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. > 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. :) > 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? 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 > -- -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
