[mpeg2] Doubts with SCR and Timing MPEG-2

Alexandre Vazquez alexandre.vazquez at gmail.com
Sun Mar 2 21:19:07 CET 2008


   
Hi,

I'm writing to you, because I have a doubt with some fields in the 13138 - 1 
MPEG-2 ISO . The doubt it's related with some piece of code, but that 
envolves concept problems  about MPEG, because of this, the mail is in the 
list.

Ok, the code I'll talk about is the dvb-mpegtools (used to many programs) and 
now inside the libdvb.

I need to calculate the SCR from the parameters I have in the Transport 
Stream, and in the PES packages ,I can see in the code.. something like this 
(line 1512 of transform.c ) :

SCR = trans_pts_dts(p->pts)-3600; 

I would know the relation between SCR and PTS/DTS and the meaning of that 
3600.

the code of the function trans_pts_dts is the following:

uint32_t trans_pts_dts(uint8_t *pts)
{
        uint32_t wts;
        
        wts = (((pts[0] & 0x06) << 4) | 
               ((pts[1] & 0xFC) >> 2)) << 24; 
        wts |= (((pts[1] & 0x03) << 6) |
                ((pts[2] & 0xFC) >> 2)) << 16; 
        wts |= (((pts[2] & 0x02) << 6) |
                ((pts[3] & 0xFE) >> 1)) << 8;
        wts |= (((pts[3] & 0x01) << 7) |
                ((pts[4] & 0xFE) >> 1));
        return wts;
}

I can't know the reference of that hexadecimal numbers.. in the ISO .. If 
anyone know the meaning of that numbers , please tell me.


That's all for now.. I send you the code  of mpegtools .

Thanks for all .


P.S. For problems with the attachments, I only send you the transform.c/.h 
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