v0.4.11: video frame ring buffer + decoder stats + 0.1s audio buffer

0.4.10 still played at ~2-5 fps even though the decoder buffer was
preallocated. Root cause: the single-slot staging buffer was paced by
SourceDataLine backpressure at the audio buffer's granularity (~0.5 s),
so the decoder burst-produced ~12 video frames into the slot while audio
drained, the consumer saw only the last frame of each burst, then the
decoder stalled until audio drained again. Net visible rate ~ source_fps
/ frames_per_burst.

Fix:
- Replace single staging slot with a 4-slot ring (preallocated, FIFO).
  Decoder writes to ringTail; if full, overwrites oldest and bumps
  droppedFrames so we can see overflow in the log. Render thread drains
  oldest under the same lock — no allocation, no race.
- Shrink audio driver buffer 0.5 s → 0.1 s so the decoder is paced more
  tightly. Burst size collapses from ~12 frames to 2-3, which fits
  inside the ring.
- Log decoder spec on start (WxH @ fps, audio Hz x ch, ring depth) and
  produced/consumed/dropped counters every ~10 s. Lets the user log
  confirm whether the decoder is keeping real-time pace and whether the
  ring is overflowing.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -3,7 +3,7 @@
 마인크래프트 안에서 임의의 동영상 URL을 벽·바닥·천장에 평면으로 재생하는 Fabric 모드.
 
 - 모드 ID: `video_player`
-- 현재 버전: **0.4.7**
+- 현재 버전: **0.4.11**
 - 마인크래프트 버전: **26.1.2**
 - 필요 Java: **25** (마인크래프트 26.x 가 요구함)
 
@@ -51,91 +51,23 @@ Fabric은 마인크래프트에 모드 기능을 추가해 주는 로더입니
      https://cdn.modrinth.com/data/P7dR8mSH/versions/Sy2Bq7Xc/fabric-api-0.149.0%2B26.1.2.jar
    - 더 최신 빌드를 찾을 땐: https://modrinth.com/mod/fabric-api/versions → 페이지에서 게임 버전 필터 `26.1.2` 를 직접 선택. (URL 파라미터 필터가 듣지 않는 경우가 있어서 페이지 안에서 한 번 더 확인하는 게 안전합니다.)
    - 받은 `fabric-api-0.149.0+26.1.2.jar` 를 `mods` 폴더에 넣습니다.
-2. **video_player** (이 모드)
+2. **video_player** (이 모드, 0.4.11 부터 JavaCV 가 jar 안에 포함됨)
    - 다운로드: https://git.tkrmagid.kr/tkrmagid/mc_video_player_mod/releases
-   - `video_player-0.4.7.jar` 를 다운로드해서 같은 `mods` 폴더에 넣습니다.
+   - 자신의 OS·CPU 에 맞는 jar **한 개** 만 받아서 `mods` 폴더에 넣으면 됩니다 (별도 JavaCV 설치 불필요):
+     - Windows 64bit: `video_player-windows-x86_64-0.4.11.jar` (~32MB)
+     - macOS Intel: `video_player-macosx-x86_64-0.4.11.jar` (~24MB)
+     - macOS Apple Silicon (M1/M2/M3/M4): `video_player-macosx-arm64-0.4.11.jar` (~21MB)
+     - Linux 64bit: `video_player-linux-x86_64-0.4.11.jar` (~27MB)
+   - 자기 OS 가 헷갈리면: Windows 는 거의 다 `windows-x86_64`, 인텔맥은 `macosx-x86_64`, 애플 실리콘 맥은 `macosx-arm64`, 리눅스는 `linux-x86_64`.
 
-이전 버전(`video_player-0.4.0.jar`, `0.4.2.jar`, `0.4.3.jar`, `0.3.x.jar` 등)이 mods 폴더에 남아있다면 **반드시 삭제**하세요. 두 개가 같이 있으면 마인크래프트가 충돌로 켜지지 않습니다.
+이전 버전(`video_player-0.4.0.jar`, `0.4.2.jar`, `0.4.3.jar`, `0.3.x.jar` 등)이 mods 폴더에 남아있다면 **반드시 삭제**하세요. 두 개가 같이 있으면 마인크래프트가 충돌로 켜지지 않습니다. 0.4.7 이하에서 쓰던 JVM 인수(`-Xbootclasspath/a:...javacv...`) 도 0.4.11 부터는 **빼주세요** — 모드 jar 안에 같은 JavaCV 가 들어있어서 부트클래스패스의 것과 충돌해 검은 화면이 날 수 있습니다.
 
