sdp.h

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#pragma once
 
/* Storage capacities in elements; text buffers include the terminating NUL. */
#define NETWORK_WEBRTC_SDP_SESSION_ID_BUFFER_SIZE 32
#define NETWORK_WEBRTC_SDP_SESSION_VERSION_BUFFER_SIZE 16
#define NETWORK_WEBRTC_SDP_SDP_STRING_BUFFER_SIZE 4096
 
#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>
#include "../../common.h"
#include "../../asciichat_errno.h"
#include "../../media/codecs.h"
 
#ifdef __cplusplus
extern "C" {
#endif
 
/* ============================================================================
 * Audio Codec Configuration
 * ============================================================================ */

typedef struct {
  uint32_t sample_rate;    
  uint8_t channels;        
  uint32_t bitrate;        
  uint16_t frame_duration; 
  bool dtx_enabled;        
  bool fec_enabled;        
} opus_config_t;
 
/* ============================================================================
 * Terminal Rendering Capability "Codecs"
 * ============================================================================ */

typedef enum {
  ACIP_CODEC_TRUECOLOR = 96, 
  ACIP_CODEC_256COLOR = 97,  
  ACIP_CODEC_16COLOR = 98,   
  ACIP_CODEC_MONO = 99,      
} acip_codec_t;

typedef struct {
  uint16_t width;  
  uint16_t height; 
  enum { RENDERER_BLOCK, RENDERER_HALFBLOCK, RENDERER_BRAILLE } renderer;
  enum { CHARSET_ASCII, CHARSET_UTF8, CHARSET_UTF8_WIDE } charset;
  enum { COMPRESSION_NONE, COMPRESSION_RLE, COMPRESSION_ZSTD } compression;
  bool csi_rep_support;     
  const char *palette_hint; 
} terminal_format_params_t;

typedef struct {
  acip_codec_t codec;              
  terminal_format_params_t format; 
} terminal_capability_t;
 
/* ============================================================================
 * SDP Session Description
 * ============================================================================ */

typedef struct {
  /* Session-level attributes */
  char session_id[NETWORK_WEBRTC_SDP_SESSION_ID_BUFFER_SIZE];           
  char session_version[NETWORK_WEBRTC_SDP_SESSION_VERSION_BUFFER_SIZE]; 
 
  /* Audio media section */
  bool has_audio;                    
  opus_config_t audio_config;        
  uint32_t codec_capabilities_audio; 
 
  /* Video media section (terminal capabilities) */
  bool has_video;                        
  terminal_capability_t *video_codecs;   
  size_t video_codec_count;              
  terminal_format_params_t video_format; 
  uint32_t codec_capabilities_video;     
 
  /* Raw SDP string (generated from above) */
  char sdp_string[NETWORK_WEBRTC_SDP_SDP_STRING_BUFFER_SIZE]; 
  size_t sdp_length;                                          
} sdp_session_t;
 
/* ============================================================================
 * SDP Generation (Offer/Answer)
 * ============================================================================ */

asciichat_error_t sdp_generate_offer(const terminal_capability_t *capabilities, size_t capability_count,
                                     const opus_config_t *audio_config, const terminal_format_params_t *format,
                                     uint32_t video_codec_caps, uint32_t audio_codec_caps, sdp_session_t *offer_out);

asciichat_error_t sdp_generate_answer(const sdp_session_t *offer, const terminal_capability_t *server_capabilities,
                                      size_t server_capability_count, const opus_config_t *audio_config,
                                      const terminal_format_params_t *server_format, uint32_t server_video_codec_caps,
                                      uint32_t server_audio_codec_caps, sdp_session_t *answer_out);
 
/* ============================================================================
 * SDP Parsing (Offer/Answer)
 * ============================================================================ */

asciichat_error_t sdp_parse(const char *sdp_string, sdp_session_t *session);

asciichat_error_t sdp_get_selected_video_codec(const sdp_session_t *answer, acip_codec_t *selected_codec,
                                               terminal_format_params_t *selected_format);
 
/* ============================================================================
 * Capability Detection
 * ============================================================================ */

asciichat_error_t sdp_detect_terminal_capabilities(terminal_capability_t *capabilities, size_t capability_count,
                                                   size_t *detected_count);
 
/* ============================================================================
 * Utility Functions
 * ============================================================================ */

void sdp_session_destroy(sdp_session_t *session);

const char *sdp_codec_name(acip_codec_t codec);

const char *sdp_renderer_name(int renderer_type);
 
#ifdef __cplusplus
}
#endif