[mythtv] dvb zero length record

Phil Vid phil.vid at gmail.com
Mon Jun 6 10:56:31 UTC 2005

More updates..

> 1. Blank recording, nothing obvious in the logs case 1. This appears
> to be a keyframe detection problem. The recordings enter the
> ReadFromDMX() loop but silently exit as no keyframe has been detected.
> The obvious symptom of this is the absence of the message 'DVB#x Found
> keyframe' in the log. I will investigate this first as this is the
> cause of 90% of my zero byte recordings.

This has been resolved by turning off the 'Wait for SEQ Start Header'
flag in the DVB card setup. Thanks Will Uther for suggesting this fix.
Unfortunately I don't have any experience with MPEG video stream
decoding, so is anyone able to explain why this is necessary and what
the purpose of the sequence frame wait is?

> 2. Blank recording, nothing obvious in the logs case 2. Problem with
> PMT/CAM or not authorised to view. The recording enters the
> ReadFromDMX() loop but silently exits upon receiving scrambled
> packets. Easy to detect with an additional debug line upon exit, after
> fixing case 1 hopefully this case can be remedied with some additional
> resends of the PMT.

Am still seeing these, they tend to appear after about 3 days of
successful recording of encrypted content. I've tried a hack to resend
the PMT and this doesnt appear to be the solution. More debugging

> 3. DVB#x WARNING - No data received ... This one I'm not sure about at
> all. It doesnt appear to be CAM related, have tested by replaying the
> correct PMT back to the CAM upon receiving this error message.

Not seen this one since my last post :)


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