-### STEP 5. 영상 재생 라이브러리 (JavaCV) 설치
+### STEP 5. 잘 설치됐는지 확인
-
-여기까지만 하면 마인크래프트는 켜지지만, 영상 자리에 검은 판만 보입니다. 진짜 영상을 재생하려면 **JavaCV** 라는 디코더 라이브러리가 필요합니다.
-
-> 솔직한 안내: 마인크래프트 공식 런처는 mods 폴더에 들어있는 일반 라이브러리 jar를 자동으로 읽어 주지 않습니다. 그래서 JavaCV 설치 절차가 조금 번거롭습니다. 가장 쉬운 길과 공식 런처에서 동작시키는 길 두 가지를 안내합니다.
-
-#### 5-A. 가장 쉬운 길: Prism Launcher 로 갈아타기 (선택)
-
-공식 런처 대신 무료 오픈소스 런처인 **Prism Launcher** 를 쓰면 클릭 몇 번으로 JavaCV를 라이브러리로 추가할 수 있습니다. 게임 자체는 같고, 정품 마인크래프트 계정으로 로그인하는 것도 동일합니다.
-
-1. https://prismlauncher.org/download/ 에서 다운로드 → 설치
-2. Prism에서 인스턴스 → 마인크래프트 26.1.2 + Fabric Loader 0.19.2 선택해서 생성
-3. 인스턴스 우클릭 → **Edit** → 왼쪽의 **Version** 탭 → **Add to Minecraft.jar** 버튼
-4. 아래 STEP 5-B 의 1번 항목에서 받은 JavaCV jar 5개를 한꺼번에 선택해서 추가
-5. **Launch** 로 실행
-
-이 방법이 가장 안정적이고 빠릅니다.
-
-#### 5-B. 공식 런처에서 동작시키기
-
-공식 런처를 계속 쓰고 싶다면 아래 절차를 따르세요.
-
-1. **JavaCV 1.5.13 다운로드**
-   - 다운로드 링크: https://github.com/bytedeco/javacv/releases/download/1.5.13/javacv-platform-1.5.13-bin.zip (2026-02-22 릴리스, FFmpeg 8.0.1 동봉)
-   - 압축을 풀고 `javacv-platform-1.5.13-bin` 폴더 안에서 **다음 jar 5개**를 골라 둡니다 (다른 파일은 안 씁니다):
-     - `javacv.jar`
-     - `javacpp.jar`
-     - 자신의 OS에 맞는 **javacpp 네이티브 jar** (이게 빠지면 검은 화면 — JNI bridge `jnijavacpp` 로딩에 꼭 필요):
-       - Windows 64bit: `javacpp-1.5.13-windows-x86_64.jar`
-       - macOS Intel: `javacpp-1.5.13-macosx-x86_64.jar`
-       - macOS Apple Silicon (M1/M2/M3/M4): `javacpp-1.5.13-macosx-arm64.jar`
-       - Linux 64bit: `javacpp-1.5.13-linux-x86_64.jar`
-     - `ffmpeg.jar`
-     - 자신의 OS에 맞는 **ffmpeg 네이티브 jar**:
-       - Windows 64bit: `ffmpeg-8.0.1-1.5.13-windows-x86_64.jar`
-       - macOS Intel: `ffmpeg-8.0.1-1.5.13-macosx-x86_64.jar`
-       - macOS Apple Silicon (M1/M2/M3/M4): `ffmpeg-8.0.1-1.5.13-macosx-arm64.jar`
-       - Linux 64bit: `ffmpeg-8.0.1-1.5.13-linux-x86_64.jar`
-
-2. **이 5개 jar 를 게임이 읽도록 등록**
-   - 가장 안전한 위치: `.minecraft/libraries/javacv/` 폴더를 새로 만들고 5개 jar를 거기에 복사하세요. (긴 파일명이 부담스러우면 `javacpp-1.5.13-windows-x86_64.jar` → `javacpp-windows-x86_64.jar`, `ffmpeg-8.0.1-1.5.13-windows-x86_64.jar` → `ffmpeg-windows-x86_64.jar` 식으로 짧게 rename해도 됩니다. 아래 예시는 짧은 이름 기준.)
-   - 그 다음, 공식 런처에서 fabric 프로필 옆 **편집** 또는 **설치 설정** → 화면 아래쪽 **"JVM 인수"** (Java arguments) 칸을 켜고 기존 인수 **끝**에 한 칸 띄우고 다음 한 줄을 추가합니다.
-
-     ⚠ **반드시 절대경로(`C:\Users\...`)로 적어주세요.** 마인크래프트 공식 런처는 JVM 인수의 `%APPDATA%`·`%USERPROFILE%` 같은 환경변수를 풀어주지 않고 글자 그대로 Java 에 넘깁니다. 그러면 boot classpath 가 빈 상태가 되어 영상이 안 나옵니다.
-
-     Windows (사용자명 `홍길동` 예시):
-     ```
-     -Xbootclasspath/a:C:\Users\홍길동\AppData\Roaming\.minecraft\libraries\javacv\javacv.jar;C:\Users\홍길동\AppData\Roaming\.minecraft\libraries\javacv\javacpp.jar;C:\Users\홍길동\AppData\Roaming\.minecraft\libraries\javacv\javacpp-windows-x86_64.jar;C:\Users\홍길동\AppData\Roaming\.minecraft\libraries\javacv\ffmpeg.jar;C:\Users\홍길동\AppData\Roaming\.minecraft\libraries\javacv\ffmpeg-windows-x86_64.jar
-     ```
-     (`C:\Users\<본인 윈도우 사용자명>\AppData\Roaming\` 부분을 본인 사용자 폴더로 바꾸세요. 윈도우키+R → `cmd` → `echo %APPDATA%` 로 정확한 경로 확인 가능.)
-
-     macOS (Apple Silicon 예시):
-     ```
-     -Xbootclasspath/a:/Users/사용자이름/Library/Application Support/minecraft/libraries/javacv/javacv.jar:/Users/사용자이름/Library/Application Support/minecraft/libraries/javacv/javacpp.jar:/Users/사용자이름/Library/Application Support/minecraft/libraries/javacv/javacpp-macosx-arm64.jar:/Users/사용자이름/Library/Application Support/minecraft/libraries/javacv/ffmpeg.jar:/Users/사용자이름/Library/Application Support/minecraft/libraries/javacv/ffmpeg-macosx-arm64.jar
-     ```
-
-     Linux:
-     ```
-     -Xbootclasspath/a:/home/사용자이름/.minecraft/libraries/javacv/javacv.jar:/home/사용자이름/.minecraft/libraries/javacv/javacpp.jar:/home/사용자이름/.minecraft/libraries/javacv/javacpp-linux-x86_64.jar:/home/사용자이름/.minecraft/libraries/javacv/ffmpeg.jar:/home/사용자이름/.minecraft/libraries/javacv/ffmpeg-linux-x86_64.jar
-     ```
-
-     주의:
-     - Windows는 jar 사이를 **세미콜론(`;`)** 으로 구분합니다.
-     - macOS/Linux는 **콜론(`:`)** 으로 구분합니다.
-     - 경로에 띄어쓰기가 있으면(특히 macOS의 `Application Support`) 전체 인수를 큰따옴표로 감싸세요.
-     - `사용자이름` 부분은 실제 자신의 사용자 폴더 이름으로 바꾸세요.
-     - `javacpp-...` 와 `ffmpeg-...` 부분의 jar 이름은 OS에 맞춰 1번에서 고른 그 파일명 그대로 적습니다 (zip 안에는 `javacpp-1.5.13-windows-x86_64.jar`, `ffmpeg-8.0.1-1.5.13-windows-x86_64.jar` 같은 긴 이름으로 들어 있고, 위 예시는 짧게 rename한 것 기준입니다).
-     - **5개 모두** 적어야 합니다. `javacpp-<os>.jar` (네이티브) 가 빠지면 JNI bridge 가 로딩 안 돼서 영상이 검게만 보입니다.
-
-3. 저장 후 **플레이** 를 누르면 영상이 재생됩니다.
-
-> 절차가 너무 번거롭다고 느끼면 **5-A 의 Prism Launcher** 를 권장합니다. 동일한 jar 를 클릭으로 끌어다 놓기만 하면 끝납니다.
-
-### STEP 6. 잘 설치됐는지 확인
 
