Hello, DVBCUT users.

I just wanted to keep you up to date, as it seems that I found (and fixed) two 
bugs, which could be responsible for the problems posted recently to this 
mailingslist.

First: as I said in my last posting, I could reproduce a segfault when working 
on streams from German public TV stations. I could track it down to an oddity 
in the timestamps in the original streams. In contrast to the streams I used 
before, here the MPEG audio frames (smallest unit of audio, 1152 samples) are 
sometimes placed accross packet boundaries. This should not be a problem, my 
stream parser does not rely on audio PES packets always starting with an 
audio frame (although they do, on MTV2), but the audio packets on ARD that 
start amidst MPEG audio frames bear wrong timestamps, slightly off from the 
correct ones. This caused quite some trouble, because for DVBCUT the 
timestamps were not in sequence anymore. From my point of view, this is a 
violation of the ISO standard, as PTS should represent the time of 
presentation of the first MPEG audio frame commencing in the packet. Anyway, 
I changed DVBCUT such that timestamps of audio packets are ignored when the 
"data alignment indicator" is not set, that is, if the packet does not begin 
with a beginning of an audio frame.

Second: regarding the negative time codes displayed by DVBCUT. I found that 
some TV stations (Kabel 1, in my example) only have 32 bit timestamps. The 
timestamp fields in MPEG2 streams comprise 33 bits. However, here only 32 
bits are used, such that 2^32-1 is followed by 0, not by 2^32. This happens 
approximately every 13 1/4 hours. If you use all 33 bits, unique timestamps 
last 26 1/2 hours. This is fixed as well, DVBCUT regards 0 now as 2^32 when 
it follows values close to 2^32.

Okay. I'm planning to make a new release at the weekend. I hope I will fix 
some more bugs and include more improvements by then.

Bye...

-- 
Sven Over
Stephanienstr. 9
76133 Karlsruhe

Telefon: 0721-9204199

http://www.svenover.de/


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