From 6f97cfa72da2f9d781e82fc3b8f09c7b3cd41b6c Mon Sep 17 00:00:00 2001
From: Odilon Hugonnot <odilon.hugonnot@gmail.com>
Date: Fri, 29 May 2026 14:59:24 +0000
Subject: [PATCH] fix(transcode): only pick a GPU encoder when its device is
 actually present
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detect_hw_encoder() in 'auto' mode picked nvenc as soon as ffmpeg *listed*
h264_nvenc — even on a host with no NVIDIA GPU. The encoder is compiled into many
ffmpeg builds, so on a GPU-less server transcoding failed at runtime with
"[h264_nvenc] Cannot load libcuda.so.1 / Error initializing output stream", and
the player showed "invalid video source". Observed in production (no GPU, ffmpeg
shipping nvenc).

Now nvenc requires a real NVIDIA device (/dev/nvidia0 or /dev/nvidiactl) and
v4l2m2m requires /dev/video10 — mirroring the device check VAAPI already does.
'auto' falls back to software (libx264) when no usable device exists. Explicit
FFMPEG_HW_ACCEL still forces a backend for non-standard setups.

Added HwAccelTest::testGpuBackendChosenOnlyWhenDevicePresent locking the invariant.
phpunit 442/887 green, PHPStan clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 functions.php         | 13 +++++++++----
 tests/HwAccelTest.php | 21 +++++++++++++++++++++
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/functions.php b/functions.php
index 78ce07c..c534278 100644
--- a/functions.php
+++ b/functions.php
@@ -743,15 +743,20 @@ function detect_hw_encoder(): string {
         }
     }
 
-    // NVENC (Nvidia GPU)
+    // NVENC (Nvidia GPU) — h264_nvenc peut être compilé dans ffmpeg SANS qu'aucun
+    // GPU ne soit présent. Exiger un device NVIDIA réel, sinon on choisirait nvenc
+    // sur une machine sans carte → échec runtime "Cannot load libcuda.so.1" et
+    // lecture cassée. (VAAPI fait déjà cette vérif de device plus haut.)
     $encoders = shell_exec('ffmpeg -encoders 2>/dev/null') ?? '';
-    if (str_contains($encoders, 'h264_nvenc')) {
+    $hasNvidiaDevice = file_exists('/dev/nvidia0') || file_exists('/dev/nvidiactl');
+    if ($hasNvidiaDevice && str_contains($encoders, 'h264_nvenc')) {
         $cached = 'nvenc';
         return $cached;
     }
 
-    // V4L2 M2M (Raspberry Pi 4)
-    if (file_exists('/dev/video10') || str_contains($encoders, 'h264_v4l2m2m')) {
+    // V4L2 M2M (Raspberry Pi 4) — pareil : exiger le device ET l'encodeur, pas l'un
+    // ou l'autre (un ffmpeg complet liste h264_v4l2m2m même hors Pi).
+    if (file_exists('/dev/video10') && str_contains($encoders, 'h264_v4l2m2m')) {
         $cached = 'v4l2m2m';
         return $cached;
     }
diff --git a/tests/HwAccelTest.php b/tests/HwAccelTest.php
index 4416445..704a062 100644
--- a/tests/HwAccelTest.php
+++ b/tests/HwAccelTest.php
@@ -28,6 +28,27 @@ public function testDetectHwEncoderReturnsNoneWhenNoGpu(): void
         $this->assertNotEmpty($result);
     }
 
+    /**
+     * En mode auto, un backend GPU ne doit être choisi QUE si son device existe —
+     * sinon ffmpeg liste l'encodeur (compilé) mais l'encodage plante au runtime
+     * (ex. nvenc sans GPU : "Cannot load libcuda.so.1"). Régression réelle observée
+     * en prod sur un serveur sans carte dont le ffmpeg embarquait nvenc.
+     */
+    public function testGpuBackendChosenOnlyWhenDevicePresent(): void
+    {
+        $result = detect_hw_encoder();
+        if ($result === 'nvenc') {
+            $this->assertTrue(
+                file_exists('/dev/nvidia0') || file_exists('/dev/nvidiactl'),
+                'nvenc ne doit être choisi que si un device NVIDIA est présent'
+            );
+        } elseif ($result === 'v4l2m2m') {
+            $this->assertTrue(file_exists('/dev/video10'), 'v4l2m2m exige /dev/video10');
+        } else {
+            $this->assertContains($result, ['none', 'vaapi']);
+        }
+    }
+
     // ── buildFfmpegCodecArgs with hardware encoders ──────────────────────
 
     public function testBuildFfmpegCodecArgsSoftware(): void