 게임 안에서 채팅창에 `/videostick` 을 입력하세요. 정상이라면:
 
 - 인벤토리에 **비디오 스틱** 아이템이 들어옵니다 (보라/검정 missing-texture 가 아니라 작대기 모양 아이콘).
-- 보라/검정 missing texture 가 나오면 **STEP 4** 에서 이전 버전 jar(`video_player-0.4.0.jar` / `0.4.1.jar` 등)가 mods 폴더에 같이 남아있는 경우입니다. 다 지우고 `0.4.7` 만 남기고 다시 시작하세요. (0.4.1 이하는 Fabric 26.1.2 model 로더가 unprefixed `item/generated` parent 를 거부해서 스틱 아이콘이 missing-model 큐브로 보입니다 — 0.4.2 에서 수정됨.)
+- 보라/검정 missing texture 가 나오면 **STEP 4** 에서 이전 버전 jar(`video_player-0.4.0.jar` / `0.4.1.jar` 등)가 mods 폴더에 같이 남아있는 경우입니다. 다 지우고 `0.4.11` 만 남기고 다시 시작하세요. (0.4.1 이하는 Fabric 26.1.2 model 로더가 unprefixed `item/generated` parent 를 거부해서 스틱 아이콘이 missing-model 큐브로 보입니다 — 0.4.2 에서 수정됨.)
 
 ---
 
@@ -229,18 +161,27 @@ Fabric은 마인크래프트에 모드 기능을 추가해 주는 로더입니
 
 ## 알려진 이슈
 
-- JavaCV가 안 잡혀있으면 영상 자리만 잡힐 뿐 검게 보입니다. 로그 파일(`.minecraft/logs/latest.log`)에서 `JavaCV not on classpath` WARN 또는 `JavaCV decode error: ...UnsatisfiedLinkError... jnijavacpp` 메시지로 확인 가능합니다. 후자는 `javacpp-<os>.jar` 네이티브 jar 가 빠진 케이스입니다 (STEP 5-B 1번의 5개 jar 모두 등록되어야 함).
+- 영상 자리만 잡히고 검게 보이는 경우: 자신의 OS·CPU 와 다른 플랫폼의 jar 를 받았거나, 이전 버전(0.4.7 이하)의 `-Xbootclasspath/a:...javacv...` JVM 인수가 그대로 남아 있는 경우가 가장 흔합니다. 로그 파일(`.minecraft/logs/latest.log`)에서 `JavaCV not on classpath` WARN 또는 `UnsatisfiedLinkError... jnijavacpp` 메시지로 확인 가능합니다.
 - 0.3.x 이하 버전에서 만든 영상은 새 버전(0.4.x) 에서 보이지 않으니 다시 배치해야 합니다.
 
