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

Robert Scheffler Bob at pricom.com
Sun Mar 19 01:59:09 CET 2006

After some off-line discussion, and a bit of research, I think this
accurately describes the need and my problem.

(Many thanks to Måns Rullgård for his time in helping me describe this

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. This
alignment requirement is dictated in the USA CableLabs VOD Content Encoding
Profiles, and is used in all US Cable System VOD deployment. So it isn’t
just my weird situation. I would think this should be useful to others as

The error I am having means that the ingest analyzer on the server receiving
device has not detected a picture header within two transport packets of
PUSI being set for the video PID (counting only video PID packets). There
are circumstances when the streaming chip needs to alter the picture header
and extension and its offsets are limited to two packets.

Måns commented:
OK, I think I understand the problem.  IIRC the VLC muxer uses a more
typical approach of ~2k size PES packets with no specific alignment
constraints. Modifying it to produce the type of stream you want shouldn't
be difficult, though.

The question is can anyone modify the VLC muxer to allow this alignment

I would be greatly appreciative of any effort to help me with this
non-standard alignment.

Thanks so much for any input.

Bob Scheffler

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