Add mode to Codec, display C func in err

Author: WyattBlue

av/codec/codec.pyi

@@ -51,6 +51,8 @@ class Codec:
     def is_encoder(self) -> bool: ...
     @property
     def is_decoder(self) -> bool: ...
+    @property
+    def mode(self) -> Literal["r", "w"]: ...
     descriptor: Descriptor
     @property
     def name(self) -> str: ...

av/codec/codec.pyx

@@ -119,7 +119,7 @@ cdef class Codec:
             raise RuntimeError("%s is both encoder and decoder.")
 
     def __repr__(self):
-        mode = "w" if self.is_encoder else "r"
+        mode = self.mode
         return f"<av.{self.__class__.__name__} {self.name} {mode=}>"
 
     def create(self, kind = None):
@@ -130,6 +130,10 @@ cdef class Codec:
         from .context import CodecContext
         return CodecContext.create(self)
 
+    @property
+    def mode(self):
+        return "w" if self.is_encoder else "r"
+
     @property
     def is_decoder(self):
         return not self.is_encoder

av/codec/context.pyx

@@ -324,7 +324,7 @@ cdef class CodecContext:
         cdef int res
         with nogil:
             res = lib.avcodec_send_frame(self.ptr, frame.ptr if frame is not None else NULL)
-        err_check(res)
+        err_check(res, "avcodec_send_frame()")
 
         packet = self._recv_packet()
         while packet:
@@ -337,7 +337,7 @@ cdef class CodecContext:
         cdef int res
         with nogil:
             res = lib.avcodec_send_packet(self.ptr, packet.ptr if packet is not None else NULL)
-        err_check(res)
+        err_check(res, "avcodec_send_packet()")
 
         out = []
         while True:
@@ -365,7 +365,7 @@ cdef class CodecContext:
 
         if res == -EAGAIN or res == lib.AVERROR_EOF:
             return
-        err_check(res)
+        err_check(res, "avcodec_receive_frame()")
 
         frame = self._transfer_hwframe(frame)
 
@@ -384,7 +384,7 @@ cdef class CodecContext:
             res = lib.avcodec_receive_packet(self.ptr, packet.ptr)
         if res == -EAGAIN or res == lib.AVERROR_EOF:
             return
-        err_check(res)
+        err_check(res, "avcodec_receive_packet()")
 
         if not res:
             return packet