www.pudn.com > ffmpeg_src2007.rar > a52dec.c
/* * A52 decoder * Copyright (c) 2001 Fabrice Bellard. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file a52dec.c * A52 decoder. */ #include "avcodec.h" #include "liba52/a52.h" #ifdef CONFIG_A52BIN #includestatic const char* liba52name = "liba52.so.0"; #endif /** * liba52 - Copyright (C) Aaron Holtzman * released under the GPL license. */ typedef struct AC3DecodeState { uint8_t inbuf[4096]; /* input buffer */ uint8_t *inbuf_ptr; int frame_size; int flags; int channels; a52_state_t* state; sample_t* samples; /* * virtual method table * * using this function table so the liba52 doesn't * have to be really linked together with ffmpeg * and might be linked in runtime - this allows binary * distribution of ffmpeg library which doens't depend * on liba52 library - but if user has it installed * it will be used - user might install such library * separately */ void* handle; a52_state_t* (*a52_init)(uint32_t mm_accel); sample_t* (*a52_samples)(a52_state_t * state); int (*a52_syncinfo)(uint8_t * buf, int * flags, int * sample_rate, int * bit_rate); int (*a52_frame)(a52_state_t * state, uint8_t * buf, int * flags, sample_t * level, sample_t bias); void (*a52_dynrng)(a52_state_t * state, sample_t (* call) (sample_t, void *), void * data); int (*a52_block)(a52_state_t * state); void (*a52_free)(a52_state_t * state); } AC3DecodeState; #ifdef CONFIG_A52BIN static void* dlsymm(void* handle, const char* symbol) { void* f = dlsym(handle, symbol); if (!f) av_log( NULL, AV_LOG_ERROR, "A52 Decoder - function '%s' can't be resolved\n", symbol); return f; } #endif static int a52_decode_init(AVCodecContext *avctx) { AC3DecodeState *s = avctx->priv_data; #ifdef CONFIG_A52BIN s->handle = dlopen(liba52name, RTLD_LAZY); if (!s->handle) { av_log( avctx, AV_LOG_ERROR, "A52 library %s could not be opened! \n%s\n", liba52name, dlerror()); return -1; } s->a52_init = (a52_state_t* (*)(uint32_t)) dlsymm(s->handle, "a52_init"); s->a52_samples = (sample_t* (*)(a52_state_t*)) dlsymm(s->handle, "a52_samples"); s->a52_syncinfo = (int (*)(uint8_t*, int*, int*, int*)) dlsymm(s->handle, "a52_syncinfo"); s->a52_frame = (int (*)(a52_state_t*, uint8_t*, int*, sample_t*, sample_t)) dlsymm(s->handle, "a52_frame"); s->a52_block = (int (*)(a52_state_t*)) dlsymm(s->handle, "a52_block"); s->a52_free = (void (*)(a52_state_t*)) dlsymm(s->handle, "a52_free"); if (!s->a52_init || !s->a52_samples || !s->a52_syncinfo || !s->a52_frame || !s->a52_block || !s->a52_free) { dlclose(s->handle); return -1; } #else /* static linked version */ s->handle = 0; s->a52_init = a52_init; s->a52_samples = a52_samples; s->a52_syncinfo = a52_syncinfo; s->a52_frame = a52_frame; s->a52_block = a52_block; s->a52_free = a52_free; #endif s->state = s->a52_init(0); /* later use CPU flags */ s->samples = s->a52_samples(s->state); s->inbuf_ptr = s->inbuf; s->frame_size = 0; return 0; } /**** the following two functions comes from a52dec */ static inline int blah (int32_t i) { if (i > 0x43c07fff) return 32767; else if (i < 0x43bf8000) return -32768; return i - 0x43c00000; } static inline void float_to_int (float * _f, int16_t * s16, int nchannels) { int i, j, c; int32_t * f = (int32_t *) _f; // XXX assumes IEEE float format j = 0; nchannels *= 256; for (i = 0; i < 256; i++) { for (c = 0; c < nchannels; c += 256) s16[j++] = blah (f[i + c]); } } /**** end */ #define HEADER_SIZE 7 static int a52_decode_frame(AVCodecContext *avctx, void *data, int *data_size, uint8_t *buf, int buf_size) { AC3DecodeState *s = avctx->priv_data; uint8_t *buf_ptr; int flags, i, len; int sample_rate, bit_rate; short *out_samples = data; float level; static const int ac3_channels[8] = { 2, 1, 2, 3, 3, 4, 4, 5 }; buf_ptr = buf; while (buf_size > 0) { len = s->inbuf_ptr - s->inbuf; if (s->frame_size == 0) { /* no header seen : find one. We need at least 7 bytes to parse it */ len = HEADER_SIZE - len; if (len > buf_size) len = buf_size; memcpy(s->inbuf_ptr, buf_ptr, len); buf_ptr += len; s->inbuf_ptr += len; buf_size -= len; if ((s->inbuf_ptr - s->inbuf) == HEADER_SIZE) { len = s->a52_syncinfo(s->inbuf, &s->flags, &sample_rate, &bit_rate); if (len == 0) { /* no sync found : move by one byte (inefficient, but simple!) */ memcpy(s->inbuf, s->inbuf + 1, HEADER_SIZE - 1); s->inbuf_ptr--; } else { s->frame_size = len; /* update codec info */ avctx->sample_rate = sample_rate; s->channels = ac3_channels[s->flags & 7]; if (s->flags & A52_LFE) s->channels++; if (avctx->channels == 0) /* No specific number of channel requested */ avctx->channels = s->channels; else if (s->channels < avctx->channels) { av_log(avctx, AV_LOG_ERROR, "ac3dec: AC3 Source channels are less than specified: output to %d channels.. (frmsize: %d)\n", s->channels, len); avctx->channels = s->channels; } avctx->bit_rate = bit_rate; } } } else if (len < s->frame_size) { len = s->frame_size - len; if (len > buf_size) len = buf_size; memcpy(s->inbuf_ptr, buf_ptr, len); buf_ptr += len; s->inbuf_ptr += len; buf_size -= len; } else { flags = s->flags; if (avctx->channels == 1) flags = A52_MONO; else if (avctx->channels == 2) flags = A52_STEREO; else flags |= A52_ADJUST_LEVEL; level = 1; if (s->a52_frame(s->state, s->inbuf, &flags, &level, 384)) { fail: s->inbuf_ptr = s->inbuf; s->frame_size = 0; continue; } for (i = 0; i < 6; i++) { if (s->a52_block(s->state)) goto fail; float_to_int(s->samples, out_samples + i * 256 * avctx->channels, avctx->channels); } s->inbuf_ptr = s->inbuf; s->frame_size = 0; *data_size = 6 * avctx->channels * 256 * sizeof(int16_t); break; } } return buf_ptr - buf; } static int a52_decode_end(AVCodecContext *avctx) { AC3DecodeState *s = avctx->priv_data; s->a52_free(s->state); #ifdef CONFIG_A52BIN dlclose(s->handle); #endif return 0; } AVCodec ac3_decoder = { "ac3", CODEC_TYPE_AUDIO, CODEC_ID_AC3, sizeof(AC3DecodeState), a52_decode_init, NULL, a52_decode_end, a52_decode_frame, };