause.

Happy to test patches against this build.