Am 04.02.2010 08:25, schrieb Hans Verkuil:
On Thursday 04 February 2010 04:16:03 Andy Walls wrote:
On Thu, 2010-02-04 at 01:18 +0100, Lars Hanisch wrote:
Hi,
I'm writing some code repacking the program stream that ivtv delivers
into a transport stream (BTW: is there existing code for this?).
Buy a CX23418 based board. That chip's firmware can produce a TS.
I think Compro and LeadTek cards are available in Europe and are
supported by the cx18 driver.
My PVR150 and 350 are still ok and I hope I have DVB-S-access in one
or two years... But I will keep that in mind in case I need a new card.
Since
many players needs the PCR I would like to use the SCR of the PS and
place it in the adaption field of the TS (if wikipedia [1] and my
interpretation of it is correct it should be the same).
I stumbled upon the ps-analyzer.cpp in the test-directory of the
ivtv-utils (1.4.0). From line 190 to 198 the SCR and SCR extension are
extracted from the PS-header. But referring to [2] the SCR extension has
9 bits, the highest 2 bits in the fifth byte after the sync bytes and
the lower 7 bits in the sixth byte. The last bit is a marker bit (always 1).
So instead of
scr_ext = (hdr[4]& 0x1)<< 8;
scr_ext |= hdr[5];
I think it should be
scr_ext = (unsigned)(hdr[4]& 0x3)<< 7;
scr_ext |= (hdr[5]& 0xfe)>> 1;
Given the non-authoritative MPEG-2 documents I have, yes, you appear to
be correct on this.
Please keep in mind that ps-analyzer.cpp is simply a debug tool from an
ivtv developer perspective. You base prodcution software off of it at
your own risk. :)
Of course I will. :-) I already had coded my part and was looking for
references...
And the bitrate is coded in the next 22 bits, so it should be
mux_rate = (unsigned)(hdr[6])<< 14;
mux_rate |= (unsigned)(hdr[7])<< 6;
mux_rate |= (unsigned)(hdr[8]& 0xfc)>> 2;
Am I correct?
Yes, you are correct. I miscounted the bits when I wrote this originally.
Thanks for reporting this!
You're welcome!
Regards,
Lars.
Regards,
Hans
I did not check this one, but I would not be surprised if ps-analyzer
had this wrong too.
Regards,
Andy
Regards,
Lars.
[1] http://en.wikipedia.org/wiki/Presentation_time_stamp
[2] http://en.wikipedia.org/wiki/MPEG_program_stream
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