source_impl.h

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/* -*- c++ -*- */
/*
 * Copyright 2026 Franco Venturi.
 *
 * based on:
 * - pcmcat in ka9q-radio
 * - wavfile_source block in GNU Radio
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 */
 
#ifndef INCLUDED_RTP_SOURCE_IMPL_H
#define INCLUDED_RTP_SOURCE_IMPL_H
 
#include <gnuradio/rtp/source.h>
 
extern "C" {
#include "multicast.h"
#include "rtp.h"
}
 
#define FULL_SAMPRATE (48000)
 
namespace gr {
namespace rtp {
 
struct pcmstream {
  uint32_t ssrc;            // RTP Sending Source ID
  int type;                 // RTP type (10,11,20)
 
  struct sockaddr sender;
  char const *source;
  int framesize;            // Bytes per timestamp increment
 
  long long bytes_received;
  struct rtp_header last_header;
  int last_size;
};
 
template <class T>
class source_impl : public source<T>
{
private:
    int mcast_fd;
    struct pcmstream pcmstream;
    unsigned int ssrc; // Requested SSRC
    int channels;
    bool quiet;
 
public:
    source_impl(const std::string& mcast_address,
                unsigned int ssrc,
                int in_channels=1,
                int out_channels=1,
                bool quiet=false);
    ~source_impl();
 
    int get_bits_per_sample() const override {
        return sizeof(std::int16_t) * 8;
    }
 
    int get_channels() const override { return channels; };
 
    void set_ssrc(unsigned int ssrc) override {
        this->ssrc = ssrc;
        pcmstream.ssrc = 0;
    };
 
    unsigned int get_ssrc() const override { return ssrc; };
 
    int work(int noutput_items,
             gr_vector_const_void_star& input_items,
             gr_vector_void_star& output_items);
 
private:
    void check_out_channels(int channels) const { return; }
    int get_output_items(int sampcount, int channels, int noutput_channels, int time_step) const {
        return time_step + sampcount / channels;  // == sampcount for mono, sampcount/2 for stereo
    }
    int output_zeroes(int nzeroes, int channels, T** outs,
                      int noutput_items, int noutput_channels,
                      int offset = 0) const;
    int output_samples(const void *dp, int size, int channels, T** outs,
                       int noutput_items, int noutput_channels,
                       int offset = 0) const;
 
};
 
} // namespace rtp
} // namespace gr
 
#endif /* INCLUDED_RTP_SOURCE_IMPL_H */