graphparser.c 8.37 KB
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/*
 * filter graph parser
 * copyright (c) 2008 Vitor Sessak
 * copyright (c) 2007 Bobby Bingham
 *
 * 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
 */

#include <ctype.h>
#include <string.h>

#include "avfilter.h"
#include "avfiltergraph.h"

/**
 * For use in av_log
 */
static const char *log_name(void *p)
{
    return "Filter parser";
}

static const AVClass filter_parser_class = {
    "Filter parser",
    log_name
};

static const AVClass *log_ctx = &filter_parser_class;

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static AVFilterContext *create_filter(AVFilterGraph *ctx, int index,
                                      char *name, char *args)
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{
    AVFilterContext *filt;

    AVFilter *filterdef;
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    char inst_name[30];
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    snprintf(inst_name, sizeof(inst_name), "Parsed filter %d", index);
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    if(!(filterdef = avfilter_get_by_name(name))) {
        av_log(&log_ctx, AV_LOG_ERROR,
               "no such filter: '%s'\n", name);
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        return NULL;
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    }

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    if(!(filt = avfilter_open(filterdef, inst_name))) {
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        av_log(&log_ctx, AV_LOG_ERROR,
               "error creating filter '%s'\n", name);
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        return NULL;
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    }
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    if(avfilter_graph_add_filter(ctx, filt) < 0)
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        return NULL;
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    if(avfilter_init_filter(filt, args, NULL)) {
        av_log(&log_ctx, AV_LOG_ERROR,
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               "error initializing filter '%s' with args '%s'\n", name, args);
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        return NULL;
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    }

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    return filt;
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}

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static int link_filter(AVFilterContext *src, int srcpad,
                       AVFilterContext *dst, int dstpad)
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{
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    if(avfilter_link(src, srcpad, dst, dstpad)) {
        av_log(&log_ctx, AV_LOG_ERROR,
               "cannot create the link %s:%d -> %s:%d\n",
               src->filter->name, srcpad, dst->filter->name, dstpad);
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        return -1;
    }

    return 0;
}

static void consume_whitespace(const char **buf)
{
    *buf += strspn(*buf, " \n\t");
}

/**
 * Consumes a string from *buf.
 * @return a copy of the consumed string, which should be free'd after use
 */
static char *consume_string(const char **buf)
{
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    char *out = av_malloc(strlen(*buf) + 1);
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    const char *in = *buf;
    char *ret = out;
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    consume_whitespace(buf);

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    do{
        char c = *in++;
        switch (c) {
        case '\\':
            *out++= *in++;
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            break;
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        case '\'':
            while(*in && *in != '\'')
                *out++= *in++;
            if(*in) in++;
            break;
        case 0:
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        case ']':
        case '[':
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        case '=':
        case ',':
            *out++= 0;
            break;
        default:
            *out++= c;
        }
    } while(out[-1]);
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    *buf = in-1;
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    return ret;
}

/**
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 * Parse "[linkname]"
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 * @arg name a pointer (that need to be free'd after use) to the name between
 *           parenthesis
 */
static void parse_link_name(const char **buf, char **name)
{
    (*buf)++;

    *name = consume_string(buf);

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    if(!*name[0])
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        goto fail;

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    if(*(*buf)++ != ']')
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        goto fail;

    return;
 fail:
    av_freep(name);
    av_log(&log_ctx, AV_LOG_ERROR, "Could not parse link name!\n");
}

/**
 * Parse "filter=params"
 * @arg name a pointer (that need to be free'd after use) to the name of the
 *           filter
 * @arg ars  a pointer (that need to be free'd after use) to the args of the
 *           filter
 */
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static AVFilterContext *parse_filter(const char **buf, AVFilterGraph *graph, int index)
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{
    char *name, *opts;
    name = consume_string(buf);

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    if(**buf == '=') {
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        (*buf)++;
        opts = consume_string(buf);
    } else {
        opts = NULL;
    }

    return create_filter(graph, index, name, opts);
}

enum LinkType {
    LinkTypeIn,
    LinkTypeOut,
};

