lowercase stream names

Author: Lukas Wingerberg

server/grpc-ffmpeg.py

@@ -83,10 +83,10 @@ async def read_stream(stream, response_type, stream_name):
                 logger.info(f'{stream_name}: {line.decode("utf-8").strip()}')
                 yield response_type(output=line.decode('utf-8'), stream=stream_name)
 
-        async for response in read_stream(process.stdout, ffmpeg_pb2.CommandResponse, "STDOUT"):
+        async for response in read_stream(process.stdout, ffmpeg_pb2.CommandResponse, "stdout"):
             yield response
 
-        async for response in read_stream(process.stderr, ffmpeg_pb2.CommandResponse, "STDERR"):
+        async for response in read_stream(process.stderr, ffmpeg_pb2.CommandResponse, "stderr"):
             yield response
 
         await process.wait()