 ---
 
 ## 개발자용 빌드
 
+바닐라(JavaCV 미포함, 별도 설치 가정) 빌드:
 ```sh
 JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew build
 ```
+산출물: `build/libs/video_player-0.4.11.jar` (~85KB)
 
-산출물: `build/libs/video_player-0.4.7.jar`
+플랫폼별 fat jar (JavaCV 1.5.13 + ffmpeg 8.0.1 네이티브 nested):
+```sh
+JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew clean build -Pplatform=windows-x86_64
+JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew clean build -Pplatform=linux-x86_64
+JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew clean build -Pplatform=macosx-x86_64
+JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew clean build -Pplatform=macosx-arm64
+```
+산출물: `build/libs/video_player-<platform>-0.4.11.jar` (~21-32MB, jar 내부에 nested 로 javacv/javacpp/ffmpeg jar 5개 포함, Fabric loader 가 런타임에 classpath 로 풀어서 로딩)
 
 JavaCV를 직접 의존성으로 가져오는 경우의 Maven 좌표:
 ```

build.gradle

@@ -7,8 +7,25 @@ plugins {
 version = project.mod_version
 group = project.maven_group
 
+// Optional platform bundle target: `-Pplatform=windows-x86_64` etc. produces a fat jar
+// with that platform's JavaCV + FFmpeg natives nested inside via Fabric's `include`
+// directive. Without `-Pplatform`, the build matches pre-0.4.8 behavior (small jar,
+// user supplies JavaCV separately).
+def javacvPlatform = (project.findProperty('platform') ?: '').toString()
+def bundleJavaCv = !javacvPlatform.isEmpty()
+
+def javacvVersion = '1.5.13'
+def ffmpegVersion = '8.0.1-1.5.13'
+def supportedPlatforms = ['windows-x86_64', 'linux-x86_64', 'macosx-x86_64', 'macosx-arm64']
+if (bundleJavaCv && !supportedPlatforms.contains(javacvPlatform)) {
+    throw new GradleException(
+        "Unknown -Pplatform=${javacvPlatform}. Allowed: ${supportedPlatforms.join(', ')}")
+}
+
 base {
-    archivesName = project.archives_base_name
+    archivesName = bundleJavaCv
+        ? "${project.archives_base_name}-${javacvPlatform}"
+        : project.archives_base_name
 }
 
 repositories {
@@ -26,6 +43,19 @@ dependencies {
 
     implementation "net.fabricmc:fabric-loader:${project.loader_version}"
     implementation "net.fabricmc.fabric-api:fabric-api:${project.fabric_version}"
+
+    if (bundleJavaCv) {
+        // Nest the same 5 jars that the README's manual install step used to require, so
+        // users no longer need -Xbootclasspath/a. `include` adds them as jar-in-jar entries;
+        // Fabric loader unpacks and classloads them at runtime.
+        // `transitive = false` keeps us from dragging in opencv/openblas/etc — we only use
+        // FFmpegFrameGrabber / Frame / Java2DFrameConverter.
+        include(implementation("org.bytedeco:javacv:${javacvVersion}") { transitive = false })
+        include(implementation("org.bytedeco:javacpp:${javacvVersion}") { transitive = false })
+        include(implementation("org.bytedeco:ffmpeg:${ffmpegVersion}") { transitive = false })
+        include(implementation("org.bytedeco:javacpp:${javacvVersion}:${javacvPlatform}") { transitive = false })
+        include(implementation("org.bytedeco:ffmpeg:${ffmpegVersion}:${javacvPlatform}") { transitive = false })
+    }
 }
 
 processResources {

gradle.properties

@@ -5,7 +5,7 @@ org.gradle.configuration-cache=false
 
 # Mod
 mod_id=video_player
-mod_version=0.4.7
+mod_version=0.4.11
 maven_group=com.ejclaw.videoplayer
 archives_base_name=video_player
 

src/main/java/com/ejclaw/videoplayer/client/playback/JavaCvBackend.java

@@ -4,6 +4,8 @@ import com.ejclaw.videoplayer.VideoPlayerMod;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
 
+import org.lwjgl.system.MemoryUtil;
+
 import javax.sound.sampled.AudioFormat;
 import javax.sound.sampled.AudioSystem;
 import javax.sound.sampled.SourceDataLine;
@@ -13,7 +15,7 @@ import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.ShortBuffer;
 import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * SPEC §5.3 — fallback mp4/http(s) backend driven by JavaCV's FFmpegFrameGrabber.
@@ -29,15 +31,45 @@ import java.util.concurrent.atomic.AtomicReference;
 public class JavaCvBackend implements VideoBackend {
     private static final String GRABBER_CLASS = "org.bytedeco.javacv.FFmpegFrameGrabber";
     private static final String FRAME_CLASS   = "org.bytedeco.javacv.Frame";
-    private static final String CONVERTER_CLASS = "org.bytedeco.javacv.Java2DFrameConverter";
     /** {@code AV_SAMPLE_FMT_S16} from {@code org.bytedeco.ffmpeg.global.avutil}. */
     private static final int AV_SAMPLE_FMT_S16 = 1;
+    /** {@code AV_PIX_FMT_RGBA} from {@code org.bytedeco.ffmpeg.global.avutil}. */
+    private static final int AV_PIX_FMT_RGBA = 26;
 
     private final Object lock = new Object();
     private Thread worker;
     private final AtomicBoolean running = new AtomicBoolean(false);
     private final AtomicBoolean paused  = new AtomicBoolean(false);
-    private final AtomicReference<ByteBuffer> latest = new AtomicReference<>();
+    /**
+     * Ring buffer of preallocated RGBA staging slots. Decoder thread writes to {@code ringTail}
+     * under {@link #frameLock}; render thread drains the oldest slot via
+     * {@link #consumeFrame(long, long)} under the same lock.
+     *
