diff options
Diffstat (limited to 'contrib/ffmpeg/libavcodec/ac3dec.c')
| -rw-r--r-- | contrib/ffmpeg/libavcodec/ac3dec.c | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/contrib/ffmpeg/libavcodec/ac3dec.c b/contrib/ffmpeg/libavcodec/ac3dec.c new file mode 100644 index 000000000..b6bebfb59 --- /dev/null +++ b/contrib/ffmpeg/libavcodec/ac3dec.c @@ -0,0 +1,184 @@ +/* + * AC3 decoder + * Copyright (c) 2001 Fabrice Bellard. + * + * This file is part of FFmpeg. + * + * FFmpeg 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 2.1 of the License, or (at your option) any later version. + * + * FFmpeg 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 FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/** + * @file ac3dec.c + * AC3 decoder. + */ + +//#define DEBUG + +#include "avcodec.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_t inbuf[4096]; /* input buffer */ + uint8_t *inbuf_ptr; + int frame_size; + int flags; + int channels; + 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_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 ac3_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 = 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; + s->channels = ac3_channels[s->flags & 7]; + if (s->flags & AC3_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_INFO, "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 = AC3_MONO; + else if (avctx->channels == 2) + flags = AC3_STEREO; + else + 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; + float_to_int (*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 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, +}; |