VDR recordings/timeshift and teletext

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FernetMenta Offline
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Post: #16
What you are saying makes sense and points to an issue of vdr. Recording is done by vdr only. I try to give some background information for you to get a notion of what's happening here.
The data is broadcasted as mpegts. Video, audio, subs, text is sent in small packets of 188bytes identified by a PID (packet identifier). On a given frequency there may be many PIDs of different channels. In order to know what PIDs belong to a channel there is PAT/PMT. Those tables define what PIDs belong to a service id of a program. Take a look into channels.conf (http://www.vdr-wiki.de/wiki/index.php/Vd...9#CHANNELS). vdr parses PAT/PMT and writes the PIDs into channels.conf. If UpdateChannels (setup.conf) is > 3, vdr updates those PIDs.

When watching live tv VNSI handles this. You tune to a channels, vnsi waits for a valid PAT/PMT, parses PIDs, and tells vdr what PIDs it wants to receive. Now the tricky part: PIDs may change. Suppose a movie starts and the broadcaster adds an additional audio and subtitle stream. vnsi detects this but there is a weakness in design of vdr. It does not allow to dynamically add or remove PIDs once the receiver is attached to the dvb device. VNSI needs to detach/attach, then signal XBMC a change of streams so XBMC can open required decoders.

When it comes to recordings all is handled by vdr. We only set a timer which tells vdr what to start recording of the desired channel. When the time comes vdr will start recording the PIDs associated to a channels (without teletext) at this time. I have not looked into vdr code but I think it misses any PID added later. Means if you start your recording too early or you don't allow update of PIDs, your recoding does not contain those streams.
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tonalt Offline
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Post: #17
(2014-05-11 08:28)FernetMenta Wrote:  What you are saying makes sense and points to an issue of vdr. ...
I try to give some background information for you to get a notion of what's happening here.

That's sounds great in every respect ... I'm very happy about your remarks ...

A supplement to your technical explanation; don't know if my remark is of any value:
I switched to BBC (xbmc client with activated vnsi addon) and watched a film with subtitles ... asked myself if the PID stuff shouldn't be set now in a correct manner ... so i pushed the "record-button" in the command line of the live tv window. Unfortunately the recorded stream doesn't seam to contain the subtitles ...
(This post was last modified: 2014-05-11 14:49 by tonalt.)
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