diff options
Diffstat (limited to 'libavcodec/ac3dec.c')
| -rw-r--r-- | libavcodec/ac3dec.c | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c new file mode 100644 index 0000000000..7332a11d8e --- /dev/null +++ b/libavcodec/ac3dec.c @@ -0,0 +1,189 @@ +/* + * AC3 decoder + * Copyright (c) 2001 Gerard Lantau. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include "avcodec.h" + +#include <inttypes.h> +#include "libac3/ac3.h" + +/* currently, I use libac3 which is Copyright (C) Aaron Holtzman and + released under the GPL license. I may reimplement it someday... */ +typedef struct AC3DecodeState { + UINT8 inbuf[4096]; /* input buffer */ + UINT8 *inbuf_ptr; + int frame_size; + int flags; + ac3_state_t state; +} AC3DecodeState; + +static int ac3_decode_init(AVCodecContext *avctx) +{ + AC3DecodeState *s = avctx->priv_data; + + ac3_init (); + s->inbuf_ptr = s->inbuf; + s->frame_size = 0; + return 0; +} + +stream_samples_t samples; + +/**** the following two functions comes from ac3dec */ +static inline int blah (int32_t i) +{ + if (i > 0x43c07fff) + return 32767; + else if (i < 0x43bf8000) + return -32768; + else + return i - 0x43c00000; +} + +static inline void float_to_int (float * _f, INT16 * s16) +{ + int i; + int32_t * f = (int32_t *) _f; // XXX assumes IEEE float format + + for (i = 0; i < 256; i++) { + s16[2*i] = blah (f[i]); + s16[2*i+1] = blah (f[i+256]); + } +} + +static inline void float_to_int_mono (float * _f, INT16 * s16) +{ + int i; + int32_t * f = (int32_t *) _f; // XXX assumes IEEE float format + + for (i = 0; i < 256; i++) { + s16[i] = blah (f[i]); + } +} + +/**** end */ + +#define HEADER_SIZE 7 + +static int ac3_decode_frame(AVCodecContext *avctx, + void *data, int *data_size, + UINT8 *buf, int buf_size) +{ + AC3DecodeState *s = avctx->priv_data; + UINT8 *buf_ptr; + int flags, i, len; + int sample_rate, bit_rate; + short *out_samples = data; + float level; + + *data_size = 0; + 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 = ac3_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; + if ((s->flags & AC3_CHANNEL_MASK) == AC3_MONO) + avctx->channels = 1; + else + avctx->channels = 2; + 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 { + if (avctx->channels == 1) + flags = AC3_MONO; + else + flags = AC3_STEREO; + + flags |= AC3_ADJUST_LEVEL; + level = 1; + if (ac3_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 (ac3_block (&s->state)) + goto fail; + if (avctx->channels == 1) + float_to_int_mono (*samples, out_samples + i * 256); + else + float_to_int (*samples, out_samples + i * 512); + } + s->inbuf_ptr = s->inbuf; + s->frame_size = 0; + *data_size = 6 * avctx->channels * 256 * sizeof(INT16); + break; + } + } + return buf_ptr - buf; +} + +static int ac3_decode_end(AVCodecContext *s) +{ + return 0; +} + +AVCodec ac3_decoder = { + "ac3", + CODEC_TYPE_AUDIO, + CODEC_ID_AC3, + sizeof(AC3DecodeState), + ac3_decode_init, + NULL, + ac3_decode_end, + ac3_decode_frame, +}; + +/* register codecs which could clash with mplayer symbols */ +/* XXX: rename all symbols to avoid clashed */ +void avcodec_register_more(void) +{ + register_avcodec(&mp3_decoder); + register_avcodec(&ac3_decoder); +} + |