[vdr] Mux A / Channel 5 UK DVB-T broken with VDR, dvbstream works...

[Gregor Lawatscheck <gpel@mpex.net>]

There appears to be a bug handling MPEG streams from the UK DVB-T Multiplex 
A (mux A) with vdr. I've tested versions 1.0.4, 1.1.13, 1.1.16 and 1.1.20 
with the old and NEWSTRUCT drivers. All other Multiplexes are fine (both 
QAM16 and QAM 64 ones).

Mux A in the UK most importantly carries Channel 5 (C5) and (up until Jan 
13) Sky News and no matter how good a tuning I manage to adjust, I get 
constant cut-outs in the stream. It's not the usual blockiness or freeze in 
the picture when the reception is bad but it looks more like some of the 
pictures are repeated in succession (syncing problem? buffer?). The 
cut-outs are especially noticable in fast movements like sports coverage. 
Unfortunately vdr doesn't output any special errors related to this to the 
message log.

Using dvbstream to output to a fifo-file and playing back this fifo-file in 
realtime with mplayer to -ao mpegpes -vo mpegpes works fine (!!) and 
without any cut-outs or repeated images in the stream. Recording files from 
C5 in vdr and then playing them back in mplayer to -ao / -vo mpegpes shows 
the same errors as watching the channel live in vdr. Strange isn't it... I 
seriously didn't think this could be caused by vdr and faffed about with 
the tuning on and off through the past few months...

The fact it reproducibly works fine with dvbstream -> fifo -> mplayer -> 
DVB-S card but fails in vdr makes me think the error must lie with vdr 
rather than with the driver or the tuning or anything else! I have 
double-checked QAM, FEC, transmission mode, guard interval and bandwidth 
settings to correspond between dvbstream and the vdr config for the mux in 
question. What I'm wondering is why ( at least in the past year) no one 
else seems to have noticed any problems regarding Channel 5 and DVB-T using 
vdr? Are you all blaming your tuning or is it just that no one else can 
reproduce this problem? I'm using the Oxford transmitter if that is of any 
value. I've googled and searched the vdr-mailinglist without finding 
reports about any similar stories.

What would be the best way to debug this? I'm willing to help and go 
through source-code if other people can reproduce this and give me some 
pointers. Let's get this fixed...

- Gregor



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