avcodec: reduce the default maximum number threads

Close #19490

modules/codec/avcodec/video.c

@@ -556,7 +556,7 @@ int InitVideoDec( vlc_object_t *obj )
             i_thread_count++;
 
         //FIXME: take in count the decoding time
-        i_thread_count = __MIN( i_thread_count, p_codec->id == AV_CODEC_ID_HEVC ? 12 : 6 );
+        i_thread_count = __MIN( i_thread_count, p_codec->id == AV_CODEC_ID_HEVC ? 10 : 6 );
     }
     i_thread_count = __MIN( i_thread_count, p_codec->id == AV_CODEC_ID_HEVC ? 32 : 16 );
     msg_Dbg( p_dec, "allowing %d thread(s) for decoding", i_thread_count );