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ffmpeg / libavcodec / rl2.c @ 72415b2a

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/*
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 * RL2 Video Decoder
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 * Copyright (C) 2008 Sascha Sommer (saschasommer@freenet.de)
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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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 * RL2 Video Decoder
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 * @file libavcodec/rl2.c
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 * @author Sascha Sommer (saschasommer@freenet.de)
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 * For more information about the RL2 format, visit:
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 *   http://wiki.multimedia.cx/index.php?title=RL2
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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "libavutil/intreadwrite.h"
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#include "avcodec.h"
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#define EXTRADATA1_SIZE (6 + 256 * 3) ///< video base, clr count, palette
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typedef struct Rl2Context {
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    AVCodecContext *avctx;
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    AVFrame frame;
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    unsigned short video_base; ///< initial drawing offset
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    unsigned int clr_count;    ///< number of used colors (currently unused)
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    unsigned char* back_frame; ///< background frame
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    unsigned int palette[AVPALETTE_COUNT];
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} Rl2Context;
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/**
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 * Run Length Decode a single 320x200 frame
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 * @param s rl2 context
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 * @param buf input buffer
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 * @param size input buffer size
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 * @param out ouput buffer
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 * @param stride stride of the output buffer
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 * @param video_base offset of the rle data inside the frame
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 */
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static void rl2_rle_decode(Rl2Context *s,const unsigned char* in,int size,
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                               unsigned char* out,int stride,int video_base){
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    int base_x = video_base % s->avctx->width;
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    int base_y = video_base / s->avctx->width;
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    int stride_adj = stride - s->avctx->width;
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    int i;
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    const unsigned char* back_frame = s->back_frame;
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    const unsigned char* in_end = in + size;
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    const unsigned char* out_end = out + stride * s->avctx->height;
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    unsigned char* line_end = out + s->avctx->width;
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    /** copy start of the background frame */
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    for(i=0;i<=base_y;i++){
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        if(s->back_frame)
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            memcpy(out,back_frame,s->avctx->width);
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        out += stride;
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        back_frame += s->avctx->width;
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    }
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    back_frame += base_x - s->avctx->width;
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    line_end = out - stride_adj;
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    out += base_x - stride;
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    /** decode the variable part of the frame */
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    while(in < in_end){
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        unsigned char val = *in++;
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        int len = 1;
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        if(val >= 0x80){
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            if(in >= in_end)
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                break;
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            len = *in++;
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            if(!len)
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                break;
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        }
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        if(len >= out_end - out)
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            break;
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        if(s->back_frame)
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            val |= 0x80;
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        else
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            val &= ~0x80;
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        while(len--){
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            *out++ = (val == 0x80)? *back_frame:val;
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            back_frame++;
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            if(out == line_end){
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                 out += stride_adj;
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                 line_end += stride;
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                 if(len >= out_end - out)
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                     break;
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            }
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        }
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    }
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    /** copy the rest from the background frame */
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    if(s->back_frame){
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        while(out < out_end){
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            memcpy(out, back_frame, line_end - out);
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            back_frame += line_end - out;
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            out = line_end + stride_adj;
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            line_end += stride;
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        }
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    }
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}
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/**
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 * Initialize the decoder
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 * @param avctx decoder context
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 * @return 0 success, -1 on error
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 */
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static av_cold int rl2_decode_init(AVCodecContext *avctx)
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{
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    Rl2Context *s = avctx->priv_data;
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    int back_size;
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    int i;
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    s->avctx = avctx;
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    avctx->pix_fmt = PIX_FMT_PAL8;
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    /** parse extra data */
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    if(!avctx->extradata || avctx->extradata_size < EXTRADATA1_SIZE){
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        av_log(avctx, AV_LOG_ERROR, "invalid extradata size\n");
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        return -1;
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    }
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    /** get frame_offset */
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    s->video_base = AV_RL16(&avctx->extradata[0]);
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    s->clr_count = AV_RL32(&avctx->extradata[2]);
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    if(s->video_base >= avctx->width * avctx->height){
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        av_log(avctx, AV_LOG_ERROR, "invalid video_base\n");
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        return -1;
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    }
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    /** initialize palette */
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    for(i=0;i<AVPALETTE_COUNT;i++)
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        s->palette[i] = AV_RB24(&avctx->extradata[6 + i * 3]);
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    /** decode background frame if present */
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    back_size = avctx->extradata_size - EXTRADATA1_SIZE;
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    if(back_size > 0){
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        unsigned char* back_frame = av_mallocz(avctx->width*avctx->height);
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        if(!back_frame)
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            return -1;
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        rl2_rle_decode(s,avctx->extradata + EXTRADATA1_SIZE,back_size,
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                           back_frame,avctx->width,0);
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        s->back_frame = back_frame;
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    }
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    return 0;
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}
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/**
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 * Decode a single frame
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 * @param avctx decoder context
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 * @param data decoded frame
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 * @param data_size size of the decoded frame
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 * @param buf input buffer
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 * @param buf_size input buffer size
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 * @return 0 success, -1 on error
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 */
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static int rl2_decode_frame(AVCodecContext *avctx,
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                              void *data, int *data_size,
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                              AVPacket *avpkt)
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{
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    const uint8_t *buf = avpkt->data;
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    int buf_size = avpkt->size;
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    Rl2Context *s = avctx->priv_data;
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    if(s->frame.data[0])
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        avctx->release_buffer(avctx, &s->frame);
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    /** get buffer */
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    s->frame.reference= 0;
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    if(avctx->get_buffer(avctx, &s->frame)) {
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        av_log(s->avctx, AV_LOG_ERROR, "get_buffer() failed\n");
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        return -1;
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    }
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    /** run length decode */
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    rl2_rle_decode(s,buf,buf_size,s->frame.data[0],s->frame.linesize[0],s->video_base);
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    /** make the palette available on the way out */
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    memcpy(s->frame.data[1], s->palette, AVPALETTE_SIZE);
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    *data_size = sizeof(AVFrame);
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    *(AVFrame*)data = s->frame;
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    /** report that the buffer was completely consumed */
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    return buf_size;
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}
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/**
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 * Uninit decoder
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 * @param avctx decoder context
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 * @return 0 success, -1 on error
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 */
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static av_cold int rl2_decode_end(AVCodecContext *avctx)
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{
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    Rl2Context *s = avctx->priv_data;
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    if(s->frame.data[0])
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        avctx->release_buffer(avctx, &s->frame);
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    av_free(s->back_frame);
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    return 0;
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}
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AVCodec rl2_decoder = {
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    "rl2",
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    AVMEDIA_TYPE_VIDEO,
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    CODEC_ID_RL2,
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    sizeof(Rl2Context),
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    rl2_decode_init,
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    NULL,
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    rl2_decode_end,
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    rl2_decode_frame,
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    CODEC_CAP_DR1,
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    .long_name = NULL_IF_CONFIG_SMALL("RL2 video"),
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};
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