X-Git-Url: https://git.sesse.net/?p=c64tapwav;a=blobdiff_plain;f=decode.cpp;h=ec95faad5c960ad19fe5f137bded32c2faa2f7fb;hp=fdc1347e0e124a7297ab4c6ef4a71e644c58f0fd;hb=4146b98dc2a5bad67c67fe817cb2eb060eac19ea;hpb=2d875bfb4e11cea397aeb88d9781d8a36079c9a1 diff --git a/decode.cpp b/decode.cpp index fdc1347..ec95faa 100644 --- a/decode.cpp +++ b/decode.cpp @@ -1,34 +1,26 @@ #include #include #include -#include #include #include #include #include +#include "audioreader.h" #include "interpolate.h" +#include "tap.h" #define BUFSIZE 4096 #define HYSTERESIS_LIMIT 3000 -#define SAMPLE_RATE 44100 #define C64_FREQUENCY 985248 -#define TAP_RESOLUTION 8 #define SYNC_PULSE_START 1000 -#define SYNC_PULSE_END 15000 +#define SYNC_PULSE_END 20000 #define SYNC_PULSE_LENGTH 378.0 #define SYNC_TEST_TOLERANCE 1.10 -struct tap_header { - char identifier[12]; - char version; - char reserved[3]; - unsigned int data_len; -}; - // between [x,x+1] -double find_zerocrossing(const std::vector &pcm, int x) +double find_zerocrossing(const std::vector &pcm, int x) { if (pcm[x] == 0) { return x; @@ -42,7 +34,7 @@ double find_zerocrossing(const std::vector &pcm, int x) double upper = x; double lower = x + 1; - while (upper - lower > 1e-6) { + while (lower - upper > 1e-3) { double mid = 0.5f * (upper + lower); if (lanczos_interpolate(pcm, mid) > 0) { upper = mid; @@ -58,18 +50,99 @@ struct pulse { double time; // in seconds from start double len; // in seconds }; + +// Calibrate on the first ~25k pulses (skip a few, just to be sure). +double calibrate(const std::vector &pulses) { + if (pulses.size() < SYNC_PULSE_END) { + fprintf(stderr, "Too few pulses, not calibrating!\n"); + return 1.0; + } + + int sync_pulse_end = -1; + double sync_pulse_stddev = -1.0; + + // Compute the standard deviation (to check for uneven speeds). + // If it suddenly skyrockets, we assume that sync ended earlier + // than we thought (it should be 25000 cycles), and that we should + // calibrate on fewer cycles. + for (int try_end : { 2000, 4000, 5000, 7500, 10000, 15000, SYNC_PULSE_END }) { + double sum2 = 0.0; + for (int i = SYNC_PULSE_START; i < try_end; ++i) { + double cycles = pulses[i].len * C64_FREQUENCY; + sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH); + } + double stddev = sqrt(sum2 / (try_end - SYNC_PULSE_START - 1)); + if (sync_pulse_end != -1 && stddev > 5.0 && stddev / sync_pulse_stddev > 1.3) { + fprintf(stderr, "Stopping at %d sync pulses because standard deviation would be too big (%.2f cycles); shorter-than-usual trailer?\n", + sync_pulse_end, stddev); + break; + } + sync_pulse_end = try_end; + sync_pulse_stddev = stddev; + } + fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n", + sync_pulse_stddev); + + double sum = 0.0; + for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) { + sum += pulses[i].len; + } + double mean_length = C64_FREQUENCY * sum / (sync_pulse_end - SYNC_PULSE_START); + double calibration_factor = SYNC_PULSE_LENGTH / mean_length; + fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n", + mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0)); + + // Check for pulses outside +/- 10% (sign of misdetection). + for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) { + double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY; + if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) { + fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n", + pulses[i].time, cycles); + } + } + + return calibration_factor; +} + +void output_tap(const std::vector& pulses, double calibration_factor) +{ + std::vector tap_data; + for (unsigned i = 0; i < pulses.size(); ++i) { + double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY; + int len = lrintf(cycles / TAP_RESOLUTION); + if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) { + fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n", + pulses[i].time, cycles); + } + if (len <= 255) { + tap_data.push_back(len); + } else { + int overflow_len = lrintf(cycles); + tap_data.push_back(0); + tap_data.push_back(overflow_len & 0xff); + tap_data.push_back((overflow_len >> 8) & 0xff); + tap_data.push_back(overflow_len >> 16); + } + } + + tap_header hdr; + memcpy(hdr.identifier, "C64-TAPE-RAW", 12); + hdr.version = 1; + hdr.reserved[0] = hdr.reserved[1] = hdr.reserved[2] = 0; + hdr.data_len = tap_data.size(); + + fwrite(&hdr, sizeof(hdr), 1, stdout); + fwrite(tap_data.data(), tap_data.size(), 1, stdout); +} int main(int argc, char **argv) { - std::vector pcm; - - while (!feof(stdin)) { - short buf[BUFSIZE]; - ssize_t ret = fread(buf, 2, BUFSIZE, stdin); - if (ret >= 0) { - pcm.insert(pcm.end(), buf, buf + ret); - } - } + make_lanczos_weight_table(); + std::vector pcm; + int sample_rate; + if (!read_audio_file(argv[1], &pcm, &sample_rate)) { + exit(1); + } #if 0 for (int i = 0; i < LEN; ++i) { @@ -107,14 +180,14 @@ int main(int argc, char **argv) if (!true_pulse) { #if 0 fprintf(stderr, "Ignored down-flank at %.6f seconds due to hysteresis (%d < %d).\n", - double(i) / SAMPLE_RATE, -min_level_after, HYSTERESIS_LIMIT); + double(i) / sample_rate, -min_level_after, HYSTERESIS_LIMIT); #endif i = j; continue; } // down-flank! - double t = find_zerocrossing(pcm, i - 1) * (1.0 / SAMPLE_RATE); + double t = find_zerocrossing(pcm, i - 1) * (1.0 / sample_rate); if (last_downflank > 0) { pulse p; p.time = t; @@ -126,84 +199,15 @@ int main(int argc, char **argv) last_bit = bit; } - // Calibrate on the first ~25k pulses (skip a few, just to be sure). - double calibration_factor = 1.0f; - if (pulses.size() < SYNC_PULSE_END) { - fprintf(stderr, "Too few pulses, not calibrating!\n"); - } else { - double sum = 0.0; - for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) { - sum += pulses[i].len; - } - double mean_length = C64_FREQUENCY * sum / (SYNC_PULSE_END - SYNC_PULSE_START); - calibration_factor = SYNC_PULSE_LENGTH / mean_length; - fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n", - mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0)); - - // Check for pulses outside +/- 10% (sign of misdetection). - for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) { - double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY; - if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) { - fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n", - pulses[i].time, cycles); - } - } - - // Compute the standard deviation (to check for uneven speeds). - double sum2 = 0.0; - for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) { - double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY; - sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH); - } - double stddev = sqrt(sum2 / (SYNC_PULSE_END - SYNC_PULSE_START - 1)); - fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n", - stddev); - } + double calibration_factor = calibrate(pulses); FILE *fp = fopen("cycles.plot", "w"); std::vector tap_data; for (unsigned i = 0; i < pulses.size(); ++i) { double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY; fprintf(fp, "%f %f\n", pulses[i].time, cycles); - int len = lrintf(cycles / TAP_RESOLUTION); - if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) { - fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n", - pulses[i].time, cycles); - } - if (len <= 255) { - tap_data.push_back(len); - } else { - int overflow_len = lrintf(cycles); - tap_data.push_back(0); - tap_data.push_back(overflow_len & 0xff); - tap_data.push_back((overflow_len >> 8) & 0xff); - tap_data.push_back(overflow_len >> 16); - } } fclose(fp); - tap_header hdr; - memcpy(hdr.identifier, "C64-TAPE-RAW", 12); - hdr.version = 1; - hdr.reserved[0] = hdr.reserved[1] = hdr.reserved[2] = 0; - hdr.data_len = tap_data.size(); - - fwrite(&hdr, sizeof(hdr), 1, stdout); - fwrite(tap_data.data(), tap_data.size(), 1, stdout); - - // Output a debug raw file with pulse detection points. - fp = fopen("debug.raw", "wb"); - short one = 32767; - short zero = 0; - unsigned pulsenum = 0; - for (unsigned i = 0; i < pcm.size(); ++i) { - unsigned next_pulse = (pulsenum >= pulses.size()) ? INT_MAX : int(pulses[pulsenum].time * SAMPLE_RATE); - if (i >= next_pulse) { - fwrite(&one, sizeof(one), 1, fp); - ++pulsenum; - } else { - fwrite(&zero, sizeof(zero), 1, fp); - } - } - fclose(fp); + output_tap(pulses, calibration_factor); }