asrc_anullsrc.c 3.13 KB
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/*
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * 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.
 *
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 * Libav is distributed in the hope that it will be useful,
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 * 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
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * null audio source
 */

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#include <inttypes.h>
#include <stdio.h>

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#include "avfilter.h"
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#include "internal.h"
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#include "libavutil/audioconvert.h"
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#include "libavutil/internal.h"
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typedef struct {
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    uint64_t channel_layout;
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    int64_t sample_rate;
} ANullContext;

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static int init(AVFilterContext *ctx, const char *args)
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{
    ANullContext *priv = ctx->priv;
    char channel_layout_str[128] = "";

    priv->sample_rate = 44100;
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    priv->channel_layout = AV_CH_LAYOUT_STEREO;
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    if (args)
        sscanf(args, "%"PRId64":%s", &priv->sample_rate, channel_layout_str);

    if (priv->sample_rate < 0) {
        av_log(ctx, AV_LOG_ERROR, "Invalid negative sample rate: %"PRId64"\n", priv->sample_rate);
        return AVERROR(EINVAL);
    }

    if (*channel_layout_str)
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        if (!(priv->channel_layout = av_get_channel_layout(channel_layout_str))
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            && sscanf(channel_layout_str, "%"PRId64, &priv->channel_layout) != 1) {
            av_log(ctx, AV_LOG_ERROR, "Invalid value '%s' for channel layout\n",
                   channel_layout_str);
            return AVERROR(EINVAL);
        }

    return 0;
}

static int config_props(AVFilterLink *outlink)
{
    ANullContext *priv = outlink->src->priv;
    char buf[128];
    int chans_nb;

    outlink->sample_rate = priv->sample_rate;
    outlink->channel_layout = priv->channel_layout;

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    chans_nb = av_get_channel_layout_nb_channels(priv->channel_layout);
    av_get_channel_layout_string(buf, sizeof(buf), chans_nb, priv->channel_layout);
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    av_log(outlink->src, AV_LOG_VERBOSE,
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           "sample_rate:%"PRId64 " channel_layout:%"PRId64 " channel_layout_description:'%s'\n",
           priv->sample_rate, priv->channel_layout, buf);

    return 0;
}

static int request_frame(AVFilterLink *link)
{
    return -1;
}

AVFilter avfilter_asrc_anullsrc = {
    .name        = "anullsrc",
    .description = NULL_IF_CONFIG_SMALL("Null audio source, never return audio frames."),

    .init        = init,
    .priv_size   = sizeof(ANullContext),

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    .inputs      = (const AVFilterPad[]) {{ .name = NULL}},
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    .outputs     = (const AVFilterPad[]) {{ .name = "default",
                                            .type = AVMEDIA_TYPE_AUDIO,
                                            .config_props = config_props,
                                            .request_frame = request_frame, },
                                          { .name = NULL}},
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};