|
Hi Vinay:
This is the typical MPEG-2 Systems way to indicate that the length is not explicitly specified in the syntax. However, it can be easily inferred that this loop cannot take more than (section_length - 9) bytes. (9 = 5 bytes after the section_length field + 4 bytes of CRC at the bottom of the section). The section length cannot exceed 1021 bytes so this further constrains the number of iterations (no more than (1021-9) / 4 = 253 programs can be listed in the section ). So, N <= 253.
While I am at it, I will encourage you to buy the following book (I am one of the authors). It includes a nice intro to MPEG-2 systems where all this kind of stuff is already resolved for you. The title is: Data Broadcasting: Understanding the ATSC Data Broadcast Standard
Kind regards,
Regis.
================================================ Regis J. Crinon, Ph.D. Lead Program Manager, Core Media Processing Technologies Windows Digital Media Division Microsoft Corporation One Microsoft Way Building 50 - Office 3509 Redmond WA 98052-6399 USA Tel: 425-707-3475 Fax: 425-936-7329 ================================================
-----Original Message-----
hi
I m a newbie to DVB-RCS.While trying to get the Program map PIDs, for the different programs,from the PAT table, a variable N is presented in the standard, saying that so many program channels are present.But, I have not found any place/hint indicating what this variable n might be? The exact context is given below.(marked by the Arrow)
program_association_table program_association_section() { table_id 8 uimsbf section_syntax_indicator 1 bslbf '0' 1 bslbf reserved 2 bslbf section_length 12 uimsbf transport_stream_id 16 uimsbf reserved 2 bslbf version_number 5 uimsbf current_next_indicator 1 bslbf section_number 8 uimsbf last_section_number 8 uimsbf
for (i = 0; i < N; i++) -------------------->what is the value of N? { program_number 16 uimsbf reserved 3 bslbf if (program_number = = '0') { network_PID 13 uimsbf } else { program_map_PID 13 uimsbf } } CRC_32 32 rpchof }
with warm regards, Vinay.S
|