[Mp4-tech] Help with H.264 start code prefix

[video guy]

Hi Madan, 
Thanks for the reply. That definitely gave some insight.
You mentioned to use a buffer that accumulates the packets from the server and extract the NAL units. 
I am writing the sent data into a file at the reciever side, and giving it as an input to the decoder. 
And, I am not sure about the byte stream structure of the encoded video. Can you please throw some light on that. 
I have been using the JM73 version.
I am very new to this, so will be having a lot of questions and hope to get answers from you. :)
Thanks a bunch.  
aar.
Madan <madank interrasystems.com> wrote:
Hi Buddy !!
     At the decoder end, keep a buffer that accumulates the
packets from the server.  From this buffer extract the NAL
packets.  From the bitstream at the reciving end. 
Use this algo to extract the NAL units
for(;;)
        {
            if next 24 bits are 0x000001
        {
           startCodeFound = true
           break;
        }
            else
            {
                flush 8 bits 
            }
        }// for(;;)
        if(true == startCodeFound)
        {
            //startcode found
            // Flush the start code found
            flush 24 bits 
            //Now navigate up to next start code and put the in between stuff
            // in the nal structure.
           for(;;)
           {
               get next 24 bits & check if it equals to 0x000001
              if(false == (next 24 bits == 000001))
               {
                   // search for pattern 0x000000
                   check if next 24 bits are 0x000000
                   if(false == result)
                   {
                       // copy the byte into the buffer
                       copy one byte to the Nal unit 
                   }
                   else
                   {
                       break;
                   }
               }
               else
               {
                   break;
               }
           }//for(;;)
once u got  the nal , decode it ...
Hope this helps u :-)
video guy wrote:
Hello,
I'm trying to use the start code prefix in H.264 but not sure how to go ahead with it.
Here is my problem,
I want to send the h.264 encoded byte stream (which is stored as test.264 file) from one system to another using a client server program in C, and, simulate a packet loss environment. At the reciever, some random data will be lost. 
But, i'm not able to run the decoder due to the lost data. Is there anyway I could make the decoder work ? I have no idea how to use the start code prefix. 
Any help in this regard would be greatly appreciated. 
Thank you 
aar.
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-- 
Thanx & Regards !! 
from Madan 
Interra Systems India Pvt. Ltd. 
A10, Sec9,NOIDA Ph: 0120-2442273/4 Ext 324 
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