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ffmpeg / libavcodec / a52dec.c @ d0f4e4fb

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/*
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 * A52 decoder
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 * Copyright (c) 2001 Fabrice Bellard.
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file a52dec.c
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 * A52 decoder.
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 */
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#include "avcodec.h"
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#include "liba52/a52.h"
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#ifdef CONFIG_LIBA52BIN
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#include <dlfcn.h>
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static const char* liba52name = "liba52.so.0";
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#endif
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/**
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 * liba52 - Copyright (C) Aaron Holtzman
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 * released under the GPL license.
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 */
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typedef struct AC3DecodeState {
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    uint8_t inbuf[4096]; /* input buffer */
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    uint8_t *inbuf_ptr;
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    int frame_size;
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    int flags;
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    int channels;
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    a52_state_t* state;
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    sample_t* samples;
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    /*
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     * virtual method table
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     *
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     * using this function table so the liba52 doesn't
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     * have to be really linked together with ffmpeg
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     * and might be linked in runtime - this allows binary
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     * distribution of ffmpeg library which doens't depend
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     * on liba52 library - but if user has it installed
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     * it will be used - user might install such library
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     * separately
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     */
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    void* handle;
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    a52_state_t* (*a52_init)(uint32_t mm_accel);
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    sample_t* (*a52_samples)(a52_state_t * state);
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    int (*a52_syncinfo)(uint8_t * buf, int * flags,
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                          int * sample_rate, int * bit_rate);
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    int (*a52_frame)(a52_state_t * state, uint8_t * buf, int * flags,
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                       sample_t * level, sample_t bias);
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    void (*a52_dynrng)(a52_state_t * state,
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                         sample_t (* call) (sample_t, void *), void * data);
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    int (*a52_block)(a52_state_t * state);
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    void (*a52_free)(a52_state_t * state);
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} AC3DecodeState;
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#ifdef CONFIG_LIBA52BIN
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static void* dlsymm(void* handle, const char* symbol)
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{
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    void* f = dlsym(handle, symbol);
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    if (!f)
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        av_log( NULL, AV_LOG_ERROR, "A52 Decoder - function '%s' can't be resolved\n", symbol);
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    return f;
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}
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#endif
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static int a52_decode_init(AVCodecContext *avctx)
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{
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    AC3DecodeState *s = avctx->priv_data;
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#ifdef CONFIG_LIBA52BIN
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    s->handle = dlopen(liba52name, RTLD_LAZY);
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    if (!s->handle)
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    {
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        av_log( avctx, AV_LOG_ERROR, "A52 library %s could not be opened! \n%s\n", liba52name, dlerror());
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        return -1;
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    }
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    s->a52_init = (a52_state_t* (*)(uint32_t)) dlsymm(s->handle, "a52_init");
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    s->a52_samples = (sample_t* (*)(a52_state_t*)) dlsymm(s->handle, "a52_samples");
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    s->a52_syncinfo = (int (*)(uint8_t*, int*, int*, int*)) dlsymm(s->handle, "a52_syncinfo");
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    s->a52_frame = (int (*)(a52_state_t*, uint8_t*, int*, sample_t*, sample_t)) dlsymm(s->handle, "a52_frame");
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    s->a52_block = (int (*)(a52_state_t*)) dlsymm(s->handle, "a52_block");
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    s->a52_free = (void (*)(a52_state_t*)) dlsymm(s->handle, "a52_free");
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    if (!s->a52_init || !s->a52_samples || !s->a52_syncinfo
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        || !s->a52_frame || !s->a52_block || !s->a52_free)
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    {
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        dlclose(s->handle);
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        return -1;
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    }
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#else
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    /* static linked version */
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    s->handle = 0;
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    s->a52_init = a52_init;
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    s->a52_samples = a52_samples;
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    s->a52_syncinfo = a52_syncinfo;
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    s->a52_frame = a52_frame;
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    s->a52_block = a52_block;
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    s->a52_free = a52_free;
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#endif
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    s->state = s->a52_init(0); /* later use CPU flags */
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    s->samples = s->a52_samples(s->state);
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    s->inbuf_ptr = s->inbuf;
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    s->frame_size = 0;
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    return 0;
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}
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/**** the following two functions comes from a52dec */
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static inline int blah (int32_t i)
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{
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    if (i > 0x43c07fff)
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        return 32767;
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    else if (i < 0x43bf8000)
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        return -32768;
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    return i - 0x43c00000;
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}
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static inline void float_to_int (float * _f, int16_t * s16, int nchannels)
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{
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    int i, j, c;
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    int32_t * f = (int32_t *) _f;       // XXX assumes IEEE float format
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    j = 0;
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    nchannels *= 256;
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    for (i = 0; i < 256; i++) {
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        for (c = 0; c < nchannels; c += 256)
