[vlc-devel] VLC 0.8.6 end of support

Marian Ďurkovič md at bts.sk
Tue Sep 2 13:16:39 CEST 2008

On Tue, Sep 02, 2008 at 12:33:27PM +0200, Rémi Denis-Courmont wrote:
> It is perfectly usable to me.

Try any commercial MPEG-TS over RTP source, VLS, or e.g my rtpstream
utility. No sound, log full of "PTS out of range" etc. The new RTP
module doesn't cooperate with clock synchro correctly, and seem
to only work when streaming from VLC to VLC. (BTW, doesn't it accidentially
feed RTP timestamps to the synchro?)
> It adds supports for other codecs (especially µ/A-law), and more transport
> protocols. Things that people have been asking for, for a long time. That
> could not be provided with the previous architecture, which was a
> TS-specific hack. RTP simply is _NOT_ an access (live555 is not an access
> either, is it?). And it is pretty much impossible for both to cohabit.

They could always coexist with some config option - we already have
no-sap-parse for disabling VLC's internal RTP module and sending
everything to live555. I could also imagine handling MPEG-TS by the
previous code and all other RTP elementary streams with the new code
- after all, MPEG-TS over RTP is significantly different beast than
RTP-muxed elementary streams.

In any case, for MPEG-TS over RTP we need to be sure that VLC executes
the special clock-synchro algorithm, which ensures that VLC's internal
reference clock is synchronized to the sender's clock. This however
requires precise passing of packets to synchro at correct time points.
The special 100 ms *time-driven* RTP reordering buffer at access level
was the only solid solution that kept the synchro happy. This is the
most important part, some years ago we spent here several hours before
we got it working right. 

For the same reasons, prebuffering needs to be disabled for both UDP and RTP,
which doesn't seem to be the case again with 0.9.x. With prebuffering (which
is kB based and not time-based), VBR streams confuse VLC's internal reference
clock to the point that it starts up/downsampling or drops audio packets
at big scene changes.

    With kind regards,


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----   Marian Ďurkovič                       network  manager         ----
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