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VideoCacheThread: add directional preroll

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- start cache rebuilds with a preroll offset (settings-based)
- tighten isReady to require frames ahead/behind playhead add unit tests for preroll clamping and readiness
This commit is contained in:
Jonathan Thomas
2026-02-05 12:39:06 -06:00
parent 47b308122f
commit 43f9ed89ae
4 changed files with 124 additions and 5 deletions
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57
src/Qt/VideoCacheThread.cpp
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@@ -29,6 +29,7 @@ namespace openshot
, last_speed(1)
, last_dir(1) // assume forward (+1) on first launch
, userSeeked(false)
, preroll_on_next_fill(false)
, requested_display_frame(1)
, current_display_frame(1)
, cached_frame_count(0)
@@ -56,7 +57,11 @@ namespace openshot
return true;
}
return (cached_frame_count > min_frames_ahead);
int dir = computeDirection();
if (dir > 0) {
return (last_cached_index >= requested_display_frame + min_frames_ahead);
}
return (last_cached_index <= requested_display_frame - min_frames_ahead);
}
void VideoCacheThread::setSpeed(int new_speed)
@@ -112,10 +117,15 @@ namespace openshot
Timeline* timeline = static_cast<Timeline*>(reader);
timeline->ClearAllCache();
cached_frame_count = 0;
preroll_on_next_fill = true;
}
else if (cache)
{
cached_frame_count = cache->Count();
preroll_on_next_fill = false;
}
else {
preroll_on_next_fill = false;
}
}
requested_display_frame = new_position;
@@ -138,6 +148,39 @@ namespace openshot
last_cached_index = playhead - dir;
}
void VideoCacheThread::handleUserSeekWithPreroll(int64_t playhead,
int dir,
int64_t timeline_end,
int64_t preroll_frames)
{
int64_t preroll_start = playhead;
if (preroll_frames > 0) {
if (dir > 0) {
preroll_start = std::max<int64_t>(1, playhead - preroll_frames);
}
else {
preroll_start = std::min<int64_t>(timeline_end, playhead + preroll_frames);
}
}
last_cached_index = preroll_start - dir;
}
int64_t VideoCacheThread::computePrerollFrames(const Settings* settings) const
{
if (!settings) {
return 0;
}
int64_t min_frames = settings->VIDEO_CACHE_MIN_PREROLL_FRAMES;
int64_t max_frames = settings->VIDEO_CACHE_MAX_PREROLL_FRAMES;
if (min_frames < 0) {
return 0;
}
if (max_frames > 0 && min_frames > max_frames) {
min_frames = max_frames;
}
return min_frames;
}
bool VideoCacheThread::clearCacheIfPaused(int64_t playhead,
bool paused,
CacheBase* cache)
@@ -242,6 +285,7 @@ namespace openshot
int64_t timeline_end = timeline->GetMaxFrame();
int64_t playhead = requested_display_frame;
bool paused = (speed == 0);
int64_t preroll_frames = computePrerollFrames(settings);
cached_frame_count = cache->Count();
@@ -269,9 +313,16 @@ namespace openshot
}
// Handle a user-initiated seek
bool use_preroll = preroll_on_next_fill;
if (userSeeked) {
handleUserSeek(playhead, dir);
if (use_preroll) {
handleUserSeekWithPreroll(playhead, dir, timeline_end, preroll_frames);
}
else {
handleUserSeek(playhead, dir);
}
userSeeked = false;
preroll_on_next_fill = false;
}
else if (!paused && capacity >= 1) {
// In playback mode, check if last_cached_index drifted outside the new window
@@ -316,7 +367,7 @@ namespace openshot
// If paused and playhead is no longer in cache, clear everything
bool did_clear = clearCacheIfPaused(playhead, paused, cache);
if (did_clear) {
handleUserSeek(playhead, dir);
handleUserSeekWithPreroll(playhead, dir, timeline_end, preroll_frames);
}
// Compute the current caching window