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            s16[j++] = blah (f[i + c]);
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    }
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}
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/**** end */
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#define HEADER_SIZE 7
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static int a52_decode_frame(AVCodecContext *avctx,
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                            void *data, int *data_size,
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                            uint8_t *buf, int buf_size)
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{
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    AC3DecodeState *s = avctx->priv_data;
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    uint8_t *buf_ptr;
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    int flags, i, len;
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    int sample_rate, bit_rate;
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    short *out_samples = data;
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    float level;
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    static const int ac3_channels[8] = {
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        2, 1, 2, 3, 3, 4, 4, 5
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    };
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    buf_ptr = buf;
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    while (buf_size > 0) {
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        len = s->inbuf_ptr - s->inbuf;
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        if (s->frame_size == 0) {
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            /* no header seen : find one. We need at least 7 bytes to parse it */
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            len = HEADER_SIZE - len;
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            if (len > buf_size)
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                len = buf_size;
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            memcpy(s->inbuf_ptr, buf_ptr, len);
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            buf_ptr += len;
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            s->inbuf_ptr += len;
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            buf_size -= len;
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            if ((s->inbuf_ptr - s->inbuf) == HEADER_SIZE) {
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                len = s->a52_syncinfo(s->inbuf, &s->flags, &sample_rate, &bit_rate);
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                if (len == 0) {
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                    /* no sync found : move by one byte (inefficient, but simple!) */
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                    memcpy(s->inbuf, s->inbuf + 1, HEADER_SIZE - 1);
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                    s->inbuf_ptr--;
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                } else {
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                    s->frame_size = len;
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                    /* update codec info */
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                    avctx->sample_rate = sample_rate;
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                    s->channels = ac3_channels[s->flags & 7];
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                    if (s->flags & A52_LFE)
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                        s->channels++;
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                    if (avctx->channels == 0)
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                        /* No specific number of channel requested */
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                        avctx->channels = s->channels;
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                    else if (s->channels < avctx->channels) {
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                        av_log(avctx, AV_LOG_ERROR, "ac3dec: AC3 Source channels are less than specified: output to %d channels.. (frmsize: %d)\n", s->channels, len);
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                        avctx->channels = s->channels;
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                    }
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                    avctx->bit_rate = bit_rate;
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                }
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            }
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        } else if (len < s->frame_size) {
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            len = s->frame_size - len;
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            if (len > buf_size)
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                len = buf_size;
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            memcpy(s->inbuf_ptr, buf_ptr, len);
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            buf_ptr += len;
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            s->inbuf_ptr += len;
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            buf_size -= len;
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        } else {
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            flags = s->flags;
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            if (avctx->channels == 1)
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                flags = A52_MONO;
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            else if (avctx->channels == 2)
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                flags = A52_STEREO;
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            else
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                flags |= A52_ADJUST_LEVEL;
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            level = 1;
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            if (s->a52_frame(s->state, s->inbuf, &flags, &level, 384)) {
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            fail:
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                av_log(avctx, AV_LOG_ERROR, "Error decoding frame\n");
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                s->inbuf_ptr = s->inbuf;
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                s->frame_size = 0;
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                continue;
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            }
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            for (i = 0; i < 6; i++) {
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                if (s->a52_block(s->state))
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                    goto fail;
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                float_to_int(s->samples, out_samples + i * 256 * avctx->channels, avctx->channels);
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            }
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            s->inbuf_ptr = s->inbuf;
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            s->frame_size = 0;
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            *data_size = 6 * avctx->channels * 256 * sizeof(int16_t);
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            break;
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        }
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    }
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    return buf_ptr - buf;
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}
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static int a52_decode_end(AVCodecContext *avctx)
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{
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    AC3DecodeState *s = avctx->priv_data;
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    s->a52_free(s->state);
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#ifdef CONFIG_LIBA52BIN
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    dlclose(s->handle);
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#endif
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    return 0;
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}
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AVCodec ac3_decoder = {
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    "ac3",
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    CODEC_TYPE_AUDIO,
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    CODEC_ID_AC3,
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    sizeof(AC3DecodeState),
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    a52_decode_init,
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    NULL,
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    a52_decode_end,
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    a52_decode_frame,
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};