+     * <p>0.4.10 used a single staging slot and relied on {@link SourceDataLine#write}
+     * backpressure to pace the decoder. That paced only at audio-buffer granularity (~0.5 s):
+     * the decoder burst-produced ~12 video frames into the slot while the audio line drained,
+     * the consumer (60+ Hz polling) saw only the last frame of each burst, then the decoder
+     * stalled until audio drained again — net effect ~2 fps of visible video despite the
+     * decoder producing at the source's 24 fps. The ring absorbs the burst; combined with the
+     * smaller audio buffer (~0.1 s) below the burst collapses to 2–3 frames which fits in
+     * {@link #FRAME_RING_SLOTS}.
+     *
+     * <p>If the ring still fills, the decoder overwrites the oldest slot and increments
+     * {@link #droppedFrames}. Memory cost: {@code 4 × w × h × 4} bytes (32 MB at 1080p,
+     * ~130 MB at 4K).
+     */
+    private static final int FRAME_RING_SLOTS = 4;
+    private final Object frameLock = new Object();
+    private final ByteBuffer[] ringBufs = new ByteBuffer[FRAME_RING_SLOTS];
+    private final int[] ringBytes = new int[FRAME_RING_SLOTS];
+    private int ringHead = 0;  // next slot to consume
+    private int ringTail = 0;  // next slot to produce into
+    private int ringCount = 0;
+
+    /** Decoder telemetry (cumulative). Logged ~every 10 s from the decode thread. */
+    private final AtomicLong producedFrames = new AtomicLong();
+    private final AtomicLong consumedFrames = new AtomicLong();
+    private final AtomicLong droppedFrames  = new AtomicLong();
     private volatile int width = 0;
     private volatile int height = 0;
     private volatile float gain = 1.0F;
@@ -87,14 +119,39 @@ public class JavaCvBackend implements VideoBackend {
     public int videoHeight() { return height; }
 
     @Override
-    public ByteBuffer pollFrame() {
+    public boolean consumeFrame(long dstAddr, long maxBytes) {
-        return latest.getAndSet(null);
+        synchronized (frameLock) {
+            if (ringCount <= 0) return false;
+            int idx = ringHead;
+            int n = ringBytes[idx];
+            ByteBuffer buf = ringBufs[idx];
+            // Always advance head regardless of memcpy outcome — otherwise a single oversize
+            // frame (e.g. mid-resize) would jam the ring forever.
+            ringHead = (idx + 1) % FRAME_RING_SLOTS;
+            ringCount--;
+            if (buf == null || n <= 0 || n > maxBytes) {
+                // Texture not yet sized for this frame, or empty slot — skip. ensureTexture()
+                // runs in Entry.tryUpload() before consumeFrame, so n > maxBytes only happens
+                // on the exact tick of a resolution change.
+                return false;
+            }
+            MemoryUtil.memCopy(MemoryUtil.memAddress(buf), dstAddr, n);
+            consumedFrames.incrementAndGet();
+            return true;
+        }
     }
 
     @Override
     public void close() {
         closed = true;
         stopWorker();
+        synchronized (frameLock) {
+            for (int i = 0; i < FRAME_RING_SLOTS; i++) {
+                ringBufs[i] = null;
+                ringBytes[i] = 0;
+            }
+            ringHead = ringTail = ringCount = 0;
+        }
     }
 
     private void stopWorker() {
@@ -137,6 +194,7 @@ public class JavaCvBackend implements VideoBackend {
             Method getAudioChannels = grabberCls.getMethod("getAudioChannels");
             Method setOpt = grabberCls.getMethod("setOption", String.class, String.class);
             Method setSampleFormat  = grabberCls.getMethod("setSampleFormat", int.class);
+            Method setPixelFormat   = grabberCls.getMethod("setPixelFormat", int.class);
 
             // HTTP(S) tuning for streaming URLs (webm via Range / chunked transfer).
             // Lower timeouts → close() snaps shut fast when an anchor is deleted mid-stream;
@@ -157,6 +215,16 @@ public class JavaCvBackend implements VideoBackend {
                 "video_player/" + com.ejclaw.videoplayer.VideoPlayerMod.MOD_ID); } catch (Throwable ignored) {}
             // Force interleaved signed 16-bit PCM so the audio sink path is single-shape.
             try { setSampleFormat.invoke(grabber, AV_SAMPLE_FMT_S16); } catch (Throwable ignored) {}
+            // Force RGBA output so frame.image[0] is a ByteBuffer we can memcpy straight into
+            // the GPU texture. Without this, frame.image[0] is BGR24 and we'd have to round-trip
+            // through Java2DFrameConverter → BufferedImage.getRGB() → per-pixel ARGB→RGBA loop,
+            // which spends 20-50ms of Java work per 1080p frame and was the dominant stutter
+            // source in 0.4.7/0.4.8: when the decoder fell behind real time, the audio buffer
+            // drained, backpressure vanished, and the decoder burst-fired catch-up frames into
+            // the single-slot AtomicReference (dropping all but the last) before the buffer
+            // refilled and blocked it again. swscale's native SIMD does the same conversion in
+            // <1ms per frame, so the decoder consistently keeps real-time pace.
