refactor: Streaming MP4 files in the browser using video html element instead of waiting for the entire file to download before playing

Author: kevin.zhang

app/controllers/v1/video.py

@@ -3,7 +3,7 @@
 import shutil
 
 from fastapi import Request, Depends, Path, BackgroundTasks, UploadFile
-from fastapi.responses import FileResponse
+from fastapi.responses import FileResponse, StreamingResponse
 from fastapi.params import File
 from loguru import logger
 
@@ -137,7 +137,37 @@ def upload_bgm_file(request: Request, file: UploadFile = File(...)):
 async def stream_video(request: Request, file_path: str):
     tasks_dir = utils.task_dir()
     video_path = os.path.join(tasks_dir, file_path)
-    if os.path.isfile(video_path):
-        return FileResponse(video_path, media_type="video/mp4", filename=file_path)
-    else:
-        return {"message": "File not found."}
+    range_header = request.headers.get('Range')
+    video_size = os.path.getsize(video_path)
+    start, end = 0, video_size - 1
+
+    length = video_size
+    if range_header:
+        range_ = range_header.split('bytes=')[1]
+        start, end = [int(part) if part else None for part in range_.split('-')]
+        if start is None:
+            start = video_size - end
+            end = video_size - 1
+        if end is None:
+            end = video_size - 1
+        length = end - start + 1
+
+    def file_iterator(file_path, offset=0, bytes_to_read=None):
+        with open(file_path, 'rb') as f:
+            f.seek(offset, os.SEEK_SET)
+            remaining = bytes_to_read or video_size
+            while remaining > 0:
+                bytes_to_read = min(4096, remaining)
+                data = f.read(bytes_to_read)
+                if not data:
+                    break
+                remaining -= len(data)
+                yield data
+
+    response = StreamingResponse(file_iterator(video_path, start, length), media_type='video/mp4')
+    response.headers['Content-Range'] = f'bytes {start}-{end}/{video_size}'
+    response.headers['Accept-Ranges'] = 'bytes'
+    response.headers['Content-Length'] = str(length)
+    response.status_code = 206  # Partial Content
+
+    return response