I am currently streaming audio (AAC-HBR at 8kHz) and video (H264) using RTP. Both feeds works fine individually, but when put together they get out of sync pretty fast (lass than 15 sec).
I am not sure how to increment the time stamp on the audio RTP header, I thought it should be the time difference between two RTP packets (around 127ms) or a constant increment of 1/8000 (0.125 ms). But neither worked, instead I managed to find a sweet spot. When I increment the time stamp by 935 for each packet It stays synchronized for about a minute.
AAC frame size is 1024 samples. Try to increment by (1/8000) * 1024 = 128 ms. Or a multiple of that in case your packet has multiple AAC frames.
Does that help?