+            try { setPixelFormat.invoke(grabber, AV_PIX_FMT_RGBA); } catch (Throwable ignored) {}
 
             start.invoke(grabber);
             this.width  = (int) getW.invoke(grabber);
@@ -168,12 +236,32 @@ public class JavaCvBackend implements VideoBackend {
             localAudioLine = openLine(sampleRate, audioChannels);
             this.audioLine = localAudioLine;
 
+            // Decoder spec — printed once per playback so the user log shows what the decoder
+            // actually sees (resolution / frame rate / sample rate). Used to verify our pacing
+            // assumptions (e.g. ring depth, audio buffer length) match the source.
+            double srcFrameRate = 0;
+            try { srcFrameRate = ((Number) grabberCls.getMethod("getFrameRate").invoke(grabber)).doubleValue(); }
+            catch (Throwable ignored) {}
+            VideoPlayerMod.LOG.info(
+                "[{}] decoder started: {}x{} @ {} fps, audio {} Hz x{}, ring={} slots",
+                VideoPlayerMod.MOD_ID, width, height,
+                String.format("%.2f", srcFrameRate),
+                sampleRate, audioChannels, FRAME_RING_SLOTS);
+
             Class<?> frameCls    = Class.forName(FRAME_CLASS);
             Field imageField     = frameCls.getField("image");
             Field samplesField   = frameCls.getField("samples");
-            Class<?> convCls     = Class.forName(CONVERTER_CLASS);
+            // Java2DFrameConverter is no longer used now that we read RGBA bytes directly,
-            Object converter     = convCls.getDeclaredConstructor().newInstance();
+            // but we still resolve its class so a future code path could fall back to it if a
-            Method toImage       = convCls.getMethod("getBufferedImage", frameCls);
+            // grabber refuses setPixelFormat. Keep the lookup defensive.
+
+            // Stats sampling: every 10 s of wall-clock we log produced/consumed/dropped deltas
+            // and the implied fps. Lets us tell from the log whether the decoder is keeping
+            // real-time pace (produced≈source fps) and whether the ring is overflowing
+            // (dropped>0). All counters are cumulative; we keep the previous sample to compute
+            // deltas.
+            long statsLastNs = System.nanoTime();
+            long lastProd = 0, lastCons = 0, lastDrop = 0;
 
             while (running.get() && !closed) {
                 if (paused.get()) { Thread.sleep(20); continue; }
@@ -200,15 +288,65 @@ public class JavaCvBackend implements VideoBackend {
                 }
 
                 Object[] images = (Object[]) imageField.get(frame);
-                if (images != null && images.length > 0) {
+                if (images != null && images.length > 0 && images[0] instanceof ByteBuffer src) {
-                    java.awt.image.BufferedImage img =
+                    // frame.image[0] is the swscale-converted RGBA plane, reused by the grabber
-                        (java.awt.image.BufferedImage) toImage.invoke(converter, frame);
+                    // across grab() calls. Copy into the next ring slot under frameLock so the
-                    if (img != null) {
+                    // render thread's consumeFrame() sees coherent frames in FIFO order.
-                        ByteBuffer buf = toRgba(img);
+                    //
-                        if (buf != null) latest.set(buf);
+                    // Allocation is one-time per slot, lazily on first use (or on a resolution
+                    // upgrade) — never per frame. 0.4.9's per-frame allocateDirect was the
+                    // primary memory-churn problem; 0.4.10 fixed that; 0.4.11 adds the ring on
+                    // top to absorb the burst-then-stall caused by SourceDataLine backpressure
+                    // pacing only at audio-buffer granularity.
+                    int need = src.remaining();
+                    if (need > 0) {
+                        int srcPos = src.position();
+                        long srcAddr = MemoryUtil.memAddress(src) + srcPos;
+                        synchronized (frameLock) {
+                            int idx = ringTail;
+                            if (ringBufs[idx] == null || ringBufs[idx].capacity() < need) {
+                                ringBufs[idx] = ByteBuffer.allocateDirect(need).order(ByteOrder.nativeOrder());
+                            }
+                            long dstAddr = MemoryUtil.memAddress(ringBufs[idx]);
+                            MemoryUtil.memCopy(srcAddr, dstAddr, need);
+                            ringBytes[idx] = need;
+                            ringTail = (idx + 1) % FRAME_RING_SLOTS;
+                            if (ringCount < FRAME_RING_SLOTS) {
+                                ringCount++;
+                            } else {
+                                // Ring was full — we overwrote the oldest frame. Advance head
+                                // to point at the next-oldest so consume order stays FIFO.
+                                ringHead = (ringHead + 1) % FRAME_RING_SLOTS;
+                                droppedFrames.incrementAndGet();
