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stuttering or aborting video stream (refs #2045)
Toerless Eckert wrote:
This patch tries to resolve problems in streamdev-client that
can occur when enabling "StreamFilters". Enabling this option
is necessary to receive certain programs with dynamic PIDs such as
some german "regional" broadcast (eg: NDR).
Problem:
Without this fix, the following behavior was observed on a Raspberry
PI running streamdev-0.6.1-git with VDR-2.6.1:
- Buffer overflows of filter data
- Stop/go video on channels
- Total stopping of video
More logs in:
http://www.vdr-portal.de/board16-video-disk-recorder/board55-vdr-plugins/125237-
streamdev-client-filter-daten-streamen-ndr-raspberry-haengt/
Analysis:
VDR expect section data from filters separately from the
main program stream. Historically, it received each filter data
via a separate file descriptor from the DVB card. In the streamdev-client
module, a socketpair is used to feed filter data to the main VDR code.
During certain operations in VDR, such as startup or channel change
(depending also on the speed of initialization of the video output driver),
VDR does not consume the filter data as fast as it is provided by
streamdev-client, resulting in overflow of the default socket buffers
used by streamdev-client.
To add to the problem of overflowing the socketpair buffers, the
streamdev-client code sends several times a second short packets into
the socketpair to determine if the receiving side (VDR) has closed
the socketpair (IsClosed(), CarbageCollect()). This further clogs
up the socketpair() buffer.
The raspberry PI socketpair buffering behavior seems to be the same
as that of other 3.x linux systems, the socket buffer size is by
default 163840, and it can be increased via sysctl net.core.wmem_max.
During startup, it can take up to 10 seconds before VDR will consume
filter data, so the socketpair buffer can fill up with 10 seconds worth
of data.
Solution
1. IsClosed()/CarbageCollect() where removed from client/filter.c
and replaced by explicitly tracking when VDR closes a filter socket.
This alone seems to already resolve the problem of hanging or stop&go
video and seems to be sufficient to receive dynamic-PID channels reliably.
2. filter.c was enhanced to request a larger socket buffer size
if config option FilterSockBufSize is set.
3. If supported (if streamdev-client runs on linux), the socketpair
queue is "flushed" to reduce the amount of "random" packet drop messages
and to rather drop sequential messages.
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Modified Files:
client/filter.c server/livefilter.c
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- dropped patches for pre VDR 1.4
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- regonize PUSI flag in TS packets (bullet-proof section start+end indicator)
- Use own TS buffer to read directly from socket, no need for ring buffer anymore
- Re-activate all active filters after re-connection to server
- Simplify thread start/stop/running detection to current VDR style
- Update "filter closed by VDR" detection (datagram sockets
return different errno's than pipes)
- Deliver data to first matching and active filter (do not drop data if first
matching filter has been closed, there is quite likely new filter for it)
- Add disconnect detection to avoid 100% CPU usage in cTSBuffer::Action()
Modified Files:
client/filter.c client/filter.h
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- Run section filter carbage collector when adding new filter.
Carbage collector closes all filters that have already been
closed by local VDR section handler.
(without this, closed section filters are removed only when
they receive data from server. If they wont, ...).
- Add locking to list handling (list is accessed from separate threads)
Modified Files:
client/filter.c client/filter.h
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- Reset section data unpacker only after first non-full TS packet
(last TS packet of section is typically not full
- Do not close filter if socket buffer is full (EAGAIN, EWOULDBLOCK)
(closing results in 100% CPU usage in VDR section handler)
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- Do not close receiving side of section pipe. Ownership of handle
has been transferred to VDR section handler when filter was opened.
Closing handle twice results closing random file handle. If this
handle is laready used by another section filter pipe (very likely),
VDR section handler CPU usage will rise to 100%.
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- Use datagram mode socket instead of pipe to feed
section data to client VDR section handler
-> preserve section data block boundaries
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- Move cStreamdevFilter definition from filter.h to filter.c
- Add IsClosed() and Reset() members to cStreamdevFilter:
* IsClosed() returns true if filter was closed by VDR
* Reset() discards (incomplete) queued section data
Modified Files:
client/filter.c client/filter.h
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