[mpeg2-dev] general doubt about PES packetization.

[anand m. <kvm...@gm...>]

Hi Keith,
              I have a doubt with PES packetization. According to what i
learnt PES packets carry elementary stream data , either video or audio but
not both. I also read that if the PES packet carries video elementary stream
then it carries the contiguous bits from the elementary stream.

               I want to clarify one point, will a PES packet carry only one
coded picture, say an I or a B or a P? or a particular PES packet can have
last slice of a picture ending and then followed immediately by the next
picutre header?? I am working on a small project where
I wrote a small wrapper over the libmpeg2 mpeg2dec.c to *get the whole bytes
* of a coded picture(included with the PES headers and transport stream
headers),The video packets are from a transport stream. i wanted to clarify
the way i do it,  i do it as follows.....

i modify the prototype of decode_mpeg2 of mpeg2dec.c as follows *decode_mpeg2
(uint8_t *start , unit8_t *end, uint8_t *buffer) * where the buffer refers
to the 188 byte packet(video packet) of a transport stream which is passed
explicitly by me. The buffer should contain all the headers of the transport
stream and then followed by the PES headers.
Now in decide_mpeg2 function
 in case STATE_PICTURE : when the picture header and picture coding
extension are recognized, i assume that a new picture has been identified
and then i start pushing the buffers (the 188 byte packets )into a data
structure till i again hit STATE_SLICE state.

so when i encounter STATE_SLICE , my logic assumes that the data structure
has all the data of that particular picture along with the PES headers and
transport stream headers.

I know the logic will work only if a new picture definition will not start
in middle of a PES packet that is right after the last picture has been
identified. It would be really helpful if you can let me know if i am doing
something wrong. I can explain if some point was not clear.


thanks & regards
Anand Meher