/**
 * A linked-list of the inputs/outputs of the filter chain.
 */
typedef struct AVFilterInOut {
    enum LinkType type;
    char *name;
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    AVFilterContext *filter;
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    int pad_idx;

    struct AVFilterInOut *next;
} AVFilterInOut;

static void free_inout(AVFilterInOut *head)
{
    while (head) {
        AVFilterInOut *next;
        next = head->next;
        av_free(head);
        head = next;
    }
}

/**
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 * Parse "[a1][link2] ... [etc]"
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 */
static int parse_inouts(const char **buf, AVFilterInOut **inout, int firstpad,
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                        enum LinkType type, AVFilterContext *filter)
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{
    int pad = firstpad;
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    while (**buf == '[') {
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        AVFilterInOut *inoutn = av_malloc(sizeof(AVFilterInOut));
        parse_link_name(buf, &inoutn->name);
        inoutn->type = type;
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        inoutn->filter = filter;
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        inoutn->pad_idx = pad++;
        inoutn->next = *inout;
        *inout = inoutn;
    }
    return pad;
}

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static const char *skip_inouts(const char *buf)
{
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    while (*buf == '[') {
        buf += strcspn(buf, "]");
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        buf++;
    }
    return buf;
}


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/**
 * Parse a string describing a filter graph.
 */
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int avfilter_parse_graph(AVFilterGraph *graph, const char *filters,
                         AVFilterContext *in, int inpad,
                         AVFilterContext *out, int outpad)
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{
    AVFilterInOut *inout=NULL;
    AVFilterInOut  *head=NULL;

    int index = 0;
    char chr = 0;
    int pad = 0;
    int has_out = 0;

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    AVFilterContext *last_filt = NULL;
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    consume_whitespace(&filters);

    do {
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        AVFilterContext *filter;
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        int oldpad = pad;
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        const char *inouts = filters;
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        // We need to parse the inputs of the filter after we create it, so
        // skip it by now
        filters = skip_inouts(filters);
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        if(!(filter = parse_filter(&filters, graph, index)))
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            goto fail;

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        pad = parse_inouts(&inouts, &inout, chr == ',', LinkTypeIn, filter);

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        // If the first filter has an input and none was given, it is
        // implicitly the input of the whole graph.
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        if(pad == 0 && filter->input_count == 1) {
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            if(link_filter(in, inpad, filter, 0))
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                goto fail;
        }

        if(chr == ',') {
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            if(link_filter(last_filt, oldpad, filter, 0) < 0)
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                goto fail;
        }
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        pad = parse_inouts(&filters, &inout, 0, LinkTypeOut, filter);
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        chr = *filters++;
        index++;
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        last_filt = filter;
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    } while (chr == ',' || chr == ';');

    head = inout;
    for (; inout != NULL; inout = inout->next) {
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        if(inout->filter == NULL)
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            continue; // Already processed

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        if(!strcmp(inout->name, "in")) {
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            if(link_filter(in, inpad, inout->filter, inout->pad_idx))
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                goto fail;
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        } else if(!strcmp(inout->name, "out")) {
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            has_out = 1;

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            if(link_filter(inout->filter, inout->pad_idx, out, outpad))
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                goto fail;

        } else {
            AVFilterInOut *p, *src, *dst;
            for (p = inout->next;
                 p && strcmp(p->name,inout->name); p = p->next);

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            if(!p) {
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                av_log(&log_ctx, AV_LOG_ERROR, "Unmatched link: %s.\n",
                       inout->name);
                goto fail;
            }

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            if(p->type == LinkTypeIn && inout->type == LinkTypeOut) {
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                src = inout;
                dst = p;
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            } else if(p->type == LinkTypeOut && inout->type == LinkTypeIn) {
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                src = p;
                dst = inout;
            } else {
                av_log(&log_ctx, AV_LOG_ERROR, "Two links named '%s' are either both input or both output\n",
                       inout->name);
                goto fail;
            }

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            if(link_filter(src->filter, src->pad_idx, dst->filter, dst->pad_idx) < 0)
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                goto fail;

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            src->filter = NULL;
            dst->filter = NULL;
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        }
    }

    free_inout(head);

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    if(!has_out) {
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        if(link_filter(last_filt, pad, out, outpad))
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            goto fail;
    }

    return 0;

 fail:
    free_inout(head);
    avfilter_destroy_graph(graph);
    return -1;
}