In a call, I am receiving H.264 data in RTP packet.
I need to write it to a mkv file to and then I should be able to play it
It looks that I am always getting single NAL unit in RTP packet.
My understanding is, I need to remove RTP packetization data (rfc 6184),
and remove immediate next byte (F | NRI | TYPE), and then write remaining
data to file prefixed with 0x00 0x00 00x1.
After I prepare buffer, then I use av_write_xxx apis to write it using