CDDA Playback via Digital-Audio-Extraction on Linux w/SDL3

cdda.c

// Super-hacky CD player with SDL3 and the CDROMREADAUDIO ioctl.

#include <linux/cdrom.h>

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdint.h>
#include <sys/ioctl.h>

#include <SDL3/SDL.h>

#define SECTORS_AT_ONCE 4
#define MAX_SECTORS_BUFFERED 10

int main(int argc, char **argv)
{
	SDL_Init(SDL_INIT_AUDIO);

	SDL_AudioSpec cdda_spec = { .format = SDL_AUDIO_S16LE, .channels = 2, .freq = 44100 };
	SDL_AudioStream *stream = SDL_OpenAudioDeviceStream(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, &cdda_spec, NULL, NULL);

	int cdrom = open("/dev/cdrom", 0);
	
	struct cdrom_tochdr toc;
	ioctl(cdrom, CDROMREADTOCHDR, &toc);
	printf("First track %d, last track %d\n", toc.cdth_trk0, toc.cdth_trk1);
	for (uint8_t track = toc.cdth_trk0; track < toc.cdth_trk1; ++track)
	{
		struct cdrom_tocentry toce;
		toce.cdte_track = track;
		toce.cdte_format = CDROM_MSF;
		ioctl(cdrom, CDROMREADTOCENTRY, &toce);
		printf("Track %d, addr = %02d:%02d:%02d, %s\n", track, toce.cdte_addr.msf.minute, toce.cdte_addr.msf.second, toce.cdte_addr.msf.frame, (toce.cdte_ctrl & CDROM_DATA_TRACK) ? "Data" : "Audio");
	}

	SDL_ResumeAudioStreamDevice(stream);
	struct cdrom_read_audio readaudio = {0};
	readaudio.nframes = SECTORS_AT_ONCE;
	readaudio.addr_format = CDROM_LBA;
	while (true)
	{
		uint8_t buf[CD_FRAMESIZE_RAW  * SECTORS_AT_ONCE];
		readaudio.buf = (uint8_t*)buf;
		if (ioctl(cdrom, CDROMREADAUDIO, &readaudio) < 0)
		{
			perror("ioctl");
			break;
		}
		SDL_PutAudioStreamData(stream, buf, CD_FRAMESIZE_RAW  * SECTORS_AT_ONCE);
		readaudio.addr.lba += SECTORS_AT_ONCE;
		while (SDL_GetAudioStreamQueued(stream) > CD_FRAMESIZE_RAW * MAX_SECTORS_BUFFERED)
			SDL_Delay(100);
	}

	close (cdrom);
	SDL_DestroyAudioStream(stream);
	return 0;
}