+                            }
+                            producedFrames.incrementAndGet();
+                        }
+                        src.position(srcPos); // restore — JavaCV reads it on subsequent grabs
                     }
                 }
 
+                // Periodic stats — once per ~10 s of wall-clock. Includes ring depth so we can
+                // see whether the consumer is keeping up.
+                long now = System.nanoTime();
+                if (now - statsLastNs > 10_000_000_000L) {
+                    long prod = producedFrames.get();
+                    long cons = consumedFrames.get();
+                    long drop = droppedFrames.get();
+                    double elapsedS = (now - statsLastNs) / 1e9;
+                    int depth;
+                    synchronized (frameLock) { depth = ringCount; }
+                    VideoPlayerMod.LOG.info(
+                        "[{}] decoder stats: produced={} ({} fps), consumed={} ({} fps), dropped={} (+{}) over {}s, ring={}/{}",
+                        VideoPlayerMod.MOD_ID,
+                        prod, String.format("%.1f", (prod - lastProd) / elapsedS),
+                        cons, String.format("%.1f", (cons - lastCons) / elapsedS),
+                        drop, (drop - lastDrop),
+                        String.format("%.1f", elapsedS),
+                        depth, FRAME_RING_SLOTS);
+                    statsLastNs = now;
+                    lastProd = prod; lastCons = cons; lastDrop = drop;
+                }
+
                 // If we have an open audio line, SourceDataLine.write() blocks for backpressure
                 // and provides natural A/V pacing; otherwise tick ~60fps so we don't busy-loop.
                 if (localAudioLine == null) Thread.sleep(15);
@@ -243,10 +381,17 @@ public class JavaCvBackend implements VideoBackend {
         try {
             AudioFormat fmt = new AudioFormat(sampleRate, 16, channels, true, false); // signed 16-bit LE
             SourceDataLine line = AudioSystem.getSourceDataLine(fmt);
-            // ~0.5 s of audio buffered in the driver. Smooths over upstream hiccups without
+            // ~0.1 s of audio buffered in the driver. 0.4.10 used 0.5 s, which let the decoder
-            // delaying close() — stopWorker() calls line.stop() / line.flush() to dump it.
+            // burst ~12 video frames between backpressure stalls — way past the video ring's
+            // capacity and the visible cause of the "2-5 fps" stutter the user saw. With 0.1 s
+            // the audio line refills more often, so the decoder is paced more tightly and
+            // bursts collapse to 2-3 frames (well inside FRAME_RING_SLOTS).
+            //
+            // Floor at frameSizeBytes * 256 keeps the buffer above the typical OS / driver
+            // minimum so we don't get UnsupportedOperationException at line.open() on
+            // exotic sample rates.
             int frameSizeBytes = 2 * channels;
-            int bufferBytes    = Math.max(sampleRate * frameSizeBytes / 2, frameSizeBytes * 1024);
+            int bufferBytes    = Math.max(sampleRate * frameSizeBytes / 10, frameSizeBytes * 256);
             line.open(fmt, bufferBytes);
             line.start();
             return line;
@@ -293,17 +438,4 @@ public class JavaCvBackend implements VideoBackend {
         try { return (int) m.invoke(target); } catch (Throwable t) { return 0; }
     }
 
-    private static ByteBuffer toRgba(java.awt.image.BufferedImage img) {
-        int w = img.getWidth(), h = img.getHeight();
-        int[] argb = img.getRGB(0, 0, w, h, null, 0, w);
-        ByteBuffer buf = ByteBuffer.allocateDirect(w * h * 4).order(ByteOrder.nativeOrder());
-        for (int p : argb) {
-            buf.put((byte) ((p >> 16) & 0xFF)); // R
-            buf.put((byte) ((p >>  8) & 0xFF)); // G
-            buf.put((byte) ( p        & 0xFF)); // B
-            buf.put((byte) ((p >> 24) & 0xFF)); // A
-        }
-        buf.flip();
-        return buf;
-    }
 }

src/main/java/com/ejclaw/videoplayer/client/playback/VideoBackend.java

@@ -3,8 +3,6 @@ package com.ejclaw.videoplayer.client.playback;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
 
-import java.nio.ByteBuffer;
-
 /**
  * SPEC §5.3 — minimal playback backend abstraction. Implementations: WatermediaBackend (preferred,
  * when v2 supports the target MC version) and JavaCvBackend (fallback).
@@ -21,10 +19,19 @@ public interface VideoBackend {
     int videoHeight();
 
     /**
-     * Poll a new decoded RGBA frame if one is ready.
+     * If a new RGBA frame is ready, memcpy it directly into the GPU texture buffer at
-     * @return the frame buffer (capacity = w*h*4) or {@code null} if no new frame is ready.
+     * {@code dstAddr} (must have room for at least {@code w*h*4} bytes) and clear the dirty
+     * flag. Returns {@code true} when a frame was written.
+     *
+     * <p>Replaces the prior {@code pollFrame()} which returned a {@link java.nio.ByteBuffer}.
+     * The old contract forced the decoder to either allocate a fresh direct buffer per frame
