[vlc-devel] Re: Is there a way to force PES alignment to a TS boundary when Streaming UDP?

Robert Scheffler Bob at pricom.com
Thu Mar 16 01:40:52 CET 2006


The text was copied from the guy that wrote the receiving code. I have to
admit this is not my strong point, which is why I had formulated the
question wrong in the first place. I asked that the developer pose the
question so I could pass it to this fine group.

Ideally, I would like to use a capture card and send MPEG2-TS/UDP/IP to this
device in question that conforms to the rule stated below. All works well
except that at random intervals (5 secs to 30 minutes) the alignment goes
out enough to crash the receiver. The receiver doesn’t give much more than a

I don’t have any way to look at the TS/UDP/IP packets so I really can't tell
what is going on. I was hoping someone here would be better armed to help.
If there are any suggestions or tests I can perform, please let me know.

Thank you so much!

Bob Scheffler

> Sorry about the email tread screw-up, my mistake, I won't do it again!
> The requirement is that every access unit in the video elementary
> stream should be aligned to a PES header. That is the first byte of
> each PES packet payload is the first byte of an access unit. The
> data_alignment_indicator bit should also be set in the PES
> header. This type of alignment corresponds to an alignment_type of
> two in the data_stream_alignment_descriptor.

OK, that's a different type of alignment.  Are you sure this is the
problem?  I've never seen any hardware or software requiring such

Måns Rullgård
mru at inprovide.com

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