From 2e6518bf4b7092b10599b4cf2a2dcb4b6c23aa9d Mon Sep 17 00:00:00 2001
From: lizerk <lizerk-dev@gmail.com>
Date: Mon, 24 Aug 2026 14:05:03 +0300
Subject: [PATCH] Improve FFmpeg video thumbnail fallback handling

---
 backend/tasks/media.py | 61 +++++++++++++++++++++++++-----------------
 1 file changed, 36 insertions(+), 25 deletions(-)

diff --git a/backend/tasks/media.py b/backend/tasks/media.py
index e917975e..7446c839 100644
--- a/backend/tasks/media.py
+++ b/backend/tasks/media.py
@@ -26,6 +26,8 @@ IMAGE_EXTENSIONS = {
     ".webp",
 }
 VIDEO_EXTENSIONS = {
+    ".3gp",
+    ".avi",
     ".m4v",
     ".mkv",
     ".mov",
@@ -97,19 +99,17 @@ def _render_video_thumbnail(attachment: TaskAttachment) -> bytes:
             output_path = output_file.name
 
         filter_value = "scale=640:280:force_original_aspect_ratio=increase,crop=640:280"
-        command = [
-            ffmpeg,
-            "-hide_banner",
-            "-loglevel",
-            "error",
-            "-ss",
-            "0.5",
-            "-i",
-            input_path,
+        command_prefix = [ffmpeg, "-hide_banner", "-loglevel", "error"]
+        command_suffix = [
+            "-map",
+            "0:v:0",
             "-frames:v",
             "1",
             "-vf",
             filter_value,
+            "-an",
+            "-sn",
+            "-dn",
             "-c:v",
             "libwebp",
             "-quality",
@@ -117,22 +117,33 @@ def _render_video_thumbnail(attachment: TaskAttachment) -> bytes:
             "-y",
             output_path,
         ]
-        result = subprocess.run(
-            command,
-            capture_output=True,
-            check=False,
-            timeout=30,
-        )
-        if result.returncode != 0:
-            command[5] = "0"
-            result = subprocess.run(
-                command,
-                capture_output=True,
-                check=False,
-                timeout=30,
-            )
-        if result.returncode != 0:
-            raise RuntimeError(result.stderr.decode("utf-8", errors="replace"))
+        commands = [
+            # Fast input seek works for ordinary MP4/WebM files.
+            [*command_prefix, "-ss", "0.5", "-i", input_path, *command_suffix],
+            # Accurate output seek handles fragmented MP4/MOV screen recordings
+            # whose first keyframe cannot be reached by input seeking.
+            [*command_prefix, "-i", input_path, "-ss", "0.5", *command_suffix],
+            # Some recordings start on a non-zero timeline. In that case use the
+            # first frame FFmpeg can decode instead of requiring a timestamp.
+            [*command_prefix, "-i", input_path, *command_suffix],
+        ]
+        last_error = "FFmpeg did not produce a video thumbnail."
+        for command in commands:
+            try:
+                result = subprocess.run(
+                    command,
+                    capture_output=True,
+                    check=False,
+                    timeout=30,
+                )
+            except subprocess.TimeoutExpired as error:
+                last_error = str(error)
+                continue
+            if result.returncode == 0 and Path(output_path).stat().st_size > 0:
+                break
+            last_error = result.stderr.decode("utf-8", errors="replace")
+        else:
+            raise RuntimeError(last_error)
         return Path(output_path).read_bytes()
     finally:
         if temporary_input and input_path: