[Live-devel] presentationTime and B-Frames

[Ross Finlayson]

>  > Note that In your original MPEG-2 stream, with B-frames, the frames
>>  will be in decoding order, which is different from the display order,
>>  and thus different from the order of frames in the resulting MPEG-4
>>  stream (because that doesn't have B frames).  In particular, the
>>  presentation times in the original MPEG-2 stream, with B-frames, will
>>  *not* be monotonically increasing.  You will need to reorder the
>>  presentation times accordingly when you convert the stream to MPEG-4
>>  (without B-frames).
>>  
>
>My source is the vobStreamer application. Examining the packets it looks
>like if they are sent rather in display order (IBBPBBPBBPBBI...).

I believe you're mistaken on this point.  E.g., the first B-frames 
that you receive after each I-frame are  actually intended to be 
displayed *before* the i-frame.  That's why the B-frames will have a 
lower presentation time than the I-frame.

You need to take this into account when assigning presentation times 
to the transcoded MPEG-4 frames (without B-frames).

-- 

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/