[streaming] Re: TS Discontinuities

[Christophe Massiot]

On Tue, Jun 21, 2005, Dermot McGahon wrote:

> I need to understand these a little better,
> 
> libdvbpsi error (PSI decoder): TS discontinuity (received 0, expected 15)
> libdvbpsi error (PSI decoder): TS discontinuity (received 7, expected 6)
> libdvbpsi error (PSI decoder): TS discontinuity (received 9, expected 8)
> libdvbpsi error (PSI decoder): TS discontinuity (received 5, expected 4)
> 
> I'm streaming mpeg-2 ts/udp and on a channel change I get a few  
> discontinuities,
> but more worrying is that during streaming I sometimes get 10-20  
> discontinuities
> with artifacts resulting on screen.
> 
> Questions:
> 
> - It seems libdvbpsi expects CC of 0 when starting playback. What is the

This is fixed in libdvbpsi svn trunk.

>   range of the CC's in the transport stream packets? How often does it

0-15

>   loop back to 0? Is it based on the GOP?

Very often, no relation to the GOP.

> - How should I read the above? VLC received CC 15, 0, 1, 2, 3, 4, 5, 7, 9?

Well except there may have been 1000 correct packets between two lines...

> - UDP packet size is 1316 (7 TS packets). Is this was due to a udp packet
>   being lost wouldn't I see a gap of mod 7 in the discontinuities?

Discontinuities are per-ES. libdvbpsi only prints the discontinuities
occurring in the PSIs (PAT and PMT), VLC reports the discontinuities on
all ESes if you pass -vvv. So you may have lost 6 video TS, but only 1
PAT packet, resulting in those TS discontinuities messages of only 1
unit.

> - Does UDP packet reordering come into play here?

Probably not.

-- 
Christophe Massiot.

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