[vlc-devel] VLC 0.8.6 end of support

Rémi Denis-Courmont rdenis at simphalempin.com
Wed Sep 3 09:34:29 CEST 2008

On Tue, 2 Sep 2008 22:59:48 +0200, "Marian Ďurkovič" <md at bts.sk> wrote:
> Unlike VLC, VLS does *not* reconstruct the PCRs,

That is a VLS bug...

> does not remux TS, it just selects the TS packets for required PIDs
> and sends them out. So the stream from VLS is exactly that MPEG-TS
> which the TV station produces for broadcast (production) quality!
> The same is true for my rtpstream - it takes what it gets from the
> and adds 12 bytes of RTP header to each packet.

...but VLC ignores the RTP timestamp for TS streams anyway. Note that it
should not because that's the only way to estimate the delay jitter

> So apparently, the new RTP module works with only one specific
> of PCR interval, delta between PCRs and PTS and other TS parameters
> as implemented by VLC's TS output muxer. When it gets anything else,
> it breaks.

FOR THE LAST TIME: VLC does not use the RTP timestamp for TS. And fenrir's
last RTP fix clearly did not change this.

> Which are obviously holidays at the universities....

Obvious? my universities were open until quite late into June. Plus, we are
not going to fix our schedule to yours.

>> And you'll go to every VLC user to set the option right, right?
> Better than not having an upgrade path at all...

No. Just as bad. Worse actually, as it makes the new features plain

> Yep - except that elementary streams have their PTSs in RTP, so you can
> basically do anything regarding the timing. I.e. even if you feed packets
> down the chain at completely wrong intervals, PTS will ensure correct
> display. With TS, VLC's synchro depends on precise timing - and if you
> for example deliver packet with PCR at wrong time, synchro will shift
> the reference clock to bogus values.  

And the old "stupid" RTP code did exactly that, feed the packet with
varying delay, hence at the wrong time - due to the overly simplistic
re-ordering algorithm. No better than the current code. Of course, if you
receive packet at regular interval, and at high frequency (as is typical
from a TS stream), the jitter will be averaged quite well, and the synchro
will work around irregularities. In other words, both the old and new RTP
receivers are wrong, and abusing the VLC synchro. Only proper jitter
calculation in VLC 1.0 will fix that.

Rémi Denis-Courmont

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