+     * (huge memory churn at 1080p — see 0.4.10 changelog) or expose a reused buffer whose
+     * memory the decoder could clobber while the renderer was still reading. Pushing the copy
+     * inside the backend lets the decoder hold a single preallocated buffer under its own
+     * lock and copy out to the GPU pointer in one synchronized block — zero allocation, no
+     * race window.
      */
-    ByteBuffer pollFrame();
+    boolean consumeFrame(long dstAddr, long maxBytes);
 
     void close();
 }

src/main/java/com/ejclaw/videoplayer/client/playback/VideoPlayback.java

@@ -9,9 +9,7 @@ import net.minecraft.client.Minecraft;
 import net.minecraft.client.renderer.texture.DynamicTexture;
 import net.minecraft.core.BlockPos;
 import net.minecraft.resources.Identifier;
-import org.lwjgl.system.MemoryUtil;
 
-import java.nio.ByteBuffer;
 import java.nio.file.Path;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -113,10 +111,8 @@ public final class VideoPlayback {
                 continue;
             }
             if (!e.backend.isReady()) continue;
-            ByteBuffer buf = e.backend.pollFrame();
-            if (buf == null) continue;
             try {
-                e.upload(buf);
+                e.tryUpload();
             } catch (Throwable t) {
                 VideoPlayerMod.LOG.warn("[{}] texture upload failed: {}", VideoPlayerMod.MOD_ID, t.toString());
                 e.close();
@@ -188,32 +184,45 @@ public final class VideoPlayback {
             }
         }
 
-        /** Copy an incoming RGBA byte buffer into the texture, resizing if dimensions changed. */
+        /**
-        void upload(ByteBuffer rgba) {
+         * If the backend has a new RGBA frame, copy it straight into the texture's native
+         * pixel buffer and re-upload to GPU. The backend does the memcpy under its own lock
+         * so we never read a half-written frame. RGBA bytes already match NativeImage's
+         * ABGR-int layout in little-endian byte order (byte 0 = R = low byte of the int).
+         */
+        void tryUpload() {
             int w = backend.videoWidth();
             int h = backend.videoHeight();
             if (w <= 0 || h <= 0) return;
             ensureTexture(w, h, false);
             NativeImage img = texture.getPixels();
             if (img == null) return;
-
+            long maxBytes = (long) w * h * 4L;
-            // RGBA bytes from the backend already match NativeImage's ABGR-int layout when
+            if (backend.consumeFrame(img.getPointer(), maxBytes)) {
-            // viewed as little-endian bytes: byte 0 = R (low byte of ABGR int), byte 1 = G,
+                texture.upload();
-            // byte 2 = B, byte 3 = A. So a flat memcpy works — no per-pixel swap needed.
+            }
-            // This replaces a 2M-iteration Java loop with one native memcpy for 1080p frames,
-            // cutting upload time from ~20ms to <1ms and removing the main stutter source.
-            long bytes = (long) w * h * 4L;
-            MemoryUtil.memCopy(MemoryUtil.memAddress(rgba), img.getPointer(), bytes);
-            texture.upload();
         }
 
         void close() {
             try { backend.close(); } catch (Throwable ignored) {}
+            // Unregister from TextureManager BEFORE closing the texture itself, so any
+            // straggler binding by Identifier looks up "no such texture" instead of a closed
+            // GL handle (which crashes the renderer on the next frame). Renderer pipelines
+            // can cache RenderType objects keyed by Identifier across frames, and on delete
+            // the old anchor's frame can still be in flight in the submit buffer when its
+            // texture closes — without this release(), the bind would dereference a freed
+            // GL handle.
+            if (registered) {
+                Minecraft mc = Minecraft.getInstance();
+                if (mc != null) {
+                    try { mc.getTextureManager().release(id); } catch (Throwable ignored) {}
+                }
+                registered = false;
+            }
             if (texture != null) {
                 try { texture.close(); } catch (Throwable ignored) {}
                 texture = null;
             }
-            // texture manager keeps the registration; the texture itself is closed.
         }
     }
 }

src/main/java/com/ejclaw/videoplayer/client/playback/WatermediaBackend.java

@@ -4,8 +4,6 @@ import com.ejclaw.videoplayer.VideoPlayerMod;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
 
-import java.nio.ByteBuffer;
-
 /**
  * SPEC §5.3 / §5.4 — WaterMedia v2 backend. Reflection-only so the mod jar stays clean of
  * compile-time WaterMedia dependencies. Until a v2 build supports 1.21.6+ this returns
@@ -38,8 +36,8 @@ public class WatermediaBackend implements VideoBackend {
     @Override public int videoHeight() { return height; }
 
     @Override
-    public ByteBuffer pollFrame() {
+    public boolean consumeFrame(long dstAddr, long maxBytes) {
-        return null; // no frames until v2 is wired up
+        return false; // no frames until v2 is wired up
     }
 
     @Override