FreeCalypso > hg > gsm-codec-lib
view libtest/wavwriter.c @ 242:f081a6850fb5
libgsmfrp: new refined implementation
The previous implementation exhibited the following defects,
which are now fixed:
1) The last received valid SID was cached forever for the purpose of
handling future invalid SIDs - we could have received some valid
SID ages ago, then lots of speech or NO_DATA, and if we then get
an invalid SID, we would resurrect the last valid SID from ancient
history - a bad design. In our new design, we handle invalid SID
based on the current state, much like BFI.
2) GSM 06.11 spec says clearly that after the second lost SID
(received BFI=1 && TAF=1 in CN state) we need to gradually decrease
the output level, rather than jump directly to emitting silence
frames - we previously failed to implement such logic.
3) Per GSM 06.12 section 5.2, Xmaxc should be the same in all 4 subframes
in a SID frame. What should we do if we receive an otherwise valid
SID frame with different Xmaxc? Our previous approach would
replicate this Xmaxc oddity in every subsequent generated CN frame,
which is rather bad. In our new design, the very first CN frame
(which can be seen as a transformation of the SID frame itself)
retains the original 4 distinct Xmaxc, but all subsequent CN frames
are based on the Xmaxc from the last subframe of the most recent SID.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Tue, 09 May 2023 05:16:31 +0000 |
parents | 634df6435e16 |
children |
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/* ------------------------------------------------------------------ * Copyright (C) 2009 Martin Storsjo * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either * express or implied. * See the License for the specific language governing permissions * and limitations under the License. * ------------------------------------------------------------------- */ #include "wavwriter.h" #include <stdio.h> #include <string.h> #include <stdlib.h> #include <stdint.h> struct wav_writer { FILE *wav; int data_length; int sample_rate; int bits_per_sample; int channels; }; static void write_string(struct wav_writer* ww, const char *str) { fputc(str[0], ww->wav); fputc(str[1], ww->wav); fputc(str[2], ww->wav); fputc(str[3], ww->wav); } static void write_int32(struct wav_writer* ww, int value) { fputc((value >> 0) & 0xff, ww->wav); fputc((value >> 8) & 0xff, ww->wav); fputc((value >> 16) & 0xff, ww->wav); fputc((value >> 24) & 0xff, ww->wav); } static void write_int16(struct wav_writer* ww, int value) { fputc((value >> 0) & 0xff, ww->wav); fputc((value >> 8) & 0xff, ww->wav); } static void write_header(struct wav_writer* ww, int length) { int bytes_per_frame, bytes_per_sec; write_string(ww, "RIFF"); write_int32(ww, 4 + 8 + 16 + 8 + length); write_string(ww, "WAVE"); write_string(ww, "fmt "); write_int32(ww, 16); bytes_per_frame = ww->bits_per_sample/8*ww->channels; bytes_per_sec = bytes_per_frame*ww->sample_rate; write_int16(ww, 1); // Format write_int16(ww, ww->channels); // Channels write_int32(ww, ww->sample_rate); // Samplerate write_int32(ww, bytes_per_sec); // Bytes per sec write_int16(ww, bytes_per_frame); // Bytes per frame write_int16(ww, ww->bits_per_sample); // Bits per sample write_string(ww, "data"); write_int32(ww, length); } void* wav_write_open(const char *filename, int sample_rate, int bits_per_sample, int channels) { struct wav_writer* ww = (struct wav_writer*) malloc(sizeof(*ww)); memset(ww, 0, sizeof(*ww)); ww->wav = fopen(filename, "wb"); if (ww->wav == NULL) { free(ww); return NULL; } ww->data_length = 0; ww->sample_rate = sample_rate; ww->bits_per_sample = bits_per_sample; ww->channels = channels; write_header(ww, ww->data_length); return ww; } void wav_write_close(void* obj) { struct wav_writer* ww = (struct wav_writer*) obj; if (ww->wav == NULL) { free(ww); return; } fseek(ww->wav, 0, SEEK_SET); write_header(ww, ww->data_length); fclose(ww->wav); free(ww); } void wav_write_data(void* obj, const unsigned char* data, int length) { struct wav_writer* ww = (struct wav_writer*) obj; if (ww->wav == NULL) return; fwrite(data, length, 1, ww->wav); ww->data_length += length; }