[FFmpeg-user] ffserver HTTP stream playback freeze

Stefano Sabatini stefasab at gmail.com
Fri Dec 20 18:23:56 CET 2013

On date Friday 2013-12-20 08:12:29 +0100, Nicolas George wrote:
> Le decadi 30 frimaire, an CCXXII, Stefano Sabatini a écrit :
> > Works fine in my internal network and in an external one, freeze
> > issues observed in two external networks. TCP debugging with wireshark
> > shows that the freeze occurrs just after a TCP ZeroWindow event on the
> > client side, then for some reasons the server stops to react and won't
> > send new packets.

> You mean: the client sends ZeroWindow to the server and the server stops
> reacting? At a wild guess, I would say that ZeroWindow will cause a system
> call to block on the server instead of succeeding immediately, and that
> could be handled wrong in ffserver code: the socket could be in non-blocking
> mode, the system call returns EAGAIN, and ffserver treats it partially as a
> permanent error.

I don't think so, the issue cannot be reproduced systematically, I got
the freeze only in particular networks (2 over 3 tested), and never on
my local network. So it seems it is somehow related to the tested
network (and seems more a problem at the network level rather than at
the application level, where I can't see apparent errors).

The ZeroWindow event usually triggers the condition where after some
short time I see no packets from the server, nor the connection is
closed, so that no data is fed to the client and it seems to hang.

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