How to get H264 SPS & PPS data?

[paulomorgado]

Image processing is not my thing.

I'm just trying to change some code to use this library and, to decode the frame using ffmpeg, apparently, I need SPS and PPS segments.

What am I missing here?

[ngraziano]

Hi,

If you are using the RtspClientExample you will see at line 332 in Program.cs an exemple to get the SPS and PPS

SharpRTSP/RtspClientExample/Program.cs

Lines 330 to 334 in 9f190fa

	if (args.StreamConfigurationData is H264StreamConfigurationData h264StreamConfigurationData)
	{
	WriteNalToFile(fs_v, h264StreamConfigurationData.SPS);
	WriteNalToFile(fs_v, h264StreamConfigurationData.PPS);
	}

They are byte array. They do not contain the 00 00 00 01 NAL header which is sometime needed.

This value come from the SDP response to the DESCRIBE command. you can follow the code in RTSPClient.cs how we get them.
Some camera send the SPS and PPS inn band i.e. in the RTP packet as a NAL you will have to check the type of the type like that

SharpRTSP/RtspClientExample/Program.cs

Lines 343 to 354 in 9f190fa

	int nal_ref_idc = (nalUnit[4] >> 5) & 0x03;
	int nal_unit_type = nalUnit[4] & 0x1F;
	string description = nal_unit_type switch
	{
	1 => "NON IDR NAL",
	5 => "IDR NAL",
	6 => "SEI NAL",
	7 => "SPS NAL",
	8 => "PPS NAL",
	9 => "ACCESS UNIT DELIMITER NAL",
	_ => "OTHER NAL",
	};

[paulomorgado]

Got it! Thank you so much!