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> NULL Stuffing algo & Multicast out bitrate increased by 1.1111
Guest_Aniket A. Salunkhe_*
post Nov 5 2012, 11:05 PM
Post #1


Hi All,

I am trying to develop a software based re-multiplexing (LINUX &/or WINDOWS). The flow of my solution is as follows,

Multicast Input (7 packets at a time .... getting loss of packet if read one packet at a time)
--> De-multiplexing (one packet at time, removing incoming NULL packets)
--> PID Remapping (optional, per packet PID remapping)
--> CBR (can say as NULL packets insertion if FIFO is empty, timing based on output bitrate)
--> PCR re-stamping (based on output bitrate changing in incoming PCR values per packet if PCR exist)
--> Multicast Output (7 packets at a time)

I have used pthreads for each of above operation, and pthread_mutex for synchronization among FIFOs of those threads;
and used clock_gettime() to generate a tick for a packet for NULL insertion based on empty FIFO and even for maintaining output bitrate.

I have provided a multicast input by multicasting a local file (by VLC or WinSend tool) from other system. File has total bitrate around 19Kbps, having 15Kbps NULL packets in it.
CASE A] When I am checking multicast output with incoming NULL removal and new NULL insertion getting increasing "PCR repetition erros" (checked StreamXpress tool). Also output bitrate is displayed in multiple of around 1.1111 ratio.
CASE B] but when I disabled NULL packet insertion and passed incoming NULL packets as it is, but keeping PCR re-stamping, getting smooth output without any errors; but output bitrate is still in ratio of around 1.1111.

I checked PCR location in CASE B (it means in incoming stream too), PCR are uniformly located.
But for CASE A (my NULL packet insertion solution), PCR are not uniform.

Even after scratching my head for many days I didn't get any solution or source of problem. Please help me to solve this problem.

For information, I have written code using C language on Fedora 16 and running of Quad-core system.

Thanks in advance.
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