[vdr] cReceiver vs cFilter and PTS questions

Patrick Fischer patrick_fischer at gmx.de
Fri Nov 4 17:02:18 CET 2005


Udo Richter schrieb:

>Patrick Fischer wrote:
>  
>
>>2. I want to get the PTS from the current V-PID. I have looked at the
>>femon Plugin. This use a cReceiver which gives me an repacked TS with
>>188byts. I have surched for a Spec. which gives me more informations
>>about the 188Byts.
>>The first 16bit (12bit used) are the PID
>>8bit are the (PAYLOAD/ADAPT_FIELD)(don't know what it is)
>>8bit some kind of offset
>>......
>>    
>>
>
>The mpeg-TS format (and all the other mpeg sream formats) is specified
>in ISO/IEC 13181-1.
>
>The difficult thing about these mpeg formats is that often unused parts
>of the headers get skipped, which causes all data behind the hidden part
>to move forward. In case of TS, the layout changes depending on whether
>the adaption field exists or not. (ADAPT_FIELD flag, officially called
>adaption_field_control)
>
>TS packets can contain an adaption field and/or payload, depending on
>adaption_field_control. If the adaption field exists, its first byte is
>adaption_field_length, your 'some kind of offset'. Payload will be right
>after the adaption field, if present, and is usually a PES stream.
>
>However, the PTS is not in the TS headers. The PTS first appears in the
>PES packet headers. Not every PES header has a PTS entry, you have to
>check the stream_id and the PTS_DTS_flags field...
>
>  
>
Thanks. So i have to check more then the ADAPT_FIELD. I will fix my version.

>>3. I want to get all PTS from all V-PID's on the transponder. Is it
>>possible?
>>    
>>
>
>You would have to receive all the video streams of that transponder at
>the same time. May cause trouble with the PID filters and with the data
>throughput.
>  
>
I think the PID's will not make problems. Each PID is unique for a 
videostream of the transponder. But with the throughput you are rigth. I 
need an other idea. Maybe I can listen to 2-3 PID's and skip always one 
of them.

Patrick



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