[vdr] Frame detector glitch

Klaus Schmidinger Klaus.Schmidinger at tvdr.de
Tue Jan 14 10:21:39 CET 2014


On 13.01.2014 21:38, Eike wrote:
> Hello!
>
> I'm experiencing what I'd call a glitch of VDR's frame detector class.
>
> There's a define #define MIN_TS_PACKETS_FOR_FRAME_DETECTOR 5.
> According to my experiences, this number of TS packages in not always
> enough to detect frames as early as possible. Thus it is a matter of chance
> if detection will be fed with enough data to detect the first frame or if it
> will glitch through to another one. I think we should avoid such situations.
>
> I attached demo code (needs some includes and to be compiled and linked
> with VDR) which shows the behaviour and I stored a short TS sample at
> http://ein-eike.de/wordpress/wp-content/uploads/2014/01/vdr-sample.ts
> The code checks when an I frame is found, at first with full data available,
> and then with data dripping in with a frame size of 5, 6 ... until the
> dripping data yields the same result as the flooding data.
>
> I get the following output from the given example:
>
> Checking file at offset 0
> Without frame limit... Found I frame after 190256 bytes
> With frame limit 5... Found I frame after 398560 bytes
> With frame limit 6... Found I frame after 190256 bytes
> TS package frame size needed for this video block: 6
> Maximum TS package frame size needed for this video recording: 6
>
> Unfortunately, I cannot tell if 6 is the definite number to avoid such glitches
> or if other circumstances would need a higher number. I wrote the code such
> as people might try it out on their video files so we could experiment.
> (I could provide a Linux executable as well.)

Can you name a satellite channel where this problem occurs?

Klaus



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