Advanced topics – JVC 4ch Network Encoder VN-E4 User Manual
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(1) When frame rate drops deteriorates due to long network delay time
Ⅵ Causes of Frame Rate Deterioration
During transmission via TCP, VN-E4 sends out the following data by receiving the Ack of TCP. When network delay is long, reception of
Ack will be delayed and sending rate will drop. This therefore leads to a drop in the frame rate.
Ⅵ Countermeasure 1
One of the countermeasures to improve this situation is to increase the TCP window size. Use sendbuffer (API argument for sending data to
VN-E4) to increase the outgoing buffer size of VN-E4. In addition, increase the window scale and incoming buffer size at the client's end as
well. If the OS used by the client is Windows, window scale can be altered by changing the registry. Refer to the Windows manual for
details on operation of Windows registry.
Additionally, the total size that can be increased by the sendbuffer argument of API is up to 1MB. Subsequent client requests to increase the
buffer size will be rejected if the 1 MB size has already been used up by other clients.
Ⅵ Countermeasure 2
This problem can be avoided by receiving via multicast. Multicast uses UDP and Ack does not exist. As such, the sender will be able to
continue sending without being affected by network delays.
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