Adding support for H264

[diegonunes4]

Hello!
Me and @massis08 work at @bisect-pt and we are adding support for a new media type, currently H264 but we are also planning to add to H265, and we are facing some challenges and would like to ask for some guidance!

FYI we are following the steps on #225.

We started by adding a struct called video_H264_parameters, and since all the parameters are optional, we only added the most important ones, packetization mode, profile level id and sprop parameter sets, (in the future more could be added).

After this we were looking at make_video_H264_parameters and were confused about the usage of the nmos::fields, do we need to add the new H264 fields to this nmos::fields namespace or that should be on another place since they are not used in any type of device?

Thank you!

[diegonunes4]

After some more research we went ahead and developed the make_video_H264_sdp_parameters like this:

    sdp_parameters make_video_H264_sdp_parameters(const utility::string_t& session_name, const video_H264_parameters& params, uint64_t payload_type, const std::vector<utility::string_t>& media_stream_ids, const std::vector<sdp_parameters::ts_refclk_t>& ts_refclk)
    {
        sdp_parameters::rtpmap_t rtpmap = { payload_type, U("H264"), 90000 };

        sdp_parameters::fmtp_t fmtp = {
                { sdp::fields::profile_level_id, utility::ostringstreamed(params.profile_level_id) },
                { sdp::fields::packetization_mode, utility::ostringstreamed(params.packetization_mode) },
                { sdp::fields::sprop_parameter_sets, utility::ostringstreamed(params.sprop_parameter_sets)}
        };

        return{ session_name, sdp::media_types::video, rtpmap, fmtp, {}, {}, {}, {}, media_stream_ids, ts_refclk };
    }

Is this the correct approach?

[garethsb]

Hi @diegonunes4, this first bit looks right to me. I'm going to need this myself very soon, so if you want to talk it through, @pedro-alves-ferreira knows how to get hold of me :-)

[diegonunes4]

Thank you for you help @garethsb, I will leave here the link to my forked repository so you can take a look at the code.
https://github.com/diegonunes4/nmos-cpp

[garethsb]

Thanks. I've added some initial commit comments here: diegonunes4@9dc253c. GitHub will make it easier for us to review if you make your changes on a branch in your fork and then make a PR either here or just onto master in your own fork.