fix: skip disposable pictures during local seek preroll

Checks/local-seek.mm

@@ -0,0 +1,68 @@
+// Exercise the real local seek/decode/presentation loop without worker races.
+#include "../Sources/Core/player.cpp"
+#include <cstdio>
+#include <cstdlib>
+
+static void require(bool condition, const char *message) {
+    if (!condition) { std::fprintf(stderr, "FAIL: %s\n", message); std::exit(1); }
+}
+static std::vector<uint8_t> pixels(const AVFrame *frame) {
+    const auto format = static_cast<AVPixelFormat>(frame->format);
+    const int size = av_image_get_buffer_size(format, frame->width, frame->height, 1);
+    require(size > 0, "preview has readable pixels");
+    std::vector<uint8_t> bytes(size);
+    require(av_image_copy_to_buffer(bytes.data(), size, frame->data, frame->linesize,
+        format, frame->width, frame->height, 1) == size, "copy preview pixels");
+    return bytes;
+}
+
+
+int main(int argc, char **argv) {
+    require(argc > 1, "provide local media fixtures");
+    for (int i = 1; i < argc; ++i) {
+        av_log_set_level(AV_LOG_ERROR);
+        Player player;
+        player.shutdown();
+        player.stopping.store(false);
+        player.activeEpoch = player.requestedEpoch.load();
+        player.open(Command{Action::Open, argv[i]});
+        require(player.tracks[1].codec && player.canSeek, "seekable local video");
+        player.output.set_volume(0);
+        for (bool playing : {false, true}) {
+            for (double fraction : {.01, .79, .21, .59}) {
+                const double target = player.duration * fraction;
+                // Full reference decoding supplies an independent expected picture,
+                // including disposable B-frames at or immediately after the target.
+                player.seek(target, false);
+                VideoFrame expected{};
+                const auto referenceStart = Clock::now();
+                while (!expected.frame && Clock::now() - referenceStart < std::chrono::seconds(5)) {
+                    player.decodeOne(true);
+                    while (!player.video.empty()) {
+                        auto frame = std::move(player.video.front());
+                        player.videoBytes -= frame.bytes;
+                        player.video.pop_front();
+                        if (frame.pts + sampleTime * .5 >= target) {
+                            expected = std::move(frame);
+                            break;
+                        }
+                    }
+                }
+                require(bool(expected.frame), "full decode supplies reference picture");
+                const auto start = Clock::now();
+                player.seek(target, playing);
+                while ((!player.presented.frame || player.presented.pts < target - .002) &&
+                       Clock::now() - start < std::chrono::seconds(5))
+                    player.tick();
+                const double elapsed = std::chrono::duration<double, std::milli>(Clock::now() - start).count();
+                std::printf("local-seek fixture=%s playing=%d target=%.3f preview=%.3f latency_ms=%.3f\n",
+                    argv[i], playing, target, player.presented.pts, elapsed);
+                require(player.presented.frame && player.presented.pts == expected.pts &&
+                        pixels(player.presented.frame.get()) == pixels(expected.frame.get()),
+                        "seek presents the exact fully decoded picture, including B-frame targets");
+                require(player.status == (playing ? PLAYER_PLAYING : PLAYER_PAUSED),
+                        "seek preserves playback intent");
+            }
+        }
+    }
+}

Makefile

@@ -143,7 +143,18 @@ $(BUILD_DIR)/seek-queue-check: Checks/seek-queue.cpp Sources/Core/player.cpp Sou
 check-seek-queue: $(BUILD_DIR)/seek-queue-check
 	$(BUILD_DIR)/seek-queue-check
 
-check: check-dependencies $(BUILD_DIR)/playback-check check-seek-queue check-video-decoding check-fixtures check-audio check-window check-config check-youtube check-quality check-adaptive check-network check-progress check-reporting check-cli check-runtime check-media check-startup check-bundle check-subtitles check-resolved check-cast check-queue
+$(BUILD_DIR)/local-seek-check: Checks/local-seek.mm Sources/Core/player.cpp Sources/Core/player.h Sources/Core/player_macos.h Sources/Core/output.hpp Sources/Core/video_decoder.hpp Sources/Core/network_input.hpp Sources/Core/network_policy.hpp Sources/Core/progress_reporter.hpp $(filter-out $(BUILD_DIR)/player.o,$(OBJECTS)) Makefile | check-dependencies
+	$(CXX) $(CXXFLAGS) $< $(filter-out $(BUILD_DIR)/player.o,$(OBJECTS)) $(FF_LIBS) $(FRAMEWORKS) -o $@
+
+$(BUILD_DIR)/fixtures/local-seek.mp4: Makefile | check-dependencies
+	mkdir -p $(BUILD_DIR)/fixtures
+	ffmpeg -hide_banner -loglevel error -y -f lavfi -i testsrc2=size=1920x1080:rate=30:duration=12 -f lavfi -i sine=frequency=440:sample_rate=48000:duration=12 -c:v libx264 -preset ultrafast -threads 2 -bf 2 -g 300 -keyint_min 300 -sc_threshold 0 -c:a aac $@
+
+.PHONY: check-local-seek
+check-local-seek: $(BUILD_DIR)/local-seek-check $(BUILD_DIR)/fixtures/local-seek.mp4 $(DECODE_FIXTURES)
+	$(BUILD_DIR)/local-seek-check $(BUILD_DIR)/fixtures/local-seek.mp4 $(DECODE_FIXTURES)
+
+check: check-dependencies $(BUILD_DIR)/playback-check check-seek-queue check-local-seek check-video-decoding check-fixtures check-audio check-window check-config check-youtube check-quality check-adaptive check-network check-progress check-reporting check-cli check-runtime check-media check-startup check-bundle check-subtitles check-resolved check-cast check-queue
 	$(BUILD_DIR)/playback-check $(BUILD_DIR)/fixtures
 
 check-fixtures: | check-dependencies

README.md

@@ -154,7 +154,7 @@ Settings load once at startup. Menu changes are session-only and never write the
 ## Limits
 
 - SDR output only; PQ/HLG HDR is rejected. No stream playlists, playlist-file import, embedded/YouTube captions, manual audio-track selection, rotation, or deinterlacing. The session-only local-file queue and external resolved-source WebVTT subtitles are supported.
-- H.264, HEVC, and VP9 prefer VideoToolbox decoding with software fallback; other codecs, including AV1, use software. Backward frame stepping can be slow on long-GOP or unindexed media.
+- H.264, HEVC, and VP9 prefer VideoToolbox decoding with software fallback; other codecs, including AV1, use software. Local seeks remain frame-accurate: disposable non-reference pictures strictly before the target are skipped, but reference pictures still require decoding. Seeking and backward frame stepping can remain slow on long-GOP or unindexed media.
 - Network buffering is bounded and memory-only; live/non-seekable sources disable seeking and frame stepping. Expired stream URLs are not automatically refreshed.
 - Audio-device changes during playback are not handled.
 
@@ -169,6 +169,8 @@ The full suite requires a graphical macOS session and a working audio device; it
 
 The startup checks verify that playing video remains attached, unhidden and sized to its native drag surface, including with the queue open; playback-state checks alone do not establish renderer visibility.
 
+`make check-local-seek` measures paused/playing local seek-to-picture latency and compares the resulting timestamps and pixels against full decoding, including B-frame targets. It covers a 1080p H.264 long-GOP file with audio and the six hardware/software decoder fixtures; timing is diagnostic, not a machine-dependent pass threshold.
+
 Queue-open resize checks require positive native resize increments and exercise continuous horizontal/vertical resize-delegate sequences, including reversals, to preserve video aspect without snap-back. The driving axis is fixed for each live resize gesture so aspect corrections do not feed back into axis selection. Physical edge-drag resizing still needs manual verification.
 
 `make benchmark-playback` measures cold source startup, cached/uncached seeks, and sustained native/Cast playback with repeatable loopback fixtures. It requires the same macOS session/audio device and fixture-generation FFmpeg; results exclude live extraction, WAN/TLS, and physical-receiver latency.

Sources/Core/player.cpp

@@ -468,6 +468,7 @@ struct Player {
         for (auto &track : tracks) {
             if (!track.codec) continue;
             avcodec_flush_buffers(track.codec);
+            track.codec->skip_frame = AVDISCARD_DEFAULT;
             track.drainSent = track.drained = false;
             track.firstPacket = true;
             av_packet_unref(track.packet);
@@ -1151,6 +1152,17 @@ struct Player {
                           "Preparing video decoder preroll");
                     track.firstPacket = false;
                 }
+                if (slot == 1) {
+                    // Preroll needs reference pictures, not disposable pictures before
+                    // the target. Restore full decoding before the target packet and
+                    // for exact frame stepping; never guess when timestamps are absent.
+                    const auto *packet = track.packet;
+                    const bool preroll = !network && !stepping && !previewShown && seekTarget > 0 &&
+                        packet->pts != AV_NOPTS_VALUE &&
+                        packet->duration > 0 &&
+                        (double(packet->pts) + packet->duration) * av_q2d(track.stream()->time_base) - origin < seekTarget;
+                    track.codec->skip_frame = preroll ? AVDISCARD_NONREF : AVDISCARD_DEFAULT;
+                }
                 const int result = avcodec_send_packet(track.codec, track.packet);
                 if (result != AVERROR(EAGAIN)) {
                     check(result, "Sending media packet to decoder");

TODO.md

@@ -6,6 +6,7 @@
     - multi-file Open/Finder/drop, natural filename order, editable queue sidebar, explicit append, previous/next and automatic advance; Cast navigation retains the receiver; UI/drag-drop and physical-Cast verification remain unverified
 - [x] make sure the `make install` command installs the application (i can't find it in spotlight)
     - installs to ~/Applications, migrates the old hidden app, registers with Launch Services and requests Spotlight indexing; actual install, CLI, code signature, registration and Spotlight query passed; Spotlight UI remains unverified
-- [ ] takes an awfully long time seek in local videos which i find weird, since seeking in streamed youtube videos is pretty much instant
+- [x] takes an awfully long time seek in local videos which i find weird, since seeking in streamed youtube videos is pretty much instant
+    - local seek preroll skips disposable non-reference pictures without sacrificing exact target frames; measured 1080p/10-second-GOP paused seek improved from 541 ms to 400 ms and playing seek from 682 ms to 488 ms; timestamp/pixel checks passed across six decoder formats; long-GOP reference decoding remains necessary, and the originally affected files still need manual verification
 - [ ] in the "choose what to play" screen, we should change the youtube button to general streaming
 	- we can figure out the stream and how to handle it from the url (i.e. if youtube url, handle as youtube stream; if miruro url, handle accordingly)