使用DataInputStream读取小字节长度时读取性能降低

Question

Currently I'm writing a video stream receiver on Java TCP Socket. I have managed to display the stream just fine but I'm concerned on the performance of my socket reading as I need to reduce the latency.

The first 8 bytes of each video payload representing the length of the video payload itself. So I have to get the length of the video payload first, and then read the video payload until the specified length has been reached before I pass it to the decoder. The code is something like this:

boolean isRunning = true;
boolean isReadingHeader = true;
byte[] headerBuff = new byte[8];
byte[] videoBuff;  
Socket socket;
/* socket setup goes here */
DataInputStream dis = new DataInputStream(socket.getInputStream());
while(isRunning)
{
    if(isReadingHeader) /* reading the header to get the length */
    {
        long start = System.currentTimeMillis();
        dis.readFully(headerBuff);
        long end = System.currentTimeMillis() - start;
        System.out.println("Read Header : " + end + " ms");
        int len = ....
        videoBuff = new byte[len];
        isReadingHeader = false;
    }
    else  /* reading the video payload*/
    {
        long start = System.currentTimeMillis();
        dis.readFully(videoBuff);
        long end = System.currentTimeMillis() - start;
        System.out.println("Read Payload: " + end + " ms");
        /* Passing to Decoder goes here */
        isReadingHeader = true;
    } 
}

Since the outputs are endless, I put the first 20 outputs as below (the outputs after that are consistant):

Read Header : 6 ms
Read Payload : 0 ms
Read Header : 0 ms
Read Payload : 0 ms
Read Header : 0 ms
Read Payload : 0 ms
Read Header : 200 ms
Read Payload : 1 ms
Read Header : 142 ms
Read Payload : 0 ms
Read Header : 138 ms
Read Payload : 0 ms
Read Header : 135 ms
Read Payload : 0 ms
Read Header : 146 ms
Read Payload : 0 ms
Read Header : 136 ms
Read Payload : 0 ms
Read Header : 147 ms
Read Payload : 0 ms

As you can see, reading 8 bytes into headerBuff is taking between 100ms to 200ms while reading the video payload which its length can be 30k++ is done in 0 ms. I'm wondering why its taking too long to read 8 bytes of data. I have tried readByte() in for loop and also the read() methods but the execution time is just the same. FYI, i tested this on localhost and this latency issue is not happening on my .NET stream receiver (means network is not the reason).

Thanks!

Answer 1

Instead of

DataInputStream dis = new DataInputStream(socket.getInputStream());

Try using BufferedInputStream

DataInputStream dis = new DataInputStream(new BufferedInputStream(socket.getInputStream()));

hope it helps