161 lines
4.1 KiB
C
161 lines
4.1 KiB
C
#include "coding.h"
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#ifdef VGM_USE_G7221
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#include "g7221_decoder_lib.h"
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#define G7221_MAX_FRAME_SIZE 0x78 /* 960/8 */
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#define G7221_MAX_FRAME_SAMPLES 640 /* 32000/50 */
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struct g7221_codec_data {
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int channels;
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int frame_size;
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struct g7221_channel_data {
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sample_t buffer[G7221_MAX_FRAME_SAMPLES];
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g7221_handle* handle;
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} *ch;
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};
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g7221_codec_data* init_g7221(int channels, int frame_size) {
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int i;
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g7221_codec_data* data = NULL;
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if (frame_size > G7221_MAX_FRAME_SIZE)
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goto fail;
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data = calloc(1, sizeof(g7221_codec_data));
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if (!data) goto fail;
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data->channels = channels;
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data->frame_size = frame_size;
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data->ch = calloc(channels, sizeof(struct g7221_channel_data));
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if (!data->ch) goto fail;
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for (i = 0; i < data->channels; i++) {
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data->ch[i].handle = g7221_init(frame_size);
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if (!data->ch[i].handle) goto fail;
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}
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return data;
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fail:
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free_g7221(data);
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return NULL;
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}
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void decode_g7221(VGMSTREAM* vgmstream, sample_t* outbuf, int channelspacing, int32_t samples_to_do, int channel) {
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VGMSTREAMCHANNEL* ch = &vgmstream->ch[channel];
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g7221_codec_data* data = vgmstream->codec_data;
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struct g7221_channel_data* ch_data = &data->ch[channel];
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int i;
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if (0 == vgmstream->samples_into_block) {
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uint8_t buf[G7221_MAX_FRAME_SIZE];
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size_t bytes;
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size_t read = data->frame_size;
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bytes = read_streamfile(buf, ch->offset, read, ch->streamfile);
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if (bytes != read) {
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//g7221_decode_empty(ch_data->handle, ch_data->buffer);
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memset(ch_data->buffer, 0, sizeof(ch_data->buffer));
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VGM_LOG("S14: EOF read\n");
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}
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else {
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g7221_decode_frame(ch_data->handle, buf, ch_data->buffer);
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}
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}
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for (i = 0; i < samples_to_do; i++) {
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outbuf[i*channelspacing] = ch_data->buffer[vgmstream->samples_into_block+i];
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}
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}
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void reset_g7221(g7221_codec_data* data) {
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int i;
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if (!data) return;
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for (i = 0; i < data->channels; i++) {
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g7221_reset(data->ch[i].handle);
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}
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}
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void free_g7221(g7221_codec_data* data) {
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int i;
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if (!data) return;
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for (i = 0; i < data->channels; i++) {
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g7221_free(data->ch[i].handle);
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}
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free(data->ch);
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free(data);
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}
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void set_key_g7221(g7221_codec_data* data, const uint8_t* key) {
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int i;
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if (!data) return;
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for (i = 0; i < data->channels; i++) {
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g7221_set_key(data->ch[i].handle, key);
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}
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}
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/* just in case but very few should be enough */
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#define S14_KEY_MIN_TEST_FRAMES 3
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#define S14_KEY_MAX_TEST_FRAMES 5
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/* Test a number of frames to check if current key decrypts correctly.
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* Returns score: <0: error/wrong, 0: unknown/silent, >0: good (closer to 1 is better). */
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int test_key_g7221(g7221_codec_data* data, off_t start, STREAMFILE* sf) {
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size_t test_frames = 0, current_frame = 0;
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int total_score = 0;
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int max_frames = (get_streamfile_size(sf) - start) / data->frame_size;
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int cur_ch = 0;
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/* assumes key was set before this call */
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while (test_frames < S14_KEY_MAX_TEST_FRAMES && current_frame < max_frames) {
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int score, res;
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size_t bytes;
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uint8_t buf[G7221_MAX_FRAME_SIZE];
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bytes = read_streamfile(buf, start, data->frame_size, sf);
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if (bytes != data->frame_size) {
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total_score = -1;
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break;
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}
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res = g7221_decode_frame(data->ch[cur_ch].handle, buf, data->ch[cur_ch].buffer);
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if (res < 0) {
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total_score = -1;
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break;
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}
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/* alternate channels (decode may affect scores otherwise) */
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cur_ch = (cur_ch + 1) % data->channels;
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/* good key if it decodes without error, encryption is easily detectable */
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score = 1;
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test_frames++;
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total_score += score;
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start += data->frame_size;
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}
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/* signal best possible score (many perfect frames and few blank frames) */
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if (test_frames > S14_KEY_MIN_TEST_FRAMES && total_score > 0 && total_score <= test_frames) {
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total_score = 1;
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}
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/* clean up decoders */
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reset_g7221(data);
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return total_score;
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}
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#endif
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