[M4IF Technotes] VBV underflow problems

[arcangelo.bruna st.com]

     Hi.
     I'm implementing a real time Simple Profile encoder.
     I have a problem in the VBV implementation.
     The standard says to use the stuffing bits (bytes) to avoid underflow, 
     but, in this profile, only the stuffing MB are allowable, because the 
     stuffing_start_code can not be used.
     Unfortunately, for a real time implementation, it is not really a 
     simple thing: in fact, they can not introduced in the next frame 
     because it will be inserted in the VB surely when it is already empty.
     So we must insert them only in the already encoded frame, so the frame 
     size become bigger.
     But what happen if the frame size become too bigger so that when the 
     decoder requires it the frame it is not transmitted at all?
     Another problem: we can not re-encode the frame (due to the real time 
     encoding constraints), so we will insert the stuffing MB at the end of 
     the frame. But what happen if, using the Video Packet, the last video 
     packet become bigger than the profile's constraints (2048 bits for the 
     SP   L1)?
     All these problems could be avoided allowing the stuffing_start_code 
     in each profiles & levels. Is there a reason why it is not so? Is 
     possible to suggest it to the standardization committee?
     Thanks,
        Arcangelo.