Zero-stutter 8K loops on Tizen 6.5

Goals & constraints

Zero frame drops at 8K (7680×4320) and typical frame rates (29.97/30/50/59.94/60 fps).
Seamless loop points with no black frame, audio click or rebuffer.
Local playback with offline cache by default and optional network fallback.
Operational reliability with checksums, watchdogs and crash-safe update flow.

1) Mastering the encode

For Tizen 6.5 class signage/TVs, we recommend HEVC (H.265) for 8K masters. Use constant frame rate, closed GOPs and a conservative bitrate aligned to the visual complexity of your content.

Audio track

For silent loops, include a very low bit rate AAC or no audio at all to avoid priming noise.
For music, use AAC-LC 128–192 kbps at 48 kHz and ensure perfect cut points (see Looping).

ffmpeg reference encode (HEVC 8K @60 fps, visually complex):

ffmpeg -y -r 60 -i input_8k_master.mov \
  -c:v libx265 -preset slow -pix_fmt yuv420p10le \
  -x265-params "level=6.2:high-tier=1:vbv-bufsize=120000:vbv-maxrate=120000:hrd=1:keyint=120:min-keyint=120:no-open-gop=1:bframes=3" \
  -b:v 100M -maxrate 120M -bufsize 120M -r 60 \
  -c:a aac -b:a 160k -ar 48000 -ac 2 \
  -movflags +faststart -video_track_timescale 60000 \
  output_8k60_hevc.mp4

Why these flags? Closed GOPs and a fixed key-interval keep decoder state predictable at the loop. VBV and HRD prevent bitrate spikes that can cause SoC frame drops. +faststart places moov at the head for instant prep.

2) Muxing for gapless loops

Ensure the file begins on an IDR keyframe and ends exactly before the next GOP.
For AAC, avoid encoder delay clicks at the seam by aligning audio to frame boundaries and trimming padding.

# frame-accurate, keyframe-aligned loopable segment
ffmpeg -i output_8k60_hevc.mp4 -ss 00:00:00.000 -to 00:02:00.000 \
  -c copy -avoid_negative_ts make_zero loop_2min.mp4

# if you hear an audio tick at the seam, re-encode audio only with exact length
ffmpeg -i loop_2min.mp4 -c:v copy -af "atrim=0:120,asetpts=N/SR/TB,apad=pad_dur=0" loop_2min_audiofix.mp4

3) Files, caching & checksums

Pre-cache the loop locally (internal storage) and verify integrity with a checksum.
Keep a shadow file and swap with a temp name to avoid partial-write crashes.
Store a small .json manifest beside the file with sha256, byte size, duration, fps and last verification timestamp.

// sample manifest (loop_2min_audiofix.mp4.manifest.json)
{
  "filename": "loop_2min_audiofix.mp4",
  "sha256": "<digest>",
  "bytes": 158734003,
  "duration_s": 120.000,
  "fps": 60,
  "verified_at": "2025-08-01T10:00:00Z"
}

4) Tizen app (AVPlay) setup

In a Tizen web app, use tizen.tvavplay (AVPlay) for local file playback. Below is a minimal pattern that prepares, plays and restarts on ended without visual gaps. Pin a display rectangle and add watchdogs for resilience.

const avplay = tizen.tvavplay;
const LOOP_PATH = 'wgt-private/loops/loop_2min_audiofix.mp4';

function prepareAndPlay() {
  try {
    avplay.open(`file://${LOOP_PATH}`);
    avplay.setDisplayRect(0, 0, screen.width, screen.height);
    avplay.setDisplayMethod('PLAYER_DISPLAY_MODE_FULL_SCREEN');
    avplay.setTimeoutForBuffering(5 * 1000); // local files: keep small

    avplay.setListener({
      onbufferingstart: () => console.log('buffering...'),
      onbufferingcomplete: () => console.log('buffered'),
      onevent: (type, data) => console.log('event', type, data),
      onstreamcompleted: () => {
        avplay.seekTo(0, () => avplay.play());
      },
      onerror: e => {
        console.error('AVPlay error', e);
        restart();
      }
    });

    avplay.prepareAsync(() => avplay.play());
  } catch (e) {
    console.error('prepare failed', e);
    setTimeout(restart, 2000);
  }
}

function restart() {
  try {
    avplay.stop();
    avplay.close();
  } catch (_) {}
  prepareAndPlay();
}

document.addEventListener('visibilitychange', () => {
  if (document.visibilityState === 'visible') {
    try {
      avplay.play();
    } catch (_) {}
  }
});

prepareAndPlay();

Not all firmwares expose identical AVPlay options; keep the loop logic in your app layer so it behaves consistently across minor versions.

5) Looping without gaps

Video: closed GOP, keyframe at start, exact trim so the last frame ends just before the next GOP.
Audio: for music, ensure no encoder delay — trim/pad precisely. If silent, omit audio.
Player: handle onstreamcompleted → seekTo(0) → play() immediately.
UI: render overlays in separate layers; avoid layout thrash at loop boundaries.

6) Soak testing & telemetry

Run a 72-hour soak with device telemetry: frame-drop counters, CPU/GPU temperature, free storage.
Power-cycle and network-bounce during the test; validate auto-recovery and manifest re-verification.
Export a proof-of-play CSV with start/stop timestamps per loop and device heartbeat.

FAQs & quick fixes

Q: I see a single black frame on repeat.
A: Your loop likely cuts mid-GOP. Re-trim on a keyframe or reduce GOP to 1 s to simplify alignment.

Q: There's an audio click at the loop.
A: Re-encode audio with exact duration (no encoder delay), or omit audio for art loops.

Q: Playback stutters after 30–60 min.
A: Lower max bitrate (VBV), reduce B-frames and verify your local cache/storage speed and file integrity.