feat: replace Decord with video_reader-rs (#5163)

Signed-off-by: Xinyuan Tong <justinning0323@outlook.com>
Co-authored-by: Xinyuan Tong <justinning0323@outlook.com>

python/sglang/srt/multimodal/processors/base_processor.py

@@ -206,7 +206,7 @@ class BaseMultimodalProcessor(ABC):
         estimate the total frame count from all visual input
         """
         # Lazy import because decord is not available on some arm platforms.
-        from decord import VideoReader, cpu
+        from video_reader import PyVideoReader, cpu
 
         # Before processing inputs
         if not image_data or len(image_data) == 0:
@@ -216,7 +216,7 @@ class BaseMultimodalProcessor(ABC):
             if isinstance(image, str) and image.startswith("video:"):
                 path = image[len("video:") :]
                 # Estimate frames for the video
-                vr = VideoReader(path, ctx=cpu(0))
+                vr = PyVideoReader(path, threads=0)
                 num_frames = len(vr)
             else:
                 # For images, each contributes one frame