AVCodec (ffmpeg) cannot decode slice header when parsing h264 after getting new SPS and PPS, why?

Question

C++ / C#

Greetings.
Scrap rtsp, get h264 stream from rtp, collect frames - everything is ok.
I save the frames to a file (*.h264) to make sure that everything is ok - VLC plays quietly (I also tried to convert the file via ffmpeg to AVI - the same is all ok - the whole conversion is without errors)
But if in runtime I decode by frames with help

avcodec_decode_video2(m_decoderContext, m_picture, &got_picture, &m_packet);

decodes normally for the first 10 seconds BEFORE new SPS and PPS arrive (the camera switches to night mode)
as soon as they come from avcodec only errors:

decode_slice_header error
concealing 1497 DC, 1497 AC, 1497 MV errors in P frame

Why is this happening and in what direction to dig?
it seems that avcodec does not process new sps and pps...

Answer 1

The problem was in the speed of parsing and